Reference

Copyright © 2006- 2009 Novell, Inc.

Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with the Invariant Section being this copyright notice and license. A copy of the license is included in the section entitled “GNU Free Documentation License”.

SUSE®, openSUSE®, the openSUSE® logo, Novell®, the Novell® logo, the N® logo, are registered trademarks of Novell, Inc. in the United States and other countries. Linux* is a registered trademark of Linus Torvalds. All other third party trademarks are the property of their respective owners. A trademark symbol (® , ™, etc.) denotes a Novell trademark; an asterisk (*) denotes a third-party trademark.

All information found in this book has been compiled with utmost attention to detail. However, this does not guarantee complete accuracy. Neither Novell, Inc., SUSE LINUX Products GmbH, the authors, nor the translators shall be held liable for possible errors or the consequences thereof.

About This Guide

This manual gives you a general understanding of openSUSE®. It is intended mainly for system administrators and home users with basic system administration knowledge. Check out the various parts of this manual for a selection of applications needed in everyday life and in-depth descriptions of advanced installation and configuration scenarios.

Advanced Deployment Scenarios

Learn how to deploy openSUSE from a remote location and become acquainted with complex disk setup scenarios.

Managing and Updating Software

Understand how to install or remove software with either YaST or using the command line, how to use the 1-Click-Install feature, and how to keep your system up-to-date.

Administration

Learn how to configure and upgrade your openSUSE, how to administrate your system in text mode, and get to know some important utilities for Linux administrators.

System

Get an introduction to the components of your Linux system and a deeper understanding of their interaction.

Services

Learn how to configure the various network and file services that come with openSUSE.

Mobility

Get an introduction to mobile computing with openSUSE, get to know the various options for wireless computing and power management.

Many chapters in this manual contain links to additional documentation resources. These include additional documentation that is available on the system, as well as documentation available on the Internet.

For an overview of the documentation available for your product and the latest documentation updates, refer to http://www.novell.com/documentation/opensuse112 or to the following section.

Available Documentation

We provide HTML and PDF versions of our books in different languages.

“Start-Up” (↑Start-Up)

Guides you through the installation and basic configuration of your system. For newcomers, the manual also introduces basic Linux concepts such as the file system, the user concept and access permissions and gives an overview of the features openSUSE offers to support mobile computing. Provides help and advice in troubleshooting.

“KDE User Guide” (↑KDE User Guide)

Introduces the KDE desktop of openSUSE. It guides you through using and configuring the desktop and helps you perform key tasks. It is intended mainly for users who want to make efficient use of KDE as their default desktop.

“GNOME User Guide” (↑GNOME User Guide)

Introduces the GNOME desktop of openSUSE. It guides you through using and configuring the desktop and helps you perform key tasks. It is intended mainly for end users who want to make efficient use of GNOME desktop as their default desktop.

“Application Guide” (↑Application Guide)

Learn how to use and configure key desktop applications on openSUSE. This guide introduces browsers and e-mail clients as well as office applications and collaboration tools. It also covers graphics and multimedia applications.

Reference

Gives you a general understanding of openSUSE and covers advanced system administration tasks. It is intended mainly for system administrators and home users with basic system administration knowledge. It provides detailed information about advanced deployment scenarios, administration of your system, the interaction of key system components and the set-up of various network and file services openSUSE offers.

“Security Guide” (↑Security Guide)

Introduces basic concepts of system security, covering both local and network security aspects. Shows how to make use of the product inherent security software like Novell AppArmor (which lets you specify per program which files the program may read, write, and execute) or the auditing system that reliably collects information about any security-relevant events.

In addition to the comprehensive manuals, several quick start guides are available:

“KDE Quick Start” (↑Quick Start Manuals)

Gives a short introduction to the KDE desktop and some key applications running on it.

“GNOME Quick Start” (↑Quick Start Manuals)

Gives a short introduction to the GNOME desktop and some key applications running on it.

“Installation Quick Start” (↑Quick Start Manuals)

Lists the system requirements and guides you step-by-step through the installation of openSUSE from DVD, or from an ISO image.

Novell AppArmor Quick Start

Helps you understand the main concepts behind Novell® AppArmor.

Find HTML versions of most product manuals in your installed system under /usr/share/doc/manual or in the help centers of your desktop. Find the latest documentation updates at http://www.novell.com/documentation where you can download PDF or HTML versions of the manuals for your product.

Feedback

Several feedback channels are available:

To report bugs for a product component or to submit enhancement requests, please use https://bugzilla.novell.com/. If you are new to Bugzilla, you might find the Submitting Bug Reports article—available under http://en.opensuse.org/Submitting_Bug_Reports helpful. Frequently asked questions on reporting bugs are available under http://en.opensuse.org/Bug_Reporting_FAQ.

We want to hear your comments and suggestions about this manual and the other documentation included with this product. Please use the User Comments feature at the bottom of each page of the online documentation and enter your comments there.

Documentation Conventions

The following typographical conventions are used in this manual:

/etc/passwd: directory names and filenames

placeholder: replace placeholder with the actual value

PATH: the environment variable PATH

ls, --help: commands, options, and parameters

user: users or groups

Alt, Alt+F1: a key to press or a key combination; keys are shown in uppercase as on a keyboard

File, File+Save As: menu items, buttons

Dancing Penguins (Chapter Penguins, ↑Another Manual): This is a reference to a chapter in another manual.

About the Making of This Manual

This book is written in Novdoc, a subset of DocBook (see http://www.docbook.org). The XML source files were validated by xmllint, processed by xsltproc, and converted into XSL-FO using a customized version of Norman Walsh's stylesheets. The final PDF is formatted through XEP from RenderX. The open source tools and the environment used to build this manual are available in the package susedoc that is shipped with openSUSE.

Source Code

The source code of openSUSE is publicly available. To download the source code, proceed as outlined under http://www.novell.com/products/suselinux/source_code.html. If requested we send you the source code on a DVD. We need to charge a $15 or €15 fee for creation, handling and postage. To request a DVD of the source code, send an e-mail to sourcedvd@suse.de or mail the request to:

  SUSE Linux Products GmbH
  Product Management
  openSUSE
  Maxfeldstr. 5
  D-90409 Nürnberg
  Germany

Acknowledgments

With a lot of voluntary commitment, the developers of Linux cooperate on a global scale to promote the development of Linux. We thank them for their efforts—this distribution would not exist without them. Furthermore, we thank Frank Zappa and Pawar. Special thanks, of course, goes to Linus Torvalds.

Have a lot of fun!

Your SUSE Team

Part I. Advanced Deployment Scenarios

Chapter 1. Remote Installation

openSUSE® can be installed in several different ways. As well as the usual media installation covered in “Installation with YaST” (↑Start-Up), you can choose from various network-based approaches or even take a completely hands-off approach to the installation of openSUSE.

Each method is introduced by means of two short check lists: one listing the prerequisites for this method and the other illustrating the basic procedure. More detail is then provided for all the techniques used in these installation scenarios.

Note

In the following sections, the system to hold your new openSUSE installation is referred to as target system or installation target. The term repository (previously called “installation source”) is used for all sources of installation data. This includes physical media, such as CD and DVD, and network servers distributing the installation data in your network.

Installation Scenarios for Remote Installation

This section introduces the most common installation scenarios for remote installations. For each scenario, carefully check the list of prerequisites and follow the procedure outlined for this scenario. If in need of detailed instructions for a particular step, follow the links provided for each one of them.

Simple Remote Installation via VNC—Static Network Configuration

This type of installation still requires some degree of physical access to the target system to boot for installation. The installation itself is entirely controlled by a remote workstation using VNC to connect to the installation program. User interaction is required as with the manual installation in “Installation with YaST” (↑Start-Up).

For this type of installation, make sure that the following requirements are met:

Remote repository: NFS, HTTP, FTP, or SMB with working network connection.

Target system with working network connection.

Controlling system with working network connection and VNC viewer software or Java-enabled browser (Firefox, Konqueror, Internet Explorer, or Opera).

Physical boot medium (CD, DVD, or USB flash drive) for booting the target system.

Valid static IP addresses already assigned to the repository and the controlling system.

Valid static IP address to assign to the target system.

To perform this kind of installation, proceed as follows:

Set up the repository as described in Section “Setting Up the Server Holding the Installation Sources”. Choose an NFS, HTTP, or FTP network server. For an SMB repository, refer to Section “Managing an SMB Repository”.

Boot the target system using the first CD, DVD or a USB flash drive of the openSUSE media kit.

When the boot screen of the target system appears, use the boot options prompt to set the appropriate VNC options and the address of the repository. This is described in detail in Section “Booting the Target System for Installation”.

The target system boots to a text-based environment, giving the network address and display number under which the graphical installation environment can be addressed by any VNC viewer application or browser. VNC installations announce themselves over OpenSLP and if the firewall settings permit, they can be found using Konqueror in service:/ or slp:/ mode.

On the controlling workstation, open a VNC viewing application or Web browser and connect to the target system as described in Section “VNC Installation”.

Perform the installation as described in “Installation with YaST” (↑Start-Up). Reconnect to the target system after it reboots for the final part of the installation.

Finish the installation.

Simple Remote Installation via VNC—Dynamic Network Configuration

This type of installation still requires some degree of physical access to the target system to boot for installation. The network configuration is made with DHCP. The installation itself is entirely controlled from a remote workstation using VNC to connect to the installer, but still requires user interaction for the actual configuration efforts.

For this type of installation, make sure that the following requirements are met:

Remote repository: NFS, HTTP, FTP, or SMB with working network connection.

Target system with working network connection.

Controlling system with working network connection and VNC viewer software or Java-enabled browser (Firefox, Konqueror, Internet Explorer, or Opera).

Physical boot medium (CD, DVD, USB flash drive, or custom boot disk) for booting the target system.

Running DHCP server providing IP addresses.

To perform this kind of installation, proceed as follows:

Set up the repository as described in Section “Setting Up the Server Holding the Installation Sources”. Choose an NFS, HTTP, or FTP network server. For an SMB repository, refer to Section “Managing an SMB Repository”.

Boot the target system using the first CD, DVD or USB flash drive of the openSUSE media kit.

When the boot screen of the target system appears, use the boot options prompt to set the appropriate VNC options and the address of the repository. This is described in detail in Section “Booting the Target System for Installation”.

The target system boots to a text-based environment, giving the network address and display number under which the graphical installation environment can be addressed by any VNC viewer application or browser. VNC installations announce themselves over OpenSLP and if the firewall settings permit, they can be found using Konqueror in service:/ or slp:/ mode.

On the controlling workstation, open a VNC viewing application or Web browser and connect to the target system as described in Section “VNC Installation”.

Perform the installation as described in “Installation with YaST” (↑Start-Up). Reconnect to the target system after it reboots for the final part of the installation.

Finish the installation.

Remote Installation via VNC—PXE Boot and Wake on LAN

This type of installation is completely hands-off. The target machine is started and booted remotely. User interaction is only needed for the actual installation. This approach is suitable for cross-site deployments.

To perform this type of installation, make sure that the following requirements are met:

Remote repository: NFS, HTTP, FTP, or SMB with working network connection.

TFTP server.

Running DHCP server for your network.

Target system capable of PXE boot, networking, and Wake on LAN, plugged in and connected to the network.

Controlling system with working network connection and VNC viewer software or Java-enabled browser (Firefox, Konqueror, Internet Explorer, or Opera).

To perform this type of installation, proceed as follows:

Set up the repository as described in Section “Setting Up the Server Holding the Installation Sources”. Choose an NFS, HTTP, or FTP network server or configure an SMB repository as described in Section “Managing an SMB Repository”.

Set up a TFTP server to hold a boot image that can be pulled by the target system. This is described in Section “Setting Up a TFTP Server”.

Set up a DHCP server to provide IP addresses to all machines and reveal the location of the TFTP server to the target system. This is described in Section “Setting Up a DHCP Server”.

Prepare the target system for PXE boot. This is described in further detail in Section “Preparing the Target System for PXE Boot”.

Initiate the boot process of the target system using Wake on LAN. This is described in Section “Wake on LAN”.

On the controlling workstation, open a VNC viewing application or Web browser and connect to the target system as described in Section “VNC Installation”.

Perform the installation as described in “Installation with YaST” (↑Start-Up). Reconnect to the target system after it reboots for the final part of the installation.

Finish the installation.

Simple Remote Installation via SSH—Static Network Configuration

This type of installation still requires some degree of physical access to the target system to boot for installation and to determine the IP address of the installation target. The installation itself is entirely controlled from a remote workstation using SSH to connect to the installer. User interaction is required as with the regular installation described in “Installation with YaST” (↑Start-Up).

For this type of installation, make sure that the following requirements are met:

Remote repository: NFS, HTTP, FTP, or SMB with working network connection.

Target system with working network connection.

Controlling system with working network connection and working SSH client software.

Physical boot medium (CD, DVD, USB flash drive, or custom boot disk) for the target system.

Valid static IP addresses already assigned to the repository and the controlling system.

Valid static IP address to assign to the target system.

To perform this kind of installation, proceed as follows:

Set up the repository as described in Section “Setting Up the Server Holding the Installation Sources”. Choose an NFS, HTTP, or FTP network server. For an SMB repository, refer to Section “Managing an SMB Repository”.

Boot the target system using the first CD, DVD, or USB flash drive of the openSUSE media kit.

When the boot screen of the target system appears, use the boot options prompt to set the appropriate parameters for network connection, address of the repository, and SSH enablement. This is described in detail in Section “Using Custom Boot Options”.

The target system boots to a text-based environment, giving the network address under which the graphical installation environment can be addressed by any SSH client.

On the controlling workstation, open a terminal window and connect to the target system as described in Section “Connecting to the Installation Program”.

Perform the installation as described in “Installation with YaST” (↑Start-Up). Reconnect to the target system after it reboots for the final part of the installation.

Finish the installation.

Simple Remote Installation via SSH—Dynamic Network Configuration

This type of installation still requires some degree of physical access to the target system to boot for installation and determine the IP address of the installation target. The installation itself is entirely controlled from a remote workstation using VNC to connect to the installer, but still requires user interaction for the actual configuration efforts.

For this type of installation, make sure that the following requirements are met:

Remote repository: NFS, HTTP, FTP, or SMB with working network connection.

Target system with working network connection.

Controlling system with working network connection and working SSH client software.

Physical boot medium (CD, DVD, or USB flash drive) for booting the target system.

Running DHCP server providing IP addresses.

To perform this kind of installation, proceed as follows:

Set up the repository source as described in Section “Setting Up the Server Holding the Installation Sources”. Choose an NFS, HTTP, or FTP network server. For an SMB repository, refer to Section “Managing an SMB Repository”.

Boot the target system using the first CD, DVD or USB flash drive of the openSUSE media kit.

When the boot screen of the target system appears, use the boot options prompt to pass the appropriate parameters for network connection, location of the installation source, and SSH enablement. See Section “Using Custom Boot Options” for detailed instructions on the use of these parameters.

The target system boots to a text-based environment, giving you the network address under which the graphical installation environment can be addressed by any SSH client.

On the controlling workstation, open a terminal window and connect to the target system as described in Section “Connecting to the Installation Program”.

Perform the installation as described in “Installation with YaST” (↑Start-Up). Reconnect to the target system after it reboots for the final part of the installation.

Finish the installation.

Remote Installation via SSH—PXE Boot and Wake on LAN

This type of installation is completely hands-off. The target machine is started and booted remotely.

To perform this type of installation, make sure that the following requirements are met:

Remote repository: NFS, HTTP, FTP, or SMB with working network connection.

TFTP server.

Running DHCP server for your network, providing a static IP to the host to install.

Target system capable of PXE boot, networking, and Wake on LAN, plugged in and connected to the network.

Controlling system with working network connection and SSH client software.

To perform this type of installation, proceed as follows:

Set up the repository as described in Section “Setting Up the Server Holding the Installation Sources”. Choose an NFS, HTTP, or FTP network server. For the configuration of an SMB repository, refer to Section “Managing an SMB Repository”.

Set up a TFTP server to hold a boot image that can be pulled by the target system. This is described in Section “Setting Up a TFTP Server”.

Set up a DHCP server to provide IP addresses to all machines and reveal the location of the TFTP server to the target system. This is described in Section “Setting Up a DHCP Server”.

Prepare the target system for PXE boot. This is described in further detail in Section “Preparing the Target System for PXE Boot”.

Initiate the boot process of the target system using Wake on LAN. This is described in Section “Wake on LAN”.

On the controlling workstation, start an SSH client and connect to the target system as described in Section “SSH Installation”.

Perform the installation as described in “Installation with YaST” (↑Start-Up). Reconnect to the target system after it reboots for the final part of the installation.

Finish the installation.

Setting Up the Server Holding the Installation Sources

Depending on the operating system running on the machine to use as the network installation source for openSUSE, there are several options for the server configuration. The easiest way to set up an installation server is to use YaST on openSUSE 11.1 and higher.

Tip

You can even use a Microsoft Windows machine as the installation server for your Linux deployment. See Section “Managing an SMB Repository” for details.

Setting Up an Installation Server Using YaST

YaST offers a graphical tool for creating network repositories. It supports HTTP, FTP, and NFS network installation servers.

Log in as root to the machine that should act as installation server.

Install the yast2-instserver package.

Start YaST+Miscellaneous+Installation Server.

Select the server type (HTTP, FTP, or NFS). The selected server service is started automatically every time the system starts. If a service of the selected type is already running on your system and you want to configure it manually for the server, deactivate the automatic configuration of the server service with Do Not Configure Any Network Services. In both cases, define the directory in which the installation data should be made available on the server.

Configure the required server type. This step relates to the automatic configuration of server services. It is skipped when automatic configuration is deactivated.

Define an alias for the root directory of the FTP or HTTP server on which the installation data should be found. The installation source will later be located under ftp://Server-IP/Alias/Name (FTP) or under http://Server-IP/Alias/Name (HTTP). Name stands for the name of the repository, which is defined in the following step. If you selected NFS in the previous step, define wild cards and export options. The NFS server will be accessible under nfs://Server-IP/Name. Details of NFS and exports can be found in Chapter 26, Sharing File Systems with NFS.

Firewall Settings

Make sure that the firewall settings of your server system allow traffic on the ports for HTTP, NFS, and FTP. If they currently do not, enable Open Port in Firewall or check Firewall Details first.

Configure the repository. Before the installation media are copied to their destination, define the name of the repository (ideally, an easily remembered abbreviation of the product and version). YaST allows providing ISO images of the media instead of copies of the installation CDs. If you want this, activate the relevant check box and specify the directory path under which the ISO files can be found locally. Depending on the product to distribute using this installation server, it might be that more add-on CDs or service pack CDs are required and should be added as extra repositories. To announce your installation server in the network via OpenSLP, activate the appropriate option.

Tip

Consider announcing your repository via OpenSLP if your network setup supports this option. This saves you from entering the network installation path on every target machine. The target systems are just booted using the SLP boot option and find the network repository without any further configuration. For details on this option, refer to Section “Booting the Target System for Installation”.

Upload the installation data. The most lengthy step in configuring an installation server is copying the actual installation CDs. Insert the media in the sequence requested by YaST and wait for the copying procedure to end. When the sources have been fully copied, return to the overview of existing repositories and close the configuration by selecting Finish.

Your installation server is now fully configured and ready for service. It is automatically started every time the system is started. No further intervention is required. You only need to configure and start this service correctly by hand if you have deactivated the automatic configuration of the selected network service with YaST as an initial step.

To deactivate a repository, select the repository to remove then select Delete. The installation data are removed from the system. To deactivate the network service, use the respective YaST module.

If your installation server needs to provide the installation data for more than one product of product version, start the YaST installation server module and select Add in the overview of existing repositories to configure the new repository.

Setting Up an NFS Repository Manually

Setting up an NFS source for installation is basically done in two steps. In the first step, create the directory structure holding the installation data and copy the installation media over to this structure. Second, export the directory holding the installation data to the network.

To create a directory to hold the installation data, proceed as follows:

Log in as root.

Create a directory that will later hold all installation data and change into this directory. For example:

mkdir install/product/productversion

cd install/product/productversion

Replace product with an abbreviation of the product name and productversion with a string that contains the product name and version.

For each CD or DVD contained in the media kit execute the following commands:

Copy the entire content of the installation CD or DVD into the installation server directory:

cp -a /media/path_to_your_CD-ROM_drive .

Replace path_to_your_CD-ROM_drive with the actual path under which your CD or DVD drive is addressed. Depending on the type of drive used in your system, this can be cdrom, cdrecorder, dvd, or dvdrecorder.

Rename the directory to the CD number:

mv path_to_your_CD-ROM_drive CDx

Replace x with the actual number of your CD.

On openSUSE, you can export the repository with NFS using YaST. Proceed as follows:

Log in as root.

Start YaST+Network Services+NFS Server.

Select Start and Open Port in Firewall and click Next.

Select Add Directory and browse for the directory containing the installation sources, in this case, productversion.

Select Add Host and enter the hostnames of the machines to which to export the installation data. Instead of specifying hostnames here, you could also use wild cards, ranges of network addresses, or just the domain name of your network. Enter the appropriate export options or leave the default, which works fine in most setups. For more information about the syntax used in exporting NFS shares, read the exports man page.

Click Finish. The NFS server holding the openSUSE repository is automatically started and integrated into the boot process.

If you prefer manually exporting the repository via NFS instead of using the YaST NFS Server module, proceed as follows:

Log in as root.

Open the file /etc/exports and enter the following line:

/productversion *(ro,root_squash,sync)

This exports the directory /productversion to any host that is part of this network or to any host that can connect to this server. To limit the access to this server, use netmasks or domain names instead of the general wild card *. Refer to the export man page for details. Save and exit this configuration file.

To add the NFS service to the list of servers started during system boot, execute the following commands:

insserv /etc/init.d/nfsserver
insserv /etc/init.d/portmap

Start the NFS server with rcnfsserver start. If you need to change the configuration of your NFS server later, modify the configuration file and restart the NFS daemon with rcnfsserver restart.

Announcing the NFS server via OpenSLP makes its address known to all clients in your network.

Log in as root.

Enter the directory /etc/slp.reg.d/.

Create a configuration file called install.suse.nfs.reg containing the following lines:

# Register the NFS Installation Server
service:install.suse:nfs://$HOSTNAME/path_to_repository/CD1,en,65535
description=NFS Repository

Replace path_to_repository with the actual path to the installation source on your server.

Save this configuration file and start the OpenSLP daemon with rcslpd start.

For more information about OpenSLP, refer to the package documentation located under /usr/share/doc/packages/openslp/ or refer to Chapter 22, SLP Services in the Network. More Information about NFS is found in Chapter 26, Sharing File Systems with NFS.

Setting Up an FTP Repository Manually

Creating an FTP repository is very similar to creating an NFS repository. An FTP repository can be announced over the network using OpenSLP as well.

Create a directory holding the installation sources as described in Section “Setting Up an NFS Repository Manually”.

Configure the FTP server to distribute the contents of your installation directory:

Log in as root and install the package vsftpd using the YaST package manager.

Enter the FTP server root directory:

cd /srv/ftp

Create a subdirectory holding the installation sources in the FTP root directory:

mkdir repository

Replace replaceable with the product name.

Mount the contents of the installation repository into the change root environment of the FTP server:

mount --bind path_to_repository /srv/ftp/instsource

Replace path_to_repository and repository with values matching your setup. If you need to make this permanent, add it to /etc/fstab.

Start vsftpd with vsftpd.

Announce the repository via OpenSLP, if this is supported by your network setup:

Create a configuration file called install.suse.ftp.reg under /etc/slp.reg.d/ that contains the following lines:

# Register the FTP Installation Server
service:install.suse:ftp://$HOSTNAME/repository/CD1,en,65535
description=FTP Repository

Replace repository with the actual name to the repository directory on your server. The service: line should be entered as one continuous line.

Save this configuration file and start the OpenSLP daemon with rcslpd start.

Configuring an FTP Server with YaST

If you prefer using YaST over manually configuring the FTP installation server, refer to Chapter 29, Setting up an FTP server with YaST for more information on how to use the YaST FTP server module.

Setting Up an HTTP Repository Manually

Creating an HTTP repository is very similar to creating an NFS repository. An HTTP repository can be announced over the network using OpenSLP as well.

Create a directory holding the installation sources as described in Section “Setting Up an NFS Repository Manually”.

Configure the HTTP server to distribute the contents of your installation directory:

Install the Web server Apache as described in Section “Installation”.

Enter the root directory of the HTTP server (/srv/www/htdocs) and create the subdirectory that will hold the installation sources:

mkdir repository

Replace repository with the product name.

Create a symbolic link from the location of the installation sources to the root directory of the Web server (/srv/www/htdocs):

ln -s /path_to_repository /srv/www/htdocs/repository

Modify the configuration file of the HTTP server (/etc/apache2/default-server.conf) to make it follow symbolic links. Replace the following line:

Options None

with

Options Indexes FollowSymLinks

Reload the HTTP server configuration using rcapache2 reload.

Announce the repository via OpenSLP, if this is supported by your network setup:

Create a configuration file called install.suse.http.reg under /etc/slp.reg.d/ that contains the following lines:

# Register the HTTP Installation Server
service:install.suse:http://$HOSTNAME/repository/CD1/,en,65535
description=HTTP Repository

Replace repository with the actual path to the repository on your server. The service: line should be entered as one continuous line.

Save this configuration file and start the OpenSLP daemon using rcslpd restart.

Managing an SMB Repository

Using SMB, you can import the installation sources from a Microsoft Windows server and start your Linux deployment even with no Linux machine around.

To set up an exported Windows Share holding your openSUSE repository, proceed as follows:

Log in to your Windows machine.

Start Explorer and create a new folder that will hold the entire installation tree and name it INSTALL, for example.

Export this share according the procedure outlined in your Windows documentation.

Enter this share and create a subfolder, called product. Replace product with the actual product name.

Enter the INSTALL/product folder and copy each CD or DVD to a separate folder, such as CD1 and CD2.

To use a SMB mounted share as a repository, proceed as follows:

Boot the installation target.

Select Installation.

Press F4 for a selection of the repository.

Choose SMB and enter the Windows machine's name or IP address, the share name (INSTALL/product/CD1, in this example), username, and password.

After you hit Enter, YaST starts and you can perform the installation.

Using ISO Images of the Installation Media on the Server

Instead of copying physical media into your server directory manually, you can also mount the ISO images of the installation media into your installation server and use them as a repository. To set up an HTTP, NFS or FTP server that uses ISO images instead of media copies, proceed as follows:

Download the ISO images and save them to the machine to use as the installation server.

Log in as root.

Choose and create an appropriate location for the installation data, as described in Section “Setting Up an NFS Repository Manually”, Section “Setting Up an FTP Repository Manually”, or Section “Setting Up an HTTP Repository Manually”.

Create subdirectories for each CD or DVD.

To mount and unpack each ISO image to the final location, issue the following command:

mount -o loop path_to_iso path_to_repository/product/mediumx

Replace path_to_iso with the path to your local copy of the ISO image, path_to_repository with the source directory of your server, product with the product name, and mediumx with the type (CD or DVD) and number of media you are using.

Repeat the previous step to mount all ISO images needed for your product.

Start your installation server as usual, as described in Section “Setting Up an NFS Repository Manually”, Section “Setting Up an FTP Repository Manually”, or Section “Setting Up an HTTP Repository Manually”.

To automatically mount the ISO images at boot time, add the respective mount entries to /etc/fstab. An entry according to the previous example would look like the following:

path_to_iso path_to_repository/product
    medium auto loop

Preparing the Boot of the Target System

This section covers the configuration tasks needed in complex boot scenarios. It contains ready-to-apply configuration examples for DHCP, PXE boot, TFTP, and Wake on LAN.

Setting Up a DHCP Server

There are two ways to set up a DHCP server. For openSUSE, YaST provides a graphical interface to the process. Users can also manually edit the configuration files. For more information about DHCP servers, see also Chapter 24, DHCP.

Setting Up a DHCP Server with YaST

To announce the TFTP server's location to the network clients and specify the boot image file the installation target should use, add two declarations to your DHCP server configuration.

Log in as root to the machine hosting the DHCP server.

Start YaST+Network Services+DHCP Server.

Complete the setup wizard for basic DHCP server setup.

Select Expert Settings and select Yes when warned about leaving the start-up dialog.

In the Configured Declarations dialog, select the subnet in which the new system should be located and click Edit.

In the Subnet Configuration dialog select Add to add a new option to the subnet's configuration.

Select filename and enter pxelinux.0 as the value.

Add another option (next-server) and set its value to the address of the TFTP server.

Select OK and Finish to complete the DHCP server configuration.

To configure DHCP to provide a static IP address to a specific host, enter the Expert Settings of the DHCP server configuration module (Step 4) and add a new declaration of the host type. Add the options hardware and fixed-address to this host declaration and provide the appropriate values.

Setting Up a DHCP Server Manually

All the DHCP server needs to do, apart from providing automatic address allocation to your network clients, is to announce the IP address of the TFTP server and the file that needs to be pulled in by the installation routines on the target machine.

Log in as root to the machine hosting the DHCP server.

Append the following lines to a subnet configuration of your DHCP server's configuration file located under /etc/dhcpd.conf:

subnet 192.168.1.0 netmask 255.255.255.0 {
  range dynamic-bootp 192.168.1.200 192.168.1.228;
  # PXE related stuff
  #
  # "next-server" defines the tftp server that will be used
  next-server ip_tftp_server:
  #
  # "filename" specifies the pxelinux image on the tftp server
  # the server runs in chroot under /srv/tftpboot
  filename  "pxelinux.0";
}

Replace ip_of_the_tftp_server with the actual IP address of the TFTP server. For more information about the options available in dhcpd.conf, refer to the dhcpd.conf manual page.

Restart the DHCP server by executing rcdhcpd restart.

If you plan on using SSH for the remote control of a PXE and Wake on LAN installation, explicitly specify the IP address DHCP should provide to the installation target. To achieve this, modify the above-mentioned DHCP configuration according to the following example:

group {
  # PXE related stuff
  #
  # "next-server" defines the tftp server that will be used
  next-server ip_tftp_server:
  #
  # "filename" specifies the pxelinux image on the tftp server
  # the server runs in chroot under /srv/tftpboot
  filename "pxelinux.0";
  host test {
    hardware ethernet mac_address;
    fixed-address some_ip_address;
    }
}

The host statement introduces the hostname of the installation target. To bind the hostname and IP address to a specific host, you must know and specify the system's hardware (MAC) address. Replace all the variables used in this example with the actual values that match your environment.

After restarting the DHCP server, it provides a static IP to the host specified, enabling you to connect to the system via SSH.

Setting Up a TFTP Server

Set up a TFTP server with YaST or set it up manually on any other Linux operating system that supports xinetd and tftp. The TFTP server delivers the boot image to the target system once it boots and sends a request for it.

Setting Up a TFTP Server Using YaST

Log in as root.

Install the yast2-tftp-server package.

Start YaST+Network Services+TFTP Server and install the requested package.

Click Enable to make sure that the server is started and included in the boot routines. No further action from your side is required to secure this. xinetd starts tftpd at boot time.

Click Open Port in Firewall to open the appropriate port in the firewall running on your machine. If there is no firewall running on your server, this option is not available.

Click Browse to browse for the boot image directory. The default directory /tftpboot is created and selected automatically.

Click Finish to apply your settings and start the server.

Setting Up a TFTP Server Manually

Log in as root and install the packages tftp and xinetd.

If unavailable, create /srv/tftpboot and /srv/tftpboot/pxelinux.cfg directories.

Add the appropriate files needed for the boot image as described in Section “Using PXE Boot”.

Modify the configuration of xinetd located under /etc/xinetd.d/ to make sure that the TFTP server is started on boot:

If it does not exist, create a file called tftp under this directory with touch tftp. Then run chmod 755 tftp.

Open the file tftp and add the following lines:

service tftp
{
        socket_type            = dgram
        protocol               = udp
        wait                   = yes
        user                   = root
        server                 = /usr/sbin/in.tftpd
        server_args            = -s /srv/tftpboot
        disable                = no
}

Save the file and restart xinetd with rcxinetd restart.

Using PXE Boot

Some technical background information as well as PXE's complete specifications are available in the Preboot Execution Environment (PXE) Specification (http://www.pix.net/software/pxeboot/archive/pxespec.pdf).

Change to the directory boot/<architecture>/loader of your installation repository and copy the linux, initrd, message, biostest, and memtest files to the /srv/tftpboot directory by entering the following:

cp -a linux initrd message biostest memtest /srv/tftpboot

Install the syslinux package directly from your installation CDs or DVDs with YaST.

Copy the /usr/share/syslinux/pxelinux.0 file to the /srv/tftpboot directory by entering the following:

cp -a /usr/share/syslinux/pxelinux.0 /srv/tftpboot

Change to the directory of your installation repository and copy the isolinux.cfg file to /srv/tftpboot/pxelinux.cfg/default by entering the following:

cp -a boot/<architecture>/loader/isolinux.cfg /srv/tftpboot/pxelinux.cfg/default

Edit the /srv/tftpboot/pxelinux.cfg/default file and remove the lines beginning with gfxboot, readinfo, and framebuffer.

Insert the following entries in the append lines of the default failsafe and apic labels:

insmod=kernel module

By means of this entry, enter the network kernel module needed to support network installation on the PXE client. Replace kernel module with the appropriate module name for your network device.

netdevice=interface

This entry defines the client's network interface that must be used for the network installation. It is only necessary if the client is equipped with several network cards and must be adapted accordingly. In case of a single network card, this entry can be omitted.

install=nfs://ip_instserver/path_to_repository/CD1

This entry defines the NFS server and the repository for the client installation. Replace ip_instserver with the actual IP address of your installation server. path_to_repository should be replaced with the actual path to the repository. HTTP, FTP, or SMB repositories are addressed in a similar manner, except for the protocol prefix, which should read http, ftp, or smb.

Important

If you need to pass other boot options to the installation routines, such as SSH or VNC boot parameters, append them to the install entry. An overview of parameters and some examples are given in Section “Booting the Target System for Installation”.

Changing Kernel and Initrd Filenames

It is possible to use different filenames for kernel and initrd images. This is useful if you want to provide different operating systems from the same boot server. However, you should be aware that only one dot is permitted in the filenames that are provided by tftp for the pxe boot.

An example /srv/tftpboot/pxelinux.cfg/default file follows. Adjust the protocol prefix for the repository to match your network setup and specify your preferred method of connecting to the installer by adding the vnc and vncpassword or the usessh and sshpassword options to the install entry. The lines separated by \ must be entered as one continuous line without a line break and without the \.

default harddisk

# default
label linux
  kernel linux
  append initrd=initrd ramdisk_size=65536 \
     install=nfs://ip_instserver/path_to_repository/product/DVD1

# repair
label repair
  kernel linux
  append initrd=initrd splash=silent repair=1 showopts

# rescue
label rescue
  kernel linux
  append initrd=initrd ramdisk_size=65536 rescue=1

# bios test
label firmware
  kernel linux
  append initrd=biostest,initrd splash=silent install=exec:/bin/run_biostest showopts

#  memory test
label memtest
  kernel memtest

# hard disk
label harddisk
  localboot 0

implicit     0
display      message
prompt       1
timeout      100

Replace ip_instserver and path_to_repository with the values used in your setup.

The following section serves as a short reference to the PXELINUX options used in this setup. Find more information about the options available in the documentation of the syslinux package located under /usr/share/doc/packages/syslinux/.

PXELINUX Configuration Options

The options listed here are a subset of all the options available for the PXELINUX configuration file.

DEFAULT kernel options...

Sets the default kernel command line. If PXELINUX boots automatically, it acts as if the entries after DEFAULT had been typed in at the boot prompt, except the auto option is automatically added, indicating an automatic boot.

If no configuration file is present or no DEFAULT entry is present in the configuration file, the default is the kernel name “linux” with no options.

APPEND options...

Add one or more options to the kernel command line. These are added for both automatic and manual boots. The options are added at the very beginning of the kernel command line, usually permitting explicitly entered kernel options to override them.

LABEL label KERNEL image APPEND options...

Indicates that if label is entered as the kernel to boot, PXELINUX should instead boot image and the specified APPEND options should be used instead of the ones specified in the global section of the file (before the first LABEL command). The default for image is the same as label and, if no APPEND is given, the default is to use the global entry (if any). Up to 128 LABEL entries are permitted.

Note that GRUB uses the following syntax:

title mytitle
  kernel my_kernel my_kernel_options
  initrd myinitrd

PXELINUX uses the following syntax:

label mylabel
  kernel mykernel
  append myoptions

Labels are mangled as if they were filenames and they must be unique after mangling. For example, the two labels “v2.1.30” and “v2.1.31” would not be distinguishable under PXELINUX because both mangle to the same DOS filename.

The kernel does not have to be a Linux kernel; it can be a boot sector or a COMBOOT file.

APPEND -

Append nothing. APPEND with a single hyphen as argument in a LABEL section can be used to override a global APPEND.

LOCALBOOT type

On PXELINUX, specifying LOCALBOOT 0 instead of a KERNEL option means invoking this particular label and causes a local disk boot instead of a kernel boot.

Argument

Description

0

Perform a normal boot

4

Perform a local boot with the Universal Network Driver Interface (UNDI) driver still resident in memory

5

Perform a local boot with the entire PXE stack, including the UNDI driver, still resident in memory

All other values are undefined. If you do not know what the UNDI or PXE stacks are, specify 0.

TIMEOUT time-out

Indicates how long to wait at the boot prompt until booting automatically, in units of 1/10 second. The time-out is canceled as soon as the user types anything on the keyboard, assuming the user will complete the command begun. A time-out of zero disables the time-out completely (this is also the default). The maximum possible time-out value is 35996 (just less than one hour).

PROMPT flag_val

If flag_val is 0, displays the boot prompt only if Shift or Alt is pressed or Caps Lock or Scroll Lock is set (this is the default). If flag_val is 1, always displays the boot prompt.

F2  filename
F1  filename
..etc...
F9  filename
F10 filename

Displays the indicated file on the screen when a function key is pressed at the boot prompt. This can be used to implement preboot online help (presumably for the kernel command line options). For backward compatibility with earlier releases, F10 can be also entered as F0. Note that there is currently no way to bind filenames to F11 and F12.

Preparing the Target System for PXE Boot

Prepare the system's BIOS for PXE boot by including the PXE option in the BIOS boot order.

BIOS Boot Order

Do not place the PXE option ahead of the hard disk boot option in the BIOS. Otherwise this system would try to reinstall itself every time you boot it.

Preparing the Target System for Wake on LAN

Wake on LAN (WOL) requires the appropriate BIOS option to be enabled prior to the installation. Also, note down the MAC address of the target system. This data is needed to initiate Wake on LAN.

Wake on LAN

Wake on LAN allows a machine to be turned on by a special network packet containing the machine's MAC address. Because every machine in the world has a unique MAC identifier, you do not need to worry about accidentally turning on the wrong machine.

Wake on LAN across Different Network Segments

If the controlling machine is not located in the same network segment as the installation target that should be awakened, either configure the WOL requests to be sent as multicasts or remotely control a machine on that network segment to act as the sender of these requests.

Booting the Target System for Installation

Basically, there are two different ways to customize the boot process for installation apart from those mentioned under Section “Wake on LAN” and Section “Using PXE Boot”. You can either use the default boot options and function keys or use the boot options prompt of the installation boot screen to pass any boot options that the installation kernel might need on this particular hardware.

Using the Default Boot Options

The boot options are described in detail in “Installation with YaST” (↑Start-Up). Generally, just selecting Installation starts the installation boot process.

If problems occur, use Installation—ACPI Disabled or Installation—Safe Settings. For more information about troubleshooting the installation process, refer to “Installation Problems” (Chapter “Common Problems and Their Solutions”, ↑Start-Up).

The menu bar at the bottom screen offers some advanced functionality needed in some setups. Using the F keys, you can specify additional options to pass to the installation routines without having to know the detailed syntax of these parameters (see Section “Using Custom Boot Options”). A detailed description of the available function keys is available at “The Boot Screen” (Chapter “Installation with YaST”, ↑Start-Up).

Using Custom Boot Options

Using the appropriate set of boot options helps facilitate your installation procedure. Many parameters can also be configured later using the linuxrc routines, but using the boot options is easier. In some automated setups, the boot options can be provided with initrd or an info file.

The following table lists all installation scenarios mentioned in this chapter with the required parameters for booting and the corresponding boot options. Just append all of them in the order they appear in this table to get one boot option string that is handed to the installation routines. For example (all in one line):

install=... netdevice=... hostip=...netmask=... vnc=... vncpassword=...

Replace all the values ... in this string with the values appropriate for your setup.

Table 1.1. Installation (Boot) Scenarios Used in This Chapter

Installation Scenario

Parameters Needed for Booting

Boot Options

“Installation with YaST” (↑Start-Up)

None: system boots automatically

None needed

Section “Simple Remote Installation via VNC—Static Network Configuration”

Location of the installation server

Network device

IP address

Netmask

Gateway

VNC enablement

VNC password

install=(nfs,http,​ftp,smb)://path_to_instmedia

netdevice=some_netdevice (only needed if several network devices are available)

hostip=some_ip

netmask=some_netmask

gateway=ip_gateway

vnc=1

vncpassword=some_password

Section “Simple Remote Installation via VNC—Dynamic Network Configuration”

Location of the installation server

VNC enablement

VNC password

install=(nfs,http,​ftp,smb)://path_to_instmedia

vnc=1

vncpassword=some_password

Section “Remote Installation via VNC—PXE Boot and Wake on LAN”

Location of the installation server

Location of the TFTP server

VNC enablement

VNC password

Not applicable; process managed through PXE and DHCP

Section “Simple Remote Installation via SSH—Static Network Configuration”

Location of the installation server

Network device

IP address

Netmask

Gateway

SSH enablement

SSH password

install=(nfs,http,​ftp,smb)://path_to_instmedia

netdevice=some_netdevice (only needed if several network devices are available)

hostip=some_ip

netmask=some_netmask

gateway=ip_gateway

usessh=1

sshpassword=some_password

Section “Simple Remote Installation via SSH—Dynamic Network Configuration”

Location of the installation server

SSH enablement

SSH password

install=(nfs,http,​ftp,smb)://path_to_instmedia

usessh=1

sshpassword=some_password

Section “Remote Installation via SSH—PXE Boot and Wake on LAN”

Location of the installation server

Location of the TFTP server

SSH enablement

SSH password

Not applicable; process managed through PXE and DHCP

More Information about linuxrc Boot Options

Find more information about the linuxrc boot options used for booting a Linux system at http://en.opensuse.org/Linuxrc.

Monitoring the Installation Process

There are several options for remotely monitoring the installation process. If the proper boot options have been specified while booting for installation, either VNC or SSH can be used to control the installation and system configuration from a remote workstation.

VNC Installation

Using any VNC viewer software, you can remotely control the installation of openSUSE from virtually any operating system. This section introduces the setup using a VNC viewer application or a Web browser.

Preparing for VNC Installation

All you need to do on the installation target to prepare for a VNC installation is to provide the appropriate boot options at the initial boot for installation (see Section “Using Custom Boot Options”). The target system boots into a text-based environment and waits for a VNC client to connect to the installation program.

The installation program announces the IP address and display number needed to connect for installation. If you have physical access to the target system, this information is provided right after the system booted for installation. Enter this data when your VNC client software prompts for it and provide your VNC password.

Because the installation target announces itself via OpenSLP, you can retrieve the address information of the installation target via an SLP browser without the need for any physical contact to the installation itself, provided your network setup and all machines support OpenSLP:

Start the KDE file and Web browser Konqueror.

Enter service://yast.installation.suse in the location bar. The target system then appears as an icon in the Konqueror screen. Clicking this icon launches the KDE VNC viewer in which to perform the installation. Alternatively, run your VNC viewer software with the IP address provided and add :1 at the end of the IP address for the display the installation is running on.

Connecting to the Installation Program

Basically, there are two ways to connect to a VNC server (the installation target in this case). You can either start an independent VNC viewer application on any operating system or connect using a Java-enabled Web browser.

Using VNC, you can control the installation of a Linux system from any other operating system, including other Linux flavors, Windows, or Mac OS.

On a Linux machine, make sure that the package tightvnc is installed. On a Windows machine, install the Windows port of this application, which can be obtained at the TightVNC home page (http://www.tightvnc.com/download.html).

To connect to the installation program running on the target machine, proceed as follows:

Start the VNC viewer.

Enter the IP address and display number of the installation target as provided by the SLP browser or the installation program itself:

ip_address:display_number

A window opens on your desktop displaying the YaST screens as in a normal local installation.

Using a Web browser to connect to the installation program makes you totally independent of any VNC software or the underlying operating system. As long as the browser application has Java support enabled, you can use any browser (Firefox, Internet Explorer, Konqueror, Opera, etc.) to perform the installation of your Linux system.

To perform a VNC installation, proceed as follows:

Launch your preferred Web browser.

Enter the following at the address prompt:

http://ip_address_of_target:5801

Enter your VNC password when prompted to do so. The browser window now displays the YaST screens as in a normal local installation.

SSH Installation

Using SSH, you can remotely control the installation of your Linux machine using any SSH client software.

Preparing for SSH Installation

Apart from installing the appropriate software package (OpenSSH for Linux and PuTTY for Windows), you just need to pass the appropriate boot options to enable SSH for installation. See Section “Using Custom Boot Options” for details. OpenSSH is installed by default on any SUSE Linux–based operating system.

Connecting to the Installation Program

Retrieve the installation target's IP address. If you have physical access to the target machine, just take the IP address the installation routine provides at the console after the initial boot. Otherwise take the IP address that has been assigned to this particular host in the DHCP server configuration.

At a command line, enter the following command:

ssh -X root@ip_address_of_target

Replace ip_address_of_target with the actual IP address of the installation target.

When prompted for a username, enter root.

When prompted for the password, enter the password that has been set with the SSH boot option. After you have successfully authenticated, a command line prompt for the installation target appears.

Enter yast to launch the installation program. A window opens showing the normal YaST screens as described in “Installation with YaST” (↑Start-Up).

Chapter 2. Advanced Disk Setup

Sophisticated system configurations require specific disk setups. All common partitioning tasks can be done with YaST. To get persistent device naming with block devices, use the block devices below /dev/disk/by-id or /dev/disk/by-uuid. Logical Volume Management (LVM) is a disk partitioning scheme that is designed to be much more flexible than the physical partitioning used in standard setups. Its snapshot functionality enables easy creation of data backups. Redundant Array of Independent Disks (RAID) offers increased data integrity, performance, and fault tolerance.

Using the YaST Partitioner

With the expert partitioner, shown in Figure 2.1, “The YaST Partitioner”, manually modify the partitioning of one or several hard disks. Partitions can be added, deleted, resized, and edited. Also access the soft RAID and LVM configuration from this YaST module.

Repartitioning the Running System

Although it is possible to repartition your system while it is running, the risk of making a mistake that causes data loss is very high. Try to avoid repartitioning your installed system and always do a complete backup of your data before attempting to do so.

Figure 2.1. The YaST Partitioner

All existing or suggested partitions on all connected hard disks are displayed in the list of Available Storage in the YaST Expert Partitioner dialog. Entire hard disks are listed as devices without numbers, such as /dev/sda. Partitions are listed as parts of these devices, such as /dev/sda1. The size, type, file system, and mount point of the hard disks and their partitions are also displayed. The mount point describes where the partition appears in the Linux file system tree.

Several functional views are available on the left System View menu. Use these views to gather information about existing storage configurations, or to configure functions like RAID, Volume Management, Crypt Files, or NFS.

If you run the expert dialog during installation, any free hard disk space is also listed and automatically selected. To provide more disk space to openSUSE®, free the needed space starting from the bottom toward the top of the list (starting from the last partition of a hard disk toward the first). For example, if you have three partitions, you cannot use the second exclusively for openSUSE and retain the third and first for other operating systems.

Partition Types

Every hard disk has a partition table with space for four entries. Every entry in the partition table corresponds to a primary partition or an extended partition. Only one extended partition entry is allowed, however.

A primary partition simply consists of a continuous range of cylinders (physical disk areas) assigned to a particular operating system. With primary partitions you would be limited to four partitions per hard disk, because more do not fit in the partition table. This is why extended partitions are used. Extended partitions are also continuous ranges of disk cylinders, but an extended partition can be divided into logical partitions itself. Logical partitions do not require entries in the partition table. In other words, an extended partition is a container for logical partitions.

If you need more than four partitions, create an extended partition as the fourth partition (or earlier). This extended partition should span the entire remaining free cylinder range. Then create multiple logical partitions within the extended partition. The maximum number of logical partitions is 15 on SCSI, SATA, and Firewire disks and 63 on (E)IDE disks. It does not matter which types of partitions are used for Linux. Primary and logical partitions both function normally.

Creating a Partition

To create a partition from scratch select Hard Disks and then a hard disk with free space. The actual modification can be done in the Partitions tab:

Select Add partition. If several hard disks are connected, a selection dialog appears in which to select a hard disk for the new partition.

Specify the partition type (primary or extended). Create up to four primary partitions or up to three primary partitions and one extended partition. Within the extended partition, create several logical partitions (see Section “Partition Types”).

Select the file system to use, and a mount point. YaST suggests a mount point for each partition created. To use a different mount method, like mount by label, select Fstab Options.

Specify additional file system options if your setup requires them. This is necessary, for example, if you need persistent device names. For details on the available options, refer to Section “Editing a Partition”.

Click OK+Apply to apply your partitioning setup and leave the partitioning module.

If you created the partition during installation, you are returned to the installation overview screen.

Editing a Partition

When you create a new partition or modify an existing partition, set various parameters. For new partitions, suitable parameters are set by YaST and usually do not require any modification. To edit your partition setup manually, proceed as follows:

Select the partition.

Click Edit to edit the partition and set the parameters:

File System ID

Even if you do not want to format the partition at this stage, assign it a file system ID to ensure that the partition is registered correctly. Possible values include Linux, Linux swap, Linux LVM, and Linux RAID.

File System

Change the file system or format the partition here. Changing the file system or reformatting partitions irreversibly deletes all data from the partition.

Swap is a special format that allows the partition to be used as virtual memory. Create a swap partition of at least 256 MB. However, if you use up your swap space, consider adding more memory to your system instead of adding more swap space.

Ext4 is now the default file system for the Linux partitions. ReiserFS, JFS, XFS, Ext4 and Ext3 are journaling file systems. These file systems are able to restore the system very quickly after a system crash, utilizing write processes logged during the operation. Furthermore, ReiserFS is very fast in handling multiple small files. Ext2 is not a journaling file system. However, it is adequate for smaller partitions, because it does not require much disk space for management.

Encrypt File System

If you activate the encryption, all data is written to the hard disk in encrypted form. This increases the security of sensitive data, but reduces the system speed, as the encryption takes some time to process. More information about the encryption of file systems is provided in “Encrypting Partitions and Files” (↑Security Guide).

Fstab Options

Specify various parameters contained in the global file system administration file (/etc/fstab). The default settings should suffice for most setups. You can, for example, change the file system identification from the device name to a volume label. In the volume label, use all characters except / and space.

To get persistent devices names, use the mount option Device ID, UUID or LABEL. In openSUSE, persistent device names are enabled by default.

When using the mount option LABEL to mount a partition, define an appropriate label for the selected partition. For example, you could use the partition label HOME for a partition intended to mount to /home.

If you intend to use quotas on the file system, use the mount option Enable Quota Support. This must be done before you can define quotas for users in the YaST User Management module. For further information on how to configure user quota, refer to Section “Managing Quotas”.

Mount Point

Specify the directory where the partition should be mounted in the file system tree. Select from the offered YaST proposals or enter any other name.

Select OK+Apply to activate the partition.

Resize Filesystems

To resize an existing file system, select the partition and use Resize. Note that it is not possible to resize partitions while mounted. To resize partitions, unmount the related partition before running the partitioner.

More Partitioning Tips

The following section comprises a few hints and tips on partitioning that should help you in taking the right decisions while setting up your system.

Cylinder Numbers

Note, that different partitioning tools may start counting the cylinders of a partition with 0 or with 1. When calculating the number of cylinders, you should always use the difference between the last and the first cylinder number and add one.

Using swap

Swap is used to extend the available physical memory. This makes it possible to use more memory than physical ram available. The memory management system of kernels before 2.4.10 needed swap as a safety measure. Then, if you did not have twice the size of your ram in swap, the performance of the system suffered. These limitations no longer exist.

Linux uses a page called “Least Recently Used” (LRU) to select pages that might be moved from memory to disk. Therefore, running applications have more memory available and caching works more smoothly.

If an application tries to allocate the maximum allowed memory, problems with swap can arise. There are three major cases to look at:

System with no swap

The application gets the maximum allowed memory. All caches are freed, and thus all other running applications are slowed. After a few minutes, the kernel's out-of-memory kill mechanism activates and kills the process.

System with medіum sized swap (128 MB–512 MB)

At first, the system slows like a system without swap. After all physical RAM has been allocated, swap space is used as well. At this point, the system becomes very slow and it becomes impossible to run commands from remote. Depending on the speed of the hard disks that run the swap space, the system stays in this condition for about 10 to 15 minutes until the out-of-memory kill mechanism resolves the issue. Note that you will need a certain amount of swap if the computer needs to perform a “suspend to disk”. In that case, the swap size should be large enough to contain the necessary data from memory (512 MB–1GB).

System with lots of swap (several GB)

It is better to not have an application that swaps in an uncontrolled manner. If you do have this problem, the system will need many hours to recover. In the process, it is likely that other processes get timeouts and faults, leaving the system in an undefined state, even if the faulty process is killed. In this case, reboot the machine hard and try to get it running again. Lots of swap is only useful if you have an application that relies on this feature. Such applications (like databases or graphics manipulation programs) often have an option to directly use hard disk space for their needs. It is advisable to use this option instead of using lots of swap space.

If your system is not out of control, but needs more swap after some time, it is possible to extend the swap space online. If you prepared a partition for swap space, just add this partition with YaST. If you do not have a partition available, you may also just use a swap file to extend the swap. Swap files are generally slower than partitions, but compared to physical RAM, the difference is negligible.

Procedure 2.1. Adding a Swap File Manually

To add a swap file in the running system, proceed as follows:

Create an empty file in your system. For example, if you want to add a swap file with 128 MB swap at /var/lib/swap/swapfile, use the commands:

mkdir -p /var/lib/swap
dd if=/dev/zero of=/var/lib/swap/swapfile bs=1M count=128

Initialize this swap file with the command

mkswap /var/lib/swap/swapfile

Activate the swap with the command

swapon /var/lib/swap/swapfile

To disable this swap file, use the command

swapoff /var/lib/swap/swapfile

Check the current available swap spaces with the command

cat /proc/swaps

Note, that at this point this is only temporary swap space. After the next reboot, it is no longer utilized.

To enable this swap file permanently, add the following line to /etc/fstab:

/var/lib/swap/swapfile swap swap defaults 0 0

Partitioning and LVM

From the expert partitioner, access the LVM configuration with Volume Management. However, if a working LVM configuration already exists on your system, it is automatically activated upon entering the initial LVM configuration of a session. In this case, all disks containing a partition (belonging to an activated volume group) cannot be repartitioned. The Linux kernel cannot reread the modified partition table of a hard disk when any partition on this disk is in use. However, if you already have a functioning LVM configuration on your system, physical repartitioning should not be necessary. Instead, change the configuration of the logical volumes.

At the beginning of the physical volumes (PVs), information about the volume is written to the partition. To reuse such a partition for other non-LVM purposes, it is advisable to delete the beginning of this volume. For example, in the VG system and PV /dev/sda2, do this with the command dd if=/dev/zero of=/dev/sda2 bs=512 count=1.

File System for Booting

The file system used for booting (the root file system or /boot) must not be stored on an LVM logical volume. Instead, store it on a normal physical partition.

For more details about LVM, see the Storage Administration Guide.

LVM Configuration

This section briefly describes the principles behind the Logical Volume Manager (LVM) and its multipurpose features. In Section “LVM Configuration with YaST”, learn how to set up LVM with YaST.

Warning

Using LVM might be associated with increased risk such as data loss. Risks also include application crashes, power failures, and faulty commands. Save your data before implementing LVM or reconfiguring volumes. Never work without a backup.

The Logical Volume Manager

The LVM enables flexible distribution of hard disk space over several file systems. It was developed because sometimes the need to change the segmenting of hard disk space arises only after the initial partitioning has already been done. Because it is difficult to modify partitions on a running system, LVM provides a virtual pool (volume group, VG for short) of memory space from which logical volumes (LVs) can be created as needed. The operating system accesses these LVs instead of the physical partitions. Volume groups can span more than only one disk so that several disks or parts of them may constitute one single VG. This way, LVM provides a kind of abstraction from the physical disk space that allows its segmentation to be changed in a much easier and safer way than with physical repartitioning. Background information regarding physical partitioning can be found in Section “Partition Types” and Section “Using the YaST Partitioner”.

Figure 2.2. Physical Partitioning versus LVM

Figure 2.2, “Physical Partitioning versus LVM” compares physical partitioning (left) with LVM segmentation (right). On the left side, one single disk has been divided into three physical partitions (PART), each with a mount point (MP) assigned so that the operating system can gain access. On the right side, two disks have been divided into two and three physical partitions each. Two LVM volume groups (VG 1 and VG 2) have been defined. VG 1 contains two partitions from DISK 1 and one from DISK 2. VG 2 contains the remaining two partitions from DISK 2. In LVM, the physical disk partitions that are incorporated in a volume group are called physical volumes (PVs). Within the volume groups, four LVs (LV 1 through LV 4) have been defined, which can be used by the operating system via the associated mount points. The border between different LVs need not be aligned with any partition border. See the border between LV 1 and LV 2 in this example.

LVM features:

Several hard disks or partitions can be combined in a large logical volume.

Provided the configuration is suitable, an LV (such as /usr) can be enlarged if free space is exhausted.

With LVM, it is possible to add hard disks or LVs in a running system. However, this requires hot-swappable hardware.

It is possible to activate a "striping mode" that distributes the data stream of a LV over several PVs. If these PVs reside on different disks, the read and write performance is enhanced, as with RAID 0.

The snapshot feature enables consistent backups (especially for servers) in the running system.

With these features, LVM is ready for heavily used home PCs or small servers. LVM is well-suited for the user with a growing data stock (as in the case of databases, music archives, or user directories). This would allow file systems that are larger than the physical hard disk. Another advantage of LVM is that up to 256 LVs can be added. However, working with LVM is different from working with conventional partitions. Instructions and further information about configuring LVM is available in the official LVM HOWTO at http://tldp.org/HOWTO/LVM-HOWTO/.

Starting from kernel version 2.6, LVM version 2 is available, which is backward-compatible with the previous LVM and enables the continued management of old volume groups. When creating new volume groups, decide whether to use the new format or the backward-compatible version. LVM 2 does not require any kernel patches. It makes use of the device mapper integrated in kernel 2.6. This kernel only supports LVM version 2. Therefore, when talking about LVM, this section always refers to LVM version 2.

LVM Configuration with YaST

The YaST LVM configuration can be reached from the YaST Expert Partitioner (see Section “Using the YaST Partitioner”) below Volume Management. The Expert Partitioner allows you to edit and delete existing partitions and also create new ones that need to be used with LVM. The first task is to create PVs that provide space to a volume group:

Select a hard disk from Hard Disks.

Change to the Partitions tab.

Click Add and enter the desired size of the PV on this disk.

Use Do not format partition and change the File System ID to 0x8E Linux LVM. Do not mount this partition.

Repeat this procedure until you have defined all the desired physical volumes on the available disks.

Creating Volume Groups

If no volume group exists on your system, you must add one (see Figure 2.3, “Creating a Volume Group”). It is possible to create additional groups by clicking on Volume Management in the System View menu, and then on Add+Volume Group. One single volume group is usually sufficient.

Enter a name for the VG, e.g. system.

Select the desired Physical Extend Size. This value defines the size of a physical block in the volume group. All the disk space in a volume group is handled in blocks of this size.

Logical Volumes and Block Sizes

The possible size of an LV depends on the block size used in the volume group. The default is 4 MB and allows for a maximum size of 256 GB for physical and LVs. The physical size should be increased, for example, to 8, 16, or 32 MB, if you need LVs larger than 256 GB.

Add the prepared PVs to the VG by selecting the device and clicking on Add. Selecting several devices is possible by holding Ctrl while selecting the devices.

Select Finish to make the VG available to further configuration steps.

Figure 2.3. Creating a Volume Group

Configuring Logical Volumes

After the volume group has been filled with PVs, define the LVs the operating system should use in the next dialog. Choose the current volume group and change to the Logical Volumes tab. Add, Edit, Resize, and Delete LVs as needed until all space in the volume group has been exhausted. Assign at least one LV to each volume group.

Figure 2.4. Logical Volume Management

Click Add and go through the wizard-like popup that opens:

Enter the name of the LV. For a partition that should be mounted to /home, a self-explanatory name like HOME could be used.

Select the size and the number of stripes of the LV. If you have only one PV, selecting more than one stripe is not useful.

Choose the filesystem to use on the LV as well as the mount point.

By using stripes it is possible to distribute the data stream in the LV among several PVs (striping). If these PVs reside on different hard disks, this generally results in a better read and write performance (similar to RAID 0). However, a striping LV with n stripes can only be created correctly if the hard disk space required by the LV can be distributed evenly to n PVs. If, for example, only two PVs are available, a LV with three stripes is impossible.

Striping

YaST cannot, at this point, verify the correctness of your entries concerning striping. Any mistake made here is apparent only later when the LVM is implemented on disk.

If you have already configured LVM on your system, the existing logical volumes can also be used. Before continuing, assign appropriate mount points to these LVs. With Next, return to the YaST Expert Partitioner and finish your work there.

Soft RAID Configuration

The purpose of RAID (redundant array of independent disks) is to combine several hard disk partitions into one large virtual hard disk to optimize performance and/or data security. Most RAID controllers use the SCSI protocol because it can address a larger number of hard disks in a more effective way than the IDE protocol. It is also more suitable for the parallel command processing. There are some RAID controllers that support IDE or SATA hard disks. Soft RAID provides the advantages of RAID systems without the additional cost of hardware RAID controllers. However, this requires some CPU time and has memory requirements that make it unsuitable for high performance computers.

With openSUSE® , you can combine several hard disks into one soft RAID system. RAID implies several strategies for combining several hard disks in a RAID system, each with different goals, advantages, and characteristics. These variations are commonly known as RAID levels.

Common RAID levels are:

RAID 0

This level improves the performance of your data access by spreading out blocks of each file across multiple disk drives. Actually, this is not really a RAID, because it does not provide data backup, but the name RAID 0 for this type of system is commonly used. With RAID 0, two or more hard disks are pooled together. Performance is enhanced, but the RAID system is destroyed and your data lost if even one hard disk fails.

RAID 1

This level provides adequate security for your data, because the data is copied to another hard disk 1:1. This is known as hard disk mirroring. If one disk is destroyed, a copy of its contents is available on the other one. All disks but one could be damaged without endangering your data. However, if the damage is not detected, the damaged data can be mirrored to the undamaged disk. This could result in the same loss of data. The writing performance suffers in the copying process compared to using single disk access (10 to 20 % slower), but read access is significantly faster in comparison to any one of the normal physical hard disks. The reason is that the duplicate data can be parallel-scanned. Generally it can be said that Level 1 provides nearly twice the read transfer rate of single disks and almost the same write transfer rate as single disks.

RAID 2 and RAID 3

These are not typical RAID implementations. Level 2 stripes data at the bit level rather than the block level. Level 3 provides byte-level striping with a dedicated parity disk, and cannot service simultaneous multiple requests. These levels are rarely used.

RAID 4

Level 4 provides block-level striping just like Level 0 combined with a dedicated parity disk. In the case of data disk failure, the parity data is used to create a replacement disk. However, the parallel disk may create a bottleneck for write access.

RAID 5

RAID 5 is an optimized compromise between Level 0 and Level 1, in terms of performance and redundancy. The hard disk space equals the number of disks used minus one. The data is distributed over the hard disks as with RAID 0. Parity blocks, created on one of the partitions, exist for security reasons. They are linked to each other with XOR, enabling the contents to be reconstructed by the corresponding parity block in case of system failure. With RAID 5, no more than one hard disk can fail at the same time. If one hard disk fails, it must be replaced as soon as possible to avoid the risk of losing data.

Other RAID Levels

Several other RAID levels have been developed (RAIDn, RAID 10, RAID 0+1, RAID 30, RAID 50, etc.), some of them being proprietary implementations created by hardware vendors. These levels are not very common and therefore are not explained here.

Soft RAID Configuration with YaST

The YaST RAID configuration can be reached from the YaST Expert Partitioner, described in Section “Using the YaST Partitioner”. This partitioning tool enables you to edit and delete existing partitions and create new ones to be used with soft RAID:

Select a hard disk from Hard Disks.

Change to the Partitions tab.

Click Add and enter the desired size of the raid partition on this disk.

Use Do not Format the Partition and change the File System ID to 0xFD Linux RAID. Do not mount this partition.

Repeat this procedure until you have defined all the desired physical volumes on the available disks.

For RAID 0 and RAID 1, at least two partitions are needed—for RAID 1, usually exactly two and no more. If RAID 5 is used, at least three partitions are required. It is recommended to utilize partitions of the same size only. The RAID partitions should be located on different hard disks to decrease the risk of losing data if one is defective (RAID 1 and 5) and to optimize the performance of RAID 0. After creating all the partitions to use with RAID, click RAID+Add RAID to start the RAID configuration.

In the next dialog, choose between RAID levels 0, 1, 5, 6 and 10. Then, select all partitions with either the “Linux RAID” or “Linux native” type that should be used by the RAID system. No swap or DOS partitions are shown.

Figure 2.5. RAID Partitions

To add a previously unassigned partition to the selected RAID volume, first click the partition then Add. Assign all partitions reserved for RAID. Otherwise, the space on the partition remains unused. After assigning all partitions, click Next to select the available RAID Options.

In this last step, set the file system to use as well as encryption and the mount point for the RAID volume. After completing the configuration with Finish, see the /dev/md0 device and others indicated with RAID in the expert partitioner.

Troubleshooting

Check the file /proc/mdstat to find out whether a RAID partition has been damaged. In the event of a system failure, shut down your Linux system and replace the defective hard disk with a new one partitioned the same way. Then restart your system and enter the command mdadm /dev/mdX --add /dev/sdX. Replace 'X' with your particular device identifiers. This integrates the hard disk automatically into the RAID system and fully reconstructs it.

Note that although you can access all data during the rebuild, you may encounter some performance issues until the RAID has been fully rebuilt.

For More Information

Configuration instructions and more details for soft RAID can be found in the HOWTOs at:

/usr/share/doc/packages/mdadm/Software-RAID.HOWTO.html

http://en.tldp.org/HOWTO/Software-RAID-HOWTO.html

Linux RAID mailing lists are available, such as http://marc.theaimsgroup.com/?l=linux-raid.

Part II. Managing and Updating Software

Chapter 3. Installing or Removing Software

Abstract

In YaST's software management tool search for software components you want to add or remove. YaST resolves all dependencies for you. Add additional software repositories to your setup to install packages not shipped with the installation media and let YaST manage them. Keep your system up-to-date by managing software updates with openSUSE Updater.

Change the software collection of your system using YaST. This YaST module is available in three toolkit flavors: Qt, GTK+, and ncurses; Qt and GTK+ flavors are described here, see Chapter 10, YaST in Text Mode for details on the ncurses YaST.

Changing the toolkit flavor

By default, YaST is started with the toolkit matching your desktop (GTK+ under GNOME, Qt under KDE). Change the variable WANTED_GUI in /etc/sysconfig/yast2 to either qt or gtk to alter this default setting system-wide.

You may also use the options --gtk or --qt when starting yast from the command line to overwrite the default settings.

Definition of Terms

Repository

A local or remote directory containing packages, plus additional information about these packages (package meta-data).

(Repository) Alias

A short name for a repository used by various zypper commands. The alias can be chosen by the user when adding a repository and must be unique.

Product

Represents a whole product, for example openSUSE.

Pattern

A pattern is an installable list of packages needed for a special purpose. Examples are Base System, providing the openSUSE basic system, or GNOME Base System, containing all packages needed to run the GNOME Desktop environment.

Package

A package is a compressed file in rpm format that contains the files for a particular program.

Patch

A patch consists of one or more packages—either full packages or patchrpm or deltarpm packages— and may also introduce dependencies to packages that are not installed yet.

Resolvable

An generic term for product, pattern, package or patch. The most commonly used type of resolvable is a package or a patch.

patchrpm

A patchrpm consists only of files that have been updated since it was first released for openSUSE 11.2. Its download size is usually considerably smaller than the size of a package.

deltarpm

A deltarpm consists only of the binary diff between two defined versions of a package, and therefore has the smallest download size. Before being installed, the rpm package must be rebuilt on the local machine.

Using the Qt Interface

The YaST Qt interface is started by default when using the desktops KDE, icewm, and others. It is also used when invoking YaST from a remote terminal. Start the software manager from the YaST Control Center by Software+Software Manager

Searching Packages or Patterns

The YaST software manager can install packages or patterns from all currently-enabled repositories. It offers different views and filters to make it easier to find the software you are searching for. Change the view by clicking View and selecting a view listed below. The selected view opens in a new tab.

Search

The package search interface is the default view of the software manager. Enter a search term and press Enter. Refine your search by specifying where to Search in and by changing the Search Mode.

Patterns

Lists all patterns available for installation on your system.

Package Groups

Lists all packages sorted by groups such as Graphics, Programming, or Security.

RPM Groups

Lists all packages sorted by groups and subgroups, for example Productivity+Graphics+Viewers.

Repository

Filter to list packages by repository. In order to select more than one repository, hold the Ctrl key while clicking on repository names. The “pseudo repository” @System lists all packages currently installed.

Languages

Filter to list all packages needed to add a new system language.

Finding Packages Not Belonging to an Active Repository

To list all packages that do not belong to an active repository, choose View+Patterns+System and then choose Secondary Filter+Unmaintained Packages. This is for example useful if you have deleted a repository and would like to make sure no packages from that repository remain installed.

Installing and Removing Packages or Patterns

Search for packages as described in Section “Searching Packages or Patterns”.

The packages found are listed in the right pane. Select a package for installation or removal by right-clicking it and choosing Install or Delete. If the relevant option is not available, check the package status indicated by the symbol in front of the package name—hit Shift+F1 for help.

Applying an Action to All Packages Listed

To apply an action to all packages listed in the right pane, choose an action from Package+All in This List.

To install a pattern, right-click the pattern name and choose Install. It is not possible to delete patterns.

If your choice results in a dependency conflict that cannot be automatically solved, you need to manually solve this conflict as described in Section “Checking Software Dependencies”.

In order to select more packages, repeat the steps mentioned above. Once you are finished click Accept to start the installation.

Reviewing the Package Selection

YaST maintains a list with all actions that will be carried out when starting the installation. To review this list, choose View+Instalation Summary. By default, all packages that will change status, are listed. Use the check boxes under Show Packages with Status to filter these list. Hit Shift+F1 for details on the status flags.

In order to revert the status for a package, right-click it and select Keep if the package was scheduled to be deleted or updated, or Do not install if it was scheduled for installation. To abandon all changes and close the software manager, click Cancel and Abandon

Certain packages are dependent on other packages, such as shared libraries. YaST automatically resolves these dependencies. On the other hand, some packages cannot co-exist with others on the system. In this cases, a list of packages that have automatically been chosen for installation, update or removal is presented. Accept them by clicking continue.

Once all selected packages are installed or removed, the YaST package manager automatically terminates.

Installing Sources

Installing source packages with the YaST software manager is not possible at the moment. Use the command line tool zypper for this purpose. For more information, see Section “Installing Source Packages”.

Updating packages

To update all packages from a certain repository, choose the repository as described in Section “Searching Packages or Patterns” and then choose Package+All in This List+Update if Newer Version Available.

To update all installed packages, choose Package+All Packages+Update if Newer Version Available

Choosing Update Unconditionally instead of Update if Newer Version Available will “update” all selected packages to the version from the repository with the highest priority, even if this means actually downgrading the package. This option is for example useful to ensure that the package selection will originate from a certain repository.

Checking Software Dependencies

Most packages are dependent on other packages. If a package, for example, uses a shared library, it will be dependent on the package providing this library. On the other hand some packages cannot coexist with each other (you can for example only install one mail transfer agents, sendmail or postfix), causing a conflict. When installing or removing software, the software manager makes sure no dependencies or conflicts remain unresolved, hence ensuring system integrity.

In case there is just one simple solution to resolve a dependency or a conflict, it is resolved automatically. Multiple solutions always cause a conflict which needs to be resolved automatically. If solving a conflict involves a vendor or architecture change, it also needs to be solve manually. Once you start the installation by clicking Accept, you will get an overview of all actions triggered by the automatic resolver which you need to confirm.

By default, dependencies are automatically checked. A check is performed every time you change a package status (for example by marking a package for installation or removal). This is generally useful, but can become cumbersome when manually resolving a dependency conflict. To disable it, uncheck Dependencies+Autocheck. Manually perform a dependency check with Dependencies+Check Now. A consistency check is always performed when you confirm your selection with Accept.

To review a package's dependencies, right-click it and choose Show Solver Information. A map showing the dependencies opens. Packages that are already installed are displayed in a green frame.

Manually Solving Package Conflicts

Unless you are very experienced, follow the suggestions YaST makes when handling package conflicts, otherwise you may not be able to resolve them. Keep in mind that every change you make, potentially triggers other conflicts, so you can easily end up with a steadily increasing number of conflicts. In case this happens, Cancel the software manger, Abandon all your changes and start again.

Figure 3.1. Conflict Management of the Package Manager

Using the GTK+ Interface

The YaST GTK+ interface is started by default when using the desktops GNOME and XFCE. Start the software manager from the YaST Control Center by Software+Software Manager

Searching Packages or Patterns

The easiest way to find a package is to use the search field in the upper right corner of the software manager. Enter a search term and press Enter. By default it will search package names and summaries. Press the search item to change this filter and search the file lists, for example. The software manager also offers different views and filters for displaying package lists. These are available from the pull-down menu in the upper left corner:

Groups

The default view lists all packages sorted by groups such as Graphics, Programming, or Security. To lists all packages sorted by groups and subgroups, for example Productivity+Graphics+Viewers, click Detailed.

Patterns

Lists all patterns available for installation on your system.

Languages

Filter to list all packages needed to add a new system language.

Repository

Filter to list packages by repository. In order to select more than one repository, hold the Ctrl key while clicking on repository names. The “pseudo repository” @System lists all packages currently installed.

Installing and Removing Packages or Patterns

Search for packages as described in Section “Searching Packages or Patterns”.

The packages found are listed in the right pane. Packages that can be selected for installation are listed under the tab Install. Packages available for upgrade or removal are listed under Upgrade or Remove, respectively. Click on the checkbox in front of the package to mark it for installation, removal, or upgrade.

Applying an Action to All Packages Listed

To apply an action to all packages listed in the right pane, right-click a package, choose Select All, right-click again and choose an action.

To install a pattern, choose a pattern by clicking it's name and then click Install All in the bottom right corner.

If your choice results in a dependency conflict that cannot be automatically resolved, you need to manually solve this conflict as described in Section “Checking Software Dependencies”.

In order to select more packages, repeat the steps mentioned above. Once you are finished, click Apply to review all actions and start the installation.

YaST maintains a list with all actions that will be carried out when starting the installation. All packages that will change status are listed. Accept the changes and start the installation by clicking Sure?. To undo changes, right-click a package and choose Undo. To abandon all changes and close the software manager, click Cancel and Quit.

Once all selected packages are installed or removed, the YaST package manager automatically terminates.

Installing Sources

Installing source packages with the YaST software manager is not possible at the moment. Use the command line tool zypper for this purpose. For more information, see Section “Installing Source Packages”.

Checking Software Dependencies

Most packages are dependent on other packages. If a package, for example, uses a shared library, it will be dependent on the package providing this library. On the other hand, some packages cannot coexist with each other (you can for example only install one mail transfer agents, sendmail or postfix), causing a conflict. When installing or removing software, the software manager makes sure no dependencies or conflicts remain unresolved, hence ensuring system integrity.

In case there is just one simple solution to resolve a dependency or a conflict, it is resolved automatically. Multiple solutions always cause a conflict which needs to be resolved automatically. If solving a conflict involves a vendor or architecture change, it also needs to be solve manually. Once you start the installation by clicking Accept, you will get an overview of all actions triggered by the automatic resolver which you need to confirm.

Manually Solving Package Conflicts

Unless you are very experienced, follow the suggestions YaST makes when handling package conflicts, otherwise you may not be able to resolve them. Keep in mind that every change you make, potentially triggers other conflicts, so you can easily end up with a steadily increasing number of conflicts. In case this happens, click Cancel and Quit the software manger. Launch it again to start again.

Figure 3.2. Conflict Management of the Package Manager

Managing Software Repositories and Services

Add additional software repositories to your system to install third-party software. By default, the product repositories such as openSUSE-DVD 11.2 and a matching update repository are automatically configured during the installation. Depending on the initially selected product, a separate language add-on repository with translations, dictionaries, etc. might also be configured.

Here also manage subscriptions to so-called Services. A Service in this context is a Repository Index Service (RIS) that can offer one or more software repositories. Such a Service can be changed dynamically by its administrator or vendor.

Trusting External Software Sources

Before adding external software repositories to your list of repositories, make sure this repository can be trusted. openSUSE is not responsible for any potential problems arising from software installed from third-party software repositories.

Adding Software Repositories

To add product repositories either click Software Repositories directly in the Software pane of the YaST control center, or Configuration+Repositories... in the Software Management module. Proceed as follows:

Click Add.

Select the repository type. Normally you will want to stick with the default Specify URL.... For add-on CDs or DVDs choose the relevant option. Each repository provides files describing content of the repository. Check Download repository description files to download these files now. If the option is unchecked, YaST will automatically download the files when it needs them later. Click Next.

Either provide the necessary data or insert the medium. Confirm with Continue. It will take some time until YaST has downloaded and parsed the metadata of the repository. Once done you can install software from this repository as described in Section “Using the Qt Interface” resp. Section “Using the GTK+ Interface”.

If you want to add a repository of the openSUSE® Build Service, such as the Mozilla repository (containing packages with the most recent versions of Firefox and Thunderbird), use the Community Repositories configuration dialog of YaST:

Start the YaST module Software Repositories.

Click Add.

Choose Community Repositories and proceed with Next.

From the preconfigured list of repositories choose the ones you would like to add by ticking the respective check boxes. The Mozilla repository, for example, is listed as openSUSE BuildService - Mozilla.

Confirm with OK.

Accept to Import the GnuPG key. You need to import a key for each repository you have chosen.

The new software repositories are now listed in the Configured Software Repositories overview. Click OK to leave the software repositories configuration.

Managing Repository Properties

The Configured Software Repositories overview of the Software Repositories lets you change the following properties of the repositories:

Status

The repository status can either be Enabled or disabled. You can only install packages from repositories that are enabled. Disable a repository to turn it off temporarily. In order to completely remove a repository, Delete it rather than disable it.

Tip

Double-clicking on a repository name toggles its status.

Refresh

When refreshing a repository, its content description (package names, versions, etc.) is downloaded to a local cache that is used by YaST. It is sufficient to do this once for static repositories such as CDs or DVDs, whereas repositories whose content changes often should be refreshed frequently. The easiest way to keep a repositories cache up-to-date is to Automatically Refresh it. You can also do a manual refresh by clicking on the Refresh button.

Keep Downloaded Packages

Packages from remote repositories are downloaded before being installed. By default, they are deleted upon a successful installation. Activating Keep Downloaded Packages prevents the deletion of downloaded packages. The download location is configured in /etc/zypp/zypp.conf, by default it is /var/cache/zypp/packages.

Priority

The Priority of a repository is a value between 0 and 200, where 0 is the highest priority. If a package is available in more than one repository, then the repository with the highest priority takes precedence. This is useful if you want to give a local repository (for example, a DVD) a higher priority to avoid downloading packages unnecessarily from the Internet, although they have the same or a higher version number.

Priority vs. Version

The repository with the highest priority takes precedence in any case, even when this means to not install the package with the highest version number. Therefore make sure that the update repository always has the highest priority (20 by default), otherwise you might install an outdated version that will not get updated until the next online update.

On the other hand, if you add repositories providing new versions for programs shipped with openSUSE (for example a repository with the latest KDE or GNOME version), make sure it has got a higher priority than the standard repositories, otherwise packages from these repositories will not be installed by default.

Name and URL

To change a repository name or it's URL, select it from the list with a single click and then click Edit.

Managing Repository Keys

To ensure their integrity, software repositories can be signed with the GPG Key of the repository maintainer. Whenever you add a new repository, YaST offers the ability to import its key. Verify it as any other GPG key and make sure that it does not change. If you detect a key change, something could be wrong with the repository and you should disable it as an installation source until you know the cause of the key change.

To manage all imported keys, click GPG Keys... in the Software Repositories module. Select an entry with the mouse to see the key properties. Add new keys, Edit or Delete existing ones.

Chapter 4. YaST Online Update

openSUSE offers a continuous stream of software security updates for your product. By default openSUSE Updater is used to keep your system up-to-date. Refer to “Keeping the System Up-to-date” (Chapter “Installing, Removing and Updating Software”, ↑Start-Up) for further information on openSUSE Updater. This chapter covers the alternative tool for updating software packages: YaST Online Update.

The current patches for openSUSE® are available from an update software repository, which is automatically configured during the installation. Conversely, you can manually add an update repository from a source you trust. To add or remove repositories, start the Repository Manager with Software+Software Repositories in YaST. Learn more about the Repository Manager in Section “Managing Software Repositories and Services”.

openSUSE provides updates with different relevance levels. Security updates fix severe security hazards and should definitely be installed. Recommended updates fix issues that could compromise your computer, whereas Optional updates fix non-security relevant issues or provide enhancements.

Procedure 4.1. Installing Patches with YaST Online Update

Run Software+Online Update in YaST

All new patches (except the optional ones) that are currently available for your system are already marked for installation. Click Accept or Apply to automatically install them.

Confirm with Finish after the installation has completed. Your system is now up-to-date.

Disabling deltarpms

By default updates are downloaded as deltarpms. Since rebuilding rpm packages from deltarpms is a memory and CPU time consuming task, certain setups or hardware configurations might require you to disable the usage of deltarpms for performance sake. To disable the use of deltarpms edit the file /etc/zypp/zypp.conf and set download.use_deltarpm to false.

Installing Patches Manually Using the Qt Interface

The Online Update window consists of four sections. The list of all patches available is on the left. Find the description of the selected patch displayed below the list of patches. The right column lists the packages included in the selected patch (a patch can consist of several packages) and below, a detailed description of the selected package.

Figure 4.1. YaST Online Update

The patch display lists the available patches for openSUSE. The patches are sorted by security relevance (security, recommended, and optional). There are three different views on patches. Use Show Patch Category to toggle the views:

Needed Patches (default view)

Non-installed patches that apply to packages installed on your system.

Unneeded Patches

Patches that either apply to packages not installed on your system, or patches that have requirements which have already have been fulfilled (because the relevant packages have already been updated from another source).

All Patches

All patches available for openSUSE.

A list entry consists of a symbol and the patch name. For a list of possible symbols, press Shift+F1. Actions required by Security and Recommended patches are automatically preset. These actions are Autoinstall, Autoupdate and Autodelete. Actions for Optional patches are not preset—right-click on a patch and choose an action from the list.

If you install an up-to-date package from a repository other than the update repository, the requirements of a patch for this package may be fulfilled with this installation. In this case a check mark is displayed in front of the patch summary. The patch will be visible in the list until you mark it for installation. This will in fact not install the patch (because the package already is up-to-date), but mark the patch as having been installed.

Most patches include updates for several packages. If you want to change actions for single packages, right-click on a package in the package window and choose an action. Once you have marked all patches and packages as desired, proceed with Accept.

Installing Patches Manually Using the GTK Interface

The Online Update window consists of two main sections. The left pane lists all patches and provides different filters for the patch list. See the right pane for a list of changes that will carried out once you Apply them.

Figure 4.2. YaST Online Update

Patch List Filters

Available

Non-installed patches that apply to packages installed on your system.

Installed

Patches that are already installed.

All

Patches that are either already installed or available.

Severity

Only show Optional, Recommended, or Security patches. By default, All patches are shown.

Repositories

This filter lets you display the patches per repository.

Packages Listing

Apply your custom filter here.

Click on a patch entry to open a row with detailed information about the patch in the bottom of the window. Here you can see a detailed patch description as well as the versions available. You can also choose to Install optional patches—security and recommended patches are already preselected for installation.

Automatic Online Update

YaST also offers the possibility to set up an automatic update. Open Software+Online Update Configuration. Check Automatic Online Update and choose whether to update Daily, Weekly, or Monthly. Some patches, such as kernel updates, require user interaction, which would cause the automatic update procedure to stop. Therefore you should check Skip Interactive Patches if you want the update procedure to proceed fully automatically. Having done so, you should run a manual Online Update from time to time in order to install patches that require interaction.

Chapter 5. Installing Packages From the Internet

Abstract

By default, it is only possible to install packages from configured and enabled repositories. Apart from the official repositories that are configured during the installation, numerous other repositories exist. The openSUSE Build Service hosts several hundred ones and a lot of third party repositories exist, too—see http://en.opensuse.org/Additional_YaST_Package_Repositories for example.

openSUSE offers two easy ways to install from these repositories without the need to first subscribe to them. The “1-Click Install” method allows you to install packages directly from a web browser, while the YaST Package Search lets you query almost all known repositories for openSUSE. You can directly install any package found by the package search module.

Trusting External Software Sources

Before installing from external software repositories, make sure it can be trusted. openSUSE is not responsible for any potential problems arising from software installed from third-party software repositories.

1-Click Install

The “1-Click Install” is available from a lot of repositories browseable by web interface. A very popular interface is the openSUSE Build Service software search. To install a package from the BuildService via “1-Click Install” proceed as follows:

Start the openSUSE Build Service software search at http://software.opensuse.org/search.

Select your system version from the drop-down menu, for example openSUSE 11.2. Search for the package you want to install, for example the OpenStreetMap editor josm.

Click Search.

From the results list select the preferred item by clicking it's 1-Click Install button.

In the Web browser's open file download dialog, select to open the file with the YaST Meta Package Handler.

The 1-click installer opens. In the Additional Software Repositories dialog you can select software repositories to subscribe to. Normally there is no need to change the default selection. By default you remain subscribed to these repositories after the installation has finished, so you will receive updates from them in the future. Uncheck Remain Subscribed to These Repositories after Installation to only use the repositories once. Click Next to proceed.

Now select the software packages that should be installed. Normally there is no need to change the default selection. Click Next to proceed.

The Proposal screen summarizes the choices you made. Click Customise to restart the configuration steps from above. Click Next and Yes to proceed with the installation.

Enter the root password to start the installation. In case a new repository was added you also need to confirm the import of the repository's GnuPG key. During the installation several progress pop-ups appear that do not need any interaction. After reading the “Installation was successful” message, click Finish.

Disabling 1-Click Install Feature

If you want to disable the 1-Click install feature, uninstall the yast2-metapackage-handler package using YaST or entering the following command as root:

rpm -e yast2-metapackage-handler

YaST Package Search

Provided you are connected to the internet, you can also search and install packages from almost all known repositories for openSUSE directly via YaST's Package Search. This module is not available by default, you need to install the package yast2-packager-webpin. This module is a YaST frontend for the Webpin package search available at http://packages.opensuse-community.org/. To install packages via the Package Search proceed as follows:

Start the Package Search from the YaST Control Center via Software+Package Search.

Search for a software package by entering it's name into the Search Expression field and clicking Search.

The search result is listed in the tab Found Packages. Click on a package name to see the repository URL, the package version number and the architecture in the Package Description pane.

Double check the Package Information

Make sure to double check whether the software is hosted on a repository you trust before you install it. Also check if the architecture complies with your system (x86_64 packages can only be installed on 64bit systems).

Mark a package for installation by clicking its checkbox. You can mark several packages at once. You can even start a new search for other packages without losing your current selection, which is always available on the All Selected Packages. Once you have finished the package selection, proceed with Next.

In the Additional Software Repositories dialog you can select software repositories to subscribe to. Normally there is no need to change the default selection. By default, you remain subscribed to these repositories after the installation has finished, so you will receive updates from them in the future. Uncheck Remain Subscribed to These Repositories after Installation to use the repositories only once. Click Next to proceed.

Now select the software packages that should be installed. Normally there is no need to change the default selection. Click Next to proceed.

The Proposal screen summarizes the choices you made. Click Customise to restart the configuration steps from above. Click Next and Yes to proceed with the installation.

Confirm the next dialog. In case a new repository is used, you will also need to confirm the import of the repository's GnuPG key. During the installation several progress pop-ups appear that do not need any interaction. After reading the “Installation was successful” message, click Finish.

Chapter 6. Installing Add-On Products

Abstract

Add-on products are system extensions. You can install a third party add-on product or a special system extension of openSUSE (for example, a CD with support for additional languages or a CD with binary drivers). To install a new add-on, use Software+Add-On Products. You can select various types of product media, like CD, FTP, USB mass storage devices (such as USB flash drives or disks) or a local directory. You can work also directly with ISO files. To add an add-on as ISO file media, select Local ISO Image then enter the Path to ISO Image. The Repository Name is arbitrary.

Add-Ons

To install a new add-on, proceed as follows:

Click Software+Add-On Products to see an overview of installed add-on products.

Select the Add-On repository type and click Next.

Either provide the necessary data or insert the medium. Confirm with Continue. It will take some time until YaST has downloaded and parsed the metadata of the repository.

After having successfully added the add-on media, the software manager starts and you can install packages. Please refer to Chapter 3, Installing or Removing Software for details.

Binary Drivers

Some hardware needs binary-only drivers to function properly. If you have such hardware, refer to the release notes for more information about availability of binary drivers for your system. To read the release notes, open YaST and select Miscellaneous+Release Notes.

Chapter 7. Managing Software with Command Line Tools

Abstract

This chapter describes Zypper and RPM, two command line tools for managing software.

Using Zypper

Zypper is a command line package manager for installing, updating and removing packages as well as for managing repositories. It is especially useful for accomplishing remote software management tasks or managing software from shell scripts.

For more information on managing software from the command line, enter zypper help or zypper help command or see the zypper(8) manpage. Also see http://en.opensuse.org/Zypper/Usage for a complete and detailed command-reference.

General Usage

The general syntax of zypper is:

zypper [global-options] command [command-options] [arguments] ...

The components enclosed in brackets are not required. The simplest way to execute zypper is to type its name, followed by a command. For example, to apply all needed patches to the system type:

zypper patch

Additionally, you can choose from one or more global options by typing them just before the command. For example, --non-interactive means running the command without asking anything (automatically applying the default answers):

zypper --non-interactive patch

To use the options specific to a particular command, type them right after the command. For example, --auto-agree-with-licenses means applying all needed patches to the system without asking to confirm any licenses (they will automatically be accepted):

zypper patch --auto-agree-with-licenses

Some commands require one or more arguments. When using the install command, for example, you need to specify which package(s) to install:

zypper install mplayer

Some options also require an argument. The following command will list all known patterns:

zypper search -t pattern

You can combine all of the above. For example, the following command will install mplayer and amarok packages using the factory repository only, and be verbose:

zypper -v install --repo factory mplayer amarok

Most Zypper commands have a dry-run option that does a simulation of the given command. It can be used for test purposes.

zypper remove --dry-run MozillaFirefox

Installing and Removing Software with Zypper

To install or remove packages use the following commands:

zypper install package
zypper remove package

Zypper knows various ways to address packages for the install and remove commands:

by the exact package name

zypper in MozillaFirefox

by repository alias and package name

zypper in mozilla:MozillaFirefox

Where mozilla is the alias of the repository from which to install.

by package name using wildcards

The following command will install all packages that have names starting with “Moz”. Use with care, especially when removing packages.

zypper in Moz*

by capability

If you, for example, would like to install a perl module without knowing the name of the package, capabilities come in handy:

zypper in 'perl(Time::ParseDate)'

by capability and/or architecture and/or version

Together with a capability you can specify an architecture (such as i586 or x86_64) and/or a version. The version must be preceded by an operator: < (lesser than), <= (lesser than or equal), = (equal>, >= (greater than or equal), > (greater than).

zypper in 'firefox.x86_64'
zypper in 'firefox>=3.5.3'
zypper in 'firefox.x86_64>=3.5.3'

by path

You can also specify a local or remote path to a package:

zypper in /tmp/install/MozillaFirefox.rpm
zypper in http://download.opensuse.org/repositories/mozilla/SUSE_Factory/x86_64/MozillaFirefox-3.5.3-1.3.x86_64.rpm

To install and remove packages simultaneously use the +/- modifiers:

zypper install emacs -vim
zypper remove emacs +vim

To prevent the package name starting with the - being interpreted as a command option, always use it as the second argument. If this is not possible, precede it with --:

zypper install -emacs +vim       # Wrong
zypper install vim -emacs        # Correct
zypper install -- -emacs +vim    # same as above
zypper remove emacs +vim         # same as above

By default, Zypper asks for a confirmation before installing or removing a selected package, or when a problem occurs. You can override this behavior using the --non-interactive option. This option must be given before the actual command (install, remove, and patch) as in the following:

zypper --non-interactive install package_name

This option allows the use of Zypper in scripts and cron jobs.

Do not Remove Mandatory System Packages

Do not remove packages such as glibc, zypper, kernel, or similar packages. These packages are mandatory for the system and, if removed, may cause the system to become unstable or stop working altogether.

Installing Source Packages

If you want to install the corresponding source package of a package, use:

zypper source-install package_name

That command will also install the build dependencies of the specified package. If you do not want this, add the switch -D. To install only the build dependencies use -d.

zypper source-install -d package_name # source package only
    zypper source-install -D package_name # build dependencies only

Of course, this will only work if you have the repository with the source packages enabled in your repository list (it is added by default, but not enabled). See Section “Managing Repositories with Zypper” for details on repository management.

A list of all source packages available in your repositories can be obtained with:

zypper search -t srcpackage

Utilities

To verify whether all dependencies are still fulfilled and to repair missing dependencies, use:

zypper verify

In addition to dependencies that must be fulfilled, some packages “recommend” other packages. These recommended packages are only installed if actually available. In case recommended packages were made available after the recommending package has been installed (by adding additional packages), use the following command:

zypper install-new-recommends

Updating Software with Zypper

There are three different ways to update software using Zypper: by installing patches, by installing a new version of a package or by updating the entire distribution. The latter is achieved with the zypper dist-upgrade command which is discussed in Section “Upgrading the System”.

Installing Patches

To install all officially released patches applying to your system, just run:

zypper patch

In this case, all patches available in your repositories are checked for relevance and installed, if necessary. The above command is all you must enter in order to apply them when needed.

Zypper knows three different commands to query for the availability of patches:

zypper patch-check

Lists the number of needed patches (patches, that apply to your system but are not yet installed)

~ # zypper patch-check
Loading repository data...
Reading installed packages...
5 patches needed (1 security patch)

zypper list-patches

Lists all needed patches (patches, that apply to your system but are not yet installed)

~ # zypper list-updates
Loading repository data...
Reading installed packages...
S | Repository | Name                          | Current | Available  | Arch
--+------------+-------------------------------+---------+------------+-------
v | Updates    | update-test-interactive       | 0-2.35  | 0-9999.1.2 | noarch
v | Updates    | update-test-optional          | 0-2.35  | 0-9999.1.2 | noarch
v | Updates    | update-test-reboot-needed     | 0-2.35  | 0-9999.1.2 | noarch
v | Updates    | update-test-relogin-suggested | 0-2.35  | 0-9999.1.2 | noarch
v | Updates    | update-test-security          | 0-2.35  | 0-9999.1.2 | noarch

zypper patches

Lists all patches available for openSUSE, regardless of whether they are already installed or apply to your installation.

Installing Updates

If a repository contains only new packages, but does not provide patches, zypper patch does not show any effect. To update all installed packages with newer available versions, use:

zypper update

To update individual packages, specify the package with either the update or install command:

zypper update package
zypper install package

A list of all new packages available can be obtained with the command:

zypper list-updates

Differences between zypper update and zypper dist-upgrade

Choose zypper update to update packages to newer versions available for your product version while maintaining system integrity. zypper update will honor the following rules:

no vendor changes

no architecture changes

no downgrades

keep installed packages

To upgrade your installation to a new product version use zypper dist-upgrade with the required repositories (see Section “Managing Repositories with Zypper” for details). This command ensures that all packages will be installed from the repositories currently enabled. This rule is enforced, so packages might change vendor or architecture or even might get downgraded. All packages that have unfulfilled dependencies after the upgrade will be uninstalled.

Managing Repositories with Zypper

All installation or patch commands of Zypper rely on a list of known repositories. To list all repositories known to the system, use the command:

zypper repos

The result will look similar to the following output:

# | Alias                 | Name                  | Enabled | Refresh
--+-----------------------+-----------------------+---------+--------
1 | Updates               | Updates               | Yes     | Yes
2 | openSUSE 11.2-0       | openSUSE 11.2-0       | No      | No
3 | openSUSE-11.2-Debug   | openSUSE-11.2-Debug   | No      | Yes
4 | openSUSE-11.2-Non-Oss | openSUSE-11.2-Non-Oss | Yes     | Yes
5 | openSUSE-11.2-Oss     | openSUSE-11.2-Oss     | Yes     | Yes
6 | openSUSE-11.2-Source  | openSUSE-11.2-Source  | No      | Yes

When specifying repositories in various commands, an alias, URI or repository number from the zypper repos command output can be used. Note however that the numbers can change after modifying the list of repositories. The alias will never change by itself.

By default, details as the URI or the priority of the repository is not displayed. Use the following command to list all details:

Adding Repositories

To add a repository, run

zypper addrepo URI Alias

URI can either be an Internet repository, a network resource, a directory or a CD or DVD (see http://en.opensuse.org/Libzypp/URI for details). The Alias is a shorthand and unique identifier of the repository. You can freely choose it, with the only exception that is has to be unique. Zypper will issue a warning if you specify an alias that is already in use. To make working with repositories more convenient, use short and easy-to-remember aliases.

Removing Repositories

If you want to remove a repository from the list, use the command zypper removerepo together with the alias or number of the repository you want to delete. To remove the 3rd entry from the example, use the following command:

zypper removerepo 3

Modifying Repositories

Enable or disable repositories with zypper modifyrepo. You can also alter the repository's properties (such as refreshing behavior, name or priority) with this command. The following command will enable the repository name “updates”, turn on auto-refresh and set it's priority to 20:

zypper mr -er -p 20 'updates'

Modifying repositories is not limited to a single repository—you can also operate on groups:

-a: all repositories

-l: local repositories

-t: remote repositories

-m TYPE: repositories of a certain type (TYPE can be one of the following: http, https, ftp, cd, dvd, dir, file, cifs, smb, nfs, hd, iso)

To rename a repository alias, use the renamerepo command. The following example changes the alias from “Mozilla Firefox” to just “firefox”:

zypper renamerepo 'Mozilla Firefox' firefox

Querying Repositories and Packages with Zypper

Zypper offers various methods to query repositories or packages. To get lists of all products, patterns, packages or patches available, use the following commands:

zypper products
zypper patterns
zypper packages
zypper patches

To query all repositories for certain packages, use search. It works on package names, capabilities or, optionally, on package summaries and descriptions. Using the wildcards * and ? with the search term is allowed. By default, the search is not case-sensitive.

zypper se firefox       # simple search for "firefox"
zypper se *fire*        # using wildcards
zypper se -d fire       # also search in package descriptions and summaries
zypper se -u firefix    # only display packages not already installed

To search for packages which provide a special capability, use the command what-provides. If you, for example, would like to know which package provides the perl Module SVN::Core, use the following command:

zypper what-provides 'perl(SVN::Core)'

To query single packages, use info with an exact package name as an argument. It displays detailed information about a package. Use the options --requires and --recommends to also show what is required/recommended by the package:

zypper info --requires MozillaFirefox

The what-provides package is similar to rpm -q --whatprovides package, but rpm is only able to query the RPM database (that is the database of all installed packages). Zypper, on the other hand, will tell you about providers of the capability from any repository, not only those that are installed.

RPM—the Package Manager

RPM (RPM Package Manager) is used for managing software packages. Its main commands are rpm and rpmbuild. The powerful RPM database can be queried by the users, system administrators and package builders for detailed information about the installed software.

Essentially, rpm has five modes: installing, uninstalling (or updating) software packages, rebuilding the RPM database, querying RPM bases or individual RPM archives, integrity checking of packages and signing packages. rpmbuild can be used to build installable packages from pristine sources.

Installable RPM archives are packed in a special binary format. These archives consist of the program files to install and certain meta information used during the installation by rpm to configure the software package or stored in the RPM database for documentation purposes. RPM archives normally have the extension .rpm.

Software Development Packages

For a number of packages, the components needed for software development (libraries, headers, include files, etc.) have been put into separate packages. These development packages are only needed if you want to compile software yourself (for example, the most recent GNOME packages). They can be identified by the name extension -devel, such as the packages alsa-devel, gimp-devel, and kdelibs3-devel.

Verifying Package Authenticity

RPM packages have a GnuPG signature. The command rpm --checksig package-1.2.3.rpm can be used to verify the signature of an RPM package to determine whether it originates from SUSE or from another trustworthy facility. This is especially recommended for update packages from the Internet.

Managing Packages: Install, Update, and Uninstall

Normally, the installation of an RPM archive is quite simple: rpm -i package.rpm. With this command the package is installed, but only if its dependencies are fulfilled and there are no conflicts with other packages. With an error message, rpm requests those packages that need to be installed to meet dependency requirements. In the background, the RPM database ensures that no conflicts arise—a specific file can only belong to one package. By choosing different options, you can force rpm to ignore these defaults, but this is only for experts. Otherwise, you risk compromising the integrity of the system and possibly jeopardize the ability to update the system.

The options -U or --upgrade and -F or --freshen can be used to update a package (for example, rpm -F package.rpm). This command removes the files of the old version and immediately installs the new files. The difference between the two versions is that -U installs packages that previously did not exist in the system, but -F merely updates previously installed packages. When updating, rpm updates configuration files carefully using the following strategy:

If a configuration file was not changed by the system administrator, rpm installs the new version of the appropriate file. No action by the system administrator is required.

If a configuration file was changed by the system administrator before the update, rpm saves the changed file with the extension .rpmorig or .rpmsave (backup file) and installs the version from the new package (but only if the originally installed file and the newer version are different). If this is the case, compare the backup file (.rpmorig or .rpmsave) with the newly installed file and make your changes again in the new file. Afterwards, be sure to delete all .rpmorig and .rpmsave files to avoid problems with future updates.

.rpmnew files appear if the configuration file already exists and if the noreplace label was specified in the .spec file.

Following an update, .rpmsave and .rpmnew files should be removed after comparing them, so they do not obstruct future updates. The .rpmorig extension is assigned if the file has not previously been recognized by the RPM database.

Otherwise, .rpmsave is used. In other words, .rpmorig results from updating from a foreign format to RPM. .rpmsave results from updating from an older RPM to a newer RPM. .rpmnew does not disclose any information as to whether the system administrator has made any changes to the configuration file. A list of these files is available in /var/adm/rpmconfigcheck. Some configuration files (like /etc/httpd/httpd.conf) are not overwritten to allow continued operation.

The -U switch is not just an equivalent to uninstalling with the -e option and installing with the -i option. Use -U whenever possible.

To remove a package, enter rpm -e package. rpm, which only deletes the package if there are no unresolved dependencies. It is theoretically impossible to delete Tcl/Tk, for example, as long as another application requires it. Even in this case, RPM calls for assistance from the database. If such a deletion is, for whatever reason, impossible (even if no additional dependencies exist), it may be helpful to rebuild the RPM database using the option --rebuilddb.

RPM and Patches

To guarantee the operational security of a system, update packages must be installed in the system from time to time. Previously, a bug in a package could only be eliminated by replacing the entire package. Large packages with bugs in small files could easily result in this scenario. However the SUSE RPM offers a feature enabling the installation of patches in packages.

The most important considerations are demonstrated using pine as an example:

Is the patch RPM suitable for my system?

To check this, first query the installed version of the package. For pine, this can be done with

rpm -q pine
pine-4.44-188

Then check if the patch RPM is suitable for this version of pine:

rpm -qp --basedon pine-4.44-224.i586.patch.rpm
pine = 4.44-188
pine = 4.44-195
pine = 4.44-207

This patch is suitable for three different versions of pine. The installed version in the example is also listed, so the patch can be installed.

Which files are replaced by the patch?

The files affected by a patch can easily be seen in the patch RPM. The rpm parameter -P allows selection of special patch features. Display the list of files with the following command:

rpm -qpPl pine-4.44-224.i586.patch.rpm
/etc/pine.conf
/etc/pine.conf.fixed
/usr/bin/pine

or, if the patch is already installed, with the following command:

rpm -qPl pine
/etc/pine.conf
/etc/pine.conf.fixed
/usr/bin/pine

How can a patch RPM be installed in the system?

Patch RPMs are used just like normal RPMs. The only difference is that a suitable RPM must already be installed.

Which patches are already installed in the system and for which package versions?

A list of all patches installed in the system can be displayed with the command rpm -qPa. If only one patch is installed in a new system (as in this example), the list appears as follows:

rpm -qPa
pine-4.44-224

If, at a later date, you want to know which package version was originally installed, this information is also available in the RPM database. For pine, this information can be displayed with the following command:

rpm -q --basedon pine
pine = 4.44-188

More information, including information about the patch feature of RPM, is available in the man pages of rpm and rpmbuild.

Official updates for openSUSE

In order to make the download size of updates as small as possible, official updates for openSUSE are not provided as Patch RPMs, but as Delta RPM packages (see Section “Delta RPM Packages” for details).

Delta RPM Packages

Delta RPM packages contain the difference between an old and a new version of an RPM package. Applying a delta RPM onto an old RPM results in a completely new RPM. It is not necessary to have a copy of the old RPM because a delta RPM can also work with an installed RPM. The delta RPM packages are even smaller in size than patch RPMs, which is an advantage when transferring update packages over the Internet. The drawback is that update operations with delta RPMs involved consume considerably more CPU cycles than plain or patch RPMs.

The prepdeltarpm, writedeltarpm and applydeltarpm binaries are part of the delta RPM suite (package deltarpm) and help you create and apply delta RPM packages. With the following commands, create a delta RPM called new.delta.rpm. The following command assumes that old.rpm and new.rpm are present:

prepdeltarpm -s seq -i info old.rpm > old.cpio
prepdeltarpm -f new.rpm > new.cpio
xdelta delta -0 old.cpio new.cpio delta
writedeltarpm new.rpm delta info new.delta.rpm

Finally, remove the temporary working files old.cpio, new.cpio, and delta.

Using applydeltarpm, you can reconstruct the new RPM from the file system if the old package is already installed:

applydeltarpm new.delta.rpm new.rpm

To derive it from the old RPM without accessing the file system, use the -r option:

applydeltarpm -r old.rpm new.delta.rpm new.rpm

See /usr/share/doc/packages/deltarpm/README" for technical details.

RPM Queries

With the -q option rpm initiates queries, making it possible to inspect an RPM archive (by adding the option -p) and also to query the RPM database of installed packages. Several switches are available to specify the type of information required. See Table 7.1, “The Most Important RPM Query Options”.

Table 7.1. The Most Important RPM Query Options

-i

Package information

-l

File list

-f FILE

Query the package that contains the file FILE (the full path must be specified with FILE)

-s

File list with status information (implies -l)

-d

List only documentation files (implies -l)

-c

List only configuration files (implies -l)

--dump

File list with complete details (to be used with -l, -c, or -d)

--provides

List features of the package that another package can request with --requires

--requires, -R

Capabilities the package requires

--scripts

Installation scripts (preinstall, postinstall, uninstall)

For example, the command rpm -q -i wget displays the information shown in Example 7.1, “rpm -q -i wget”.

Example 7.1. rpm -q -i wget

Name        : wget                         Relocations: (not relocatable)
Version     : 1.11.4                            Vendor: openSUSE
Release     : 1.70                          Build Date: Sat 01 Aug 2009 09:49:48 CEST
Install Date: Thu 06 Aug 2009 14:53:24 CEST      Build Host: build18
Group       : Productivity/Networking/Web/Utilities   Source RPM: wget-1.11.4-1.70.src.rpm
Size        : 1525431                          License: GPL v3 or later
Signature   : RSA/8, Sat 01 Aug 2009 09:50:04 CEST, Key ID b88b2fd43dbdc284
Packager    : http://bugs.opensuse.org
URL         : http://www.gnu.org/software/wget/
Summary     : A Tool for Mirroring FTP and HTTP Servers
Description :
Wget enables you to retrieve WWW documents or FTP files from a server.
This can be done in script files or via the command line.
[...]

The option -f only works if you specify the complete filename with its full path. Provide as many filenames as desired. For example, the following command

rpm -q -f /bin/rpm /usr/bin/wget

results in:

rpm-4.4.2.3-45.5
wget-1.11.4-1.70

If only part of the filename is known, use a shell script as shown in Example 7.2, “Script to Search for Packages”. Pass the partial filename to the script shown as a parameter when running it.

Example 7.2. Script to Search for Packages

#! /bin/sh
for i in $(rpm -q -a -l | grep  $1); do
    echo "\"$i\" is in package:"
    rpm -q -f $i
    echo ""
done

The command rpm -q --changelog rpm displays a detailed list of change information about a specific package, sorted by date.

With the help of the installed RPM database, verification checks can be made. Initiate these with -V, -y or --verify. With this option, rpm shows all files in a package that have been changed since installation. rpm uses eight character symbols to give some hints about the following changes:

Table 7.2. RPM Verify Options

5

MD5 check sum

S

File size

L

Symbolic link

T

Modification time

D

Major and minor device numbers

U

Owner

G

Group

M

Mode (permissions and file type)

In the case of configuration files, the letter c is printed. For example, for changes to /etc/wgetrc (wget):

rpm -V wget
S.5....T c /etc/wgetrc

The files of the RPM database are placed in /var/lib/rpm. If the partition /usr has a size of 1 GB, this database can occupy nearly 30 MB, especially after a complete update. If the database is much larger than expected, it is useful to rebuild the database with the option --rebuilddb. Before doing this, make a backup of the old database. The cron script cron.daily makes daily copies of the database (packed with gzip) and stores them in /var/adm/backup/rpmdb. The number of copies is controlled by the variable MAX_RPMDB_BACKUPS (default: 5) in /etc/sysconfig/backup. The size of a single backup is approximately 1 MB for 1 GB in /usr.

Installing and Compiling Source Packages

All source packages carry a .src.rpm extension (source RPM).

Tip

Source packages can be copied from the installation medium to the hard disk and unpacked with YaST. They are not, however, marked as installed ([i]) in the package manager. This is because the source packages are not entered in the RPM database. Only installed operating system software is listed in the RPM database. When you “install” a source package, only the source code is added to the system.

The following directories must be available for rpm and rpmbuild in /usr/src/packages (unless you specified custom settings in a file like /etc/rpmrc):

SOURCES

for the original sources (.tar.bz2 or .tar.gz files, etc.) and for distribution-specific adjustments (mostly .diff or .patch files)

SPECS

for the .spec files, similar to a meta Makefile, which control the build process

BUILD

all the sources are unpacked, patched and compiled in this directory

RPMS

where the completed binary packages are stored

SRPMS

here are the source RPMs

When you install a source package with YaST, all the necessary components are installed in /usr/src/packages: the sources and the adjustments in SOURCES and the relevant .spec file in SPECS.

Warning

Do not experiment with system components (glibc, rpm, sysvinit, etc.), because this endangers the stability of your system.

The following example uses the wget.src.rpm package. After installing the source package, you should have files similar to those in the following list:

/usr/src/packages/SOURCES/wget-1.11.4.tar.bz2
/usr/src/packages/SOURCES/wgetrc.patch
/usr/src/packages/SPECS/wget.spec

rpmbuild -bX /usr/src/packages/SPECS/wget.spec starts the compilation. X is a wild card for various stages of the build process (see the output of --help or the RPM documentation for details). The following is merely a brief explanation:

-bp

Prepare sources in /usr/src/packages/BUILD: unpack and patch.

-bc

Do the same as -bp, but with additional compilation.

-bi

Do the same as -bp, but with additional installation of the built software. Caution: if the package does not support the BuildRoot feature, you might overwrite configuration files.

-bb

Do the same as -bi, but with the additional creation of the binary package. If the compile was successful, the binary should be in /usr/src/packages/RPMS.

-ba

Do the same as -bb, but with the additional creation of the source RPM. If the compilation was successful, the binary should be in /usr/src/packages/SRPMS.

--short-circuit

Skip some steps.

The binary RPM created can now be installed with rpm -i or, preferably, with rpm -U. Installation with rpm makes it appear in the RPM database.

Compiling RPM Packages with build

The danger with many packages is that unwanted files are added to the running system during the build process. To prevent this use build, which creates a defined environment in which the package is built. To establish this chroot environment, the build script must be provided with a complete package tree. This tree can be made available on the hard disk, via NFS, or from DVD. Set the position with build --rpms directory. Unlike rpm, the build command looks for the SPEC file in the source directory. To build wget (like in the above example) with the DVD mounted in the system under /media/dvd, use the following commands as root:

cd /usr/src/packages/SOURCES/
mv ../SPECS/wget.spec .
build --rpms /media/dvd/suse/ wget.spec

Subsequently, a minimum environment is established at /var/tmp/build-root. The package is built in this environment. Upon completion, the resulting packages are located in /var/tmp/build-root/usr/src/packages/RPMS.

The build script offers a number of additional options. For example, cause the script to prefer your own RPMs, omit the initialization of the build environment or limit the rpm command to one of the above-mentioned stages. Access additional information with build --help and by reading the build man page.

Tools for RPM Archives and the RPM Database

Midnight Commander (mc) can display the contents of RPM archives and copy parts of them. It represents archives as virtual file systems, offering all usual menu options of Midnight Commander. Display the HEADER with F3. View the archive structure with the cursor keys and Enter. Copy archive components with F5.

KDE offers the kpackage tool as a front-end for rpm. A full-featured package manager is available as a YaST module (see Chapter 3, Installing or Removing Software).

Part III. Administration

Chapter 8. Managing Users with YaST

During installation, you chose a method for user authentication. This method is either local (via /etc/passwd) or, if a network connection is established, via NIS, LDAP, Kerberos or Samba (see “Create New User” (Chapter “Installation with YaST”, ↑Start-Up) . You can create or modify user accounts and change the authentication method with YaST at any time.

Every user is assigned a system-wide user ID (UID). Apart from the users which can log in to your machine, there are also a number of system users for internal use only. Each user is assigned to one or more groups. Similar to system users, there are also system groups for internal use. For information about the Linux user and group concept, refer to “User Concept” (Chapter “Basic Concepts”, ↑Start-Up).

User and Group Administration Dialog

To administer users or groups, start YaST and click Security and Users+User and Group Management. Alternatively, start the User and Group Administration dialog directly by running yast2 users & from a command line.

Figure 8.1. YaST User and Group Administration

Depending on the set of users you choose to view and modify with, the dialog (local users, network users, system users), the main window shows several tabs. These allow you to execute the following tasks:

Managing User Accounts

From the Users tab create, modify, delete or temporarily disable user accounts as described in Section “Managing User Accounts”. Learn about advanced options like enforcing password policies, using encrypted home directories, using fingerprint authentication, or managing disk quotas in Section “Additional Options for User Accounts”.

Changing Default Settings

Local users accounts are created according to the settings defined on the Defaults for New Users tab. Learn how to change the default group assignment, or the default path and access permissions for home directories in Section “Changing Default Settings for Local Users”.

Assigning Users to Groups

Learn how to change the group assignment for individual users in Section “Assigning Users to Groups”.

Managing Groups

From the Groups tab, you can add, modify or delete existing groups. Refer to Section “Managing Groups” for information on how to do this.

Changing the User Authentication Method

When your machine is connected to a network that provides user authentication methods like NIS or LDAP, you can choose between several authentication methods on the Authentication Settings tab. For more information, refer to Section “Changing the User Authentication Method”.

For user and group management, the dialog provides similar functionality. You can easily switch between the user and group administration view by choosing the appropriate tab at the top of the dialog.

Filter options allow you to define the set of users or groups you want to modify: On the Users or Group tab, click Set Filter to view and edit users or groups according to certain categories, such as Local Users or LDAP Users, for instance (if you are part of a network which uses LDAP). With Set Filter+Customize Filter you can also set up and use a custom filter.

Depending on the filter you choose, not all of the following options and functions will be available from the dialog.

Managing User Accounts

YaST offers to create, modify, delete or temporarily disable user accounts. Do not modify user accounts unless you are an experienced user or administrator.

Changing User IDs of Existing Users

File ownership is bound to the user ID, not to the user name. After a user ID change, the files in the user's home directory are automatically adjusted to reflect this change. However, after an ID change, the user no longer owns the files he created elsewhere in the file system unless the file ownership for those files are manually modified.

In the following, learn how to set up default user accounts. For some further options, such as auto login, login without password, setting up encrypted home directories or managing quotas for users and groups, refer to Section “Managing Quotas”.

Procedure 8.1. Adding or Modifying User Accounts

Open the YaST User and Group Administration dialog and click the Users tab.

With Set Filter define the set of users you want to manage. The dialog shows a list of users in the system and the groups the users belong to.

To modify options for an existing user, select an entry and click Edit.

To create a new user account, click Add.

Enter the appropriate user data on the first tab, such as Username (which is used for login) and Password. This data is sufficient to create a new user. If you click OK now, the system will automatically assign a user ID and set all other values according to the default.

Activate Receive System Mail if you want any kind of system notifications to be delivered to this user's mailbox. This creates a mail alias for root and the user can read the system mail without having to first log in as root.

If you want to adjust further details such as the user ID or the path to the user's home directory, do so on the Details tab.

If you need to relocate the home directory of an existing user, enter the path to the new home directory there and move the contents of the current home directory with Move to New Location. Otherwise, a new home directory is created without any of the existing data.

To force users to regularly change their password or set other password options, switch to Password Settings and adjust the options.

If all options are set according to your wishes, click OK.

Click Expert Options+Write Changes Now to save all changes without exiting the User and Group Administration dialog. Or click Finish to close the administration dialog and to save the changes. A newly added user can now log in to the system using the login name and password you created.

Matching User IDs

For a new (local) user on a laptop which also needs to integrate into a network environment where this user already has a user ID, it is useful to match the (local) user ID to the ID in the network. This ensures that the file ownership of the files the user creates “offline” is the same as if he had created them directly on the network.

Procedure 8.2. Disabling or Deleting User Accounts

Open the YaST User and Group Administration dialog and click the Users tab.

To temporarily disable a user account without deleting it, select the user from the list and click Edit. Activate Disable User Login. The user cannot log into your machine until you enable the account again.

To delete a user account, select the user from the list and click Delete. Choose if you also want to delete the user's home directory or if you want to retain the data.

Additional Options for User Accounts

In addition to the settings for a default user account, openSUSE® offers further options, such as options to enforce password policies, use encrypted home directories or define disk quotas for users and groups.

Automatic Login and Passwordless Login

If you use the KDE or GNOME desktop environment you can configure Auto Login for a certain user as well as Passwordless Login for all users. Auto login causes a user to become automatically logged in to the desktop environment on boot. This functionality can only be activated for one user at a time. Login without password allows all users to log in to the system after they have entered their username in the login manager.

Security Risk

Enabling Auto Login or Passwordless Login on a machine that can be accessed by more than one person is a security risk. Without the need to authenticate, any user can gain access to your system and your data. If your system contains confidential data, do not use this functionality.

If you want to activate auto login or login without password, access these functions in the YaST User and Group Administration with Expert Options+Login Settings.

Enforcing Password Policies

On any system with multiple users, it is a good idea to enforce at least basic password security policies. Users should change their passwords regularly and use strong passwords that cannot easily be exploited. For local users, proceed as follows:

Procedure 8.3. Configuring Password Settings

Open the YaST User and Group Administration dialog and select the Users tab.

Select the user for which to change the password options and click Edit.

Switch to the Password Settings tab.

To make the user change his password at next login, activate Force Password Change.

To enforce password rotation, set a Maximum Number of Days for the Same Password and a Minimum Number of Days for the Same Password.

To remind the user to change his password before it expires, set a number of Days before Password Expiration to Issue Warning.

To restrict the period of time the user can log in after his password has expired, change the value in Days after Password Expires with Usable Login.

You can also specify a certain expiration date for a password. Enter the Expiration Date in YYYY-MM-DD format.

For more information about the options and about the default values, click Help.

Apply your changes with OK.

Managing Encrypted Home Directories

To protect data in home directories against theft and hard disk removal, you can create encrypted home directories for users. These are encrypted with LUKS (Linux Unified Key Setup), which results in an image and an image key being generated for the user. The image key is protected with the user's login password. When the user logs into the system, the encrypted home directory is mounted and the contents are made available to the user.

Fingerprint Reader Devices and Encrypted Home Directories

If you want to use a fingerprint reader device, you must not use encrypted home directories. Otherwise logging in will fail, because decrypting during login is not possible in combination with an active fingerprint reader device.

With YaST, you can create encrypted home directories for new or existing users. To encrypt or modify encrypted home directories of already existing users, you need to know the user's current login password. By default, all existing user data is copied to the new encrypted home directory, but it is not deleted from the unencrypted directory.

Security Restrictions

Encrypting a user's home directory does not provide strong security from other users. If strong security is required, the system should not be physically shared.

Find background information about encrypted home directories and which actions to take for stronger security in “Using Encrypted Home Directories” (Chapter “Encrypting Partitions and Files”, ↑Security Guide).

Procedure 8.4. Creating Encrypted Home Directories

Open the YaST User and Group Management dialog and click the Users tab.

To encrypt the home directory of an existing user, select the user and click Edit.

Otherwise, click Add to create a new user account and enter the appropriate user data on the first tab.

In the Details tab, activate Use Encrypted Home Directory. With Directory Size in MB, specify the size of the encrypted image file to be created for this user.

Apply your settings with OK.

Enter the user's current login password to proceed if YaST prompts for it.

Click Expert Options+Write Changes Now to save all changes without exiting the administration dialog. Or click Finish to close the administration dialog and to save the changes.

Procedure 8.5. Modifying or Disabling Encrypted Home Directories

Of course, you can also disable the encryption of a home directory or change the size of the image file at any time.

Open the YaST User and Group Administration dialog in the Users view.

Select a user from the list and click Edit.

If you want to disable the encryption, switch to the Details tab and disable Use Encrypted Home Directory.

If you need to enlarge or reduce the size of the encrypted image file for this user, change the Directory Size in MB.

Apply your settings with OK.

Enter the user's current login password to proceed if YaST prompts for it.

Click Expert Options+Write Changes Now to save all changes without exiting the User and Group Administration dialog. Or click Finish to close the administration dialog and to save the changes.

Using Fingerprint Authentication

If your system includes a fingerprint reader you can use biometric authentication in addition to standard authentication via login and password. After registering their fingerprint, users can log into the system either by swiping a finger on the fingerprint reader or by typing in a password.

Fingerprints can be registered with YaST. Find detailed information about configuration and use of fingerprint authentication in “Using the Fingerprint Reader” (↑Security Guide). For a list of supported devices, refer to http://reactivated.net/fprint/wiki/Supported_devices.

Managing Quotas

To prevent system capacities from being exhausted without notification, system administrators can set up quotas for users or groups. Quotas can be defined for one or more file systems and restrict the amount of disk space that can be used and the number of inodes (index notes) that can be created there. Inodes are data structures on a file system that store basic information about a regular file, directory, or other file system object. They store all attributes of a file system object (like user and group ownership, read, write, or execute permissions), except file name and contents.

openSUSE allows usage of soft and hard quotas. Soft quotas usually define a warning level at which users are informed that they are nearing their limit, whereas hard quotas define the limit at which write requests are denied. Additionally, grace intervals can be defined that allow users or groups to temporarily violate their quotas by certain amounts.

Procedure 8.6. Enabling Quota Support for a Partition

In order to configure quotas for certain users and groups, you need to enable quota support for the respective partition in the YaST Expert Partitioner first.

In YaST, select System+Partitioner and click Yes to proceed.

In the Expert Partitioner, select the partition for which to enable quotas and click Edit.

Click Fstab Options and activate Enable Quota Support. If the quota package is not already installed, it will be installed once you confirm the respective message with Yes.

Confirm your changes and leave the Expert Partitioner.

Procedure 8.7. Setting Up Quotas for Users or Groups

Now you can define soft or hard quotas for specific users or groups and set time periods as grace intervals.

In the YaST User and Group Administration, select the user or the group you want to set the quotas for and click Edit.

On the Plug-Ins tab, select the quota entry and click Launch to open the Quota Configuration dialog.

From File System, select the partition to which the quota should apply.

Below Size Limits, restrict the amount of disk space. Enter the number of 1 KB blocks the user or group may have on this partition. Specify a Soft Limit and a Hard Limit value.

Additionally, you can restrict the number of inodes the user or group may have on the partition. Below Inodes Limits, enter a Soft Limit and Hard Limit.

You can only define grace intervals if the user or group has already exceeded the soft limit specified for size or inodes. Otherwise, the time-related input fields are not activated. Specify the time period for which the user or group is allowed to exceed the limits set above.

Confirm your settings with OK.

Click Expert Options+Write Changes Now to save all changes without exiting the User and Group Administration dialog. Or click Finish to close the administration dialog and to save the changes.

openSUSE also ships command line tools like repquota or warnquota with which system administrators can control the disk usage or send e-mail notifications to users exceeding their quota. With quota_nld, administrators can also forward kernel messages about exceeded quotas to D-BUS. For more information, refer to the repquota, the warnquota and the quota_nld man page (root password needed).

Changing Default Settings for Local Users

When creating new local users, several default settings are used by YaST. These include, for example, the primary group and the secondary groups the user belongs to, or the access permissions of the user's home directory. You can change these default settings to meet your requirements:

Open the YaST User and Group Administration dialog and select the Defaults for New Users tab.

To change the primary group the new users should automatically belong to, select another group from Default Group.

To modify the secondary groups for new users, add or change groups in Secondary Groups. The group names must be separated by commas.

If you do not want to use /home/username as default path for new users' home directories, modify the Path Prefix for Home Directory.

To change the default permission modes for newly created home directories, adjust the umask value in Umask for Home Directory. For more information about umask, refer to “Access Control Lists in Linux” (↑Security Guide) and to the umask man page.

For information about the individual options, click Help.

Apply your changes with Finish.

Assigning Users to Groups

Local users are assigned to several groups according to the default settings which you can access from the User and Group Administration dialog on the Defaults for New Users tab. In the following, learn how to modify an individual user's group assignment. If you need to change the default group assignments for new users, refer to Section “Changing Default Settings for Local Users”.

Procedure 8.8. Changing a User's Group Assignment

Open the YaST User and Group Administration dialog and click the Users tab. It shows a list of users and of the groups the users belong to.

Click Edit and switch to the Details tab.

To change the primary group the user belongs to, click Default Group and select the group from the list.

To assign the user additional secondary groups, activate the corresponding check boxes in the Additional Groups list.

Click OK to apply your changes.

Click Expert Options+Write Changes Now to save all changes without exiting the User and Group Administration dialog. Or click Finish to close the administration dialog and to save the changes.

Managing Groups

With YaST you can also easily add, modify or delete groups.

Procedure 8.9. Creating and Modifying Groups

Open the YaST User and Group Management dialog and click the Groups tab.

With Set Filter define the set of groups you want to manage. The dialog shows a list of groups in the system.

To create a new group, click Add.

To modify an existing group, select the group and click Edit.

In the following dialog, enter or change the data. The list on the right shows an overview of all available users and system users which can be members of the group.

To add existing users to a new group select them from the list of possible Group Members by checking the corresponding box. To remove them from the group just uncheck the box.

Click OK to apply your changes.

Click Expert Options+Write Changes Now to save all changes without exiting the User and Group Administration dialog.

In order to delete a group, it must not contain any group members. To delete a group, select it from the list and click Delete. Click Expert Options+Write Changes Now to save all changes without exiting the User and Group Administration dialog. Or click Finish to close the administration dialog and to save the changes.

Changing the User Authentication Method

When your machine is connected to a network, you can change the authentication method you set during installation. The following options are available:

NIS

Users are administered centrally on a NIS server for all systems in the network. For details, see “Using NIS” (↑Security Guide).

LDAP

Users are administered centrally on an LDAP server for all systems in the network. For details about LDAP, see “LDAP—A Directory Service” (↑Security Guide).

You can manage LDAP users with the YaST user module. All other LDAP settings, including the default settings for LDAP users, have to be defined with the YaST LDAP client module as described in “Configuring an LDAP Client with YaST” (Chapter “LDAP—A Directory Service”, ↑Security Guide) .

Kerberos

With Kerberos, a user registers once and then is trusted in the entire network for the rest of the session.

Samba

SMB authentication is often used in mixed Linux and Windows networks. For details, see Chapter 27, Samba and “Active Directory Support” (↑Security Guide).

To change the authentication method, proceed as follows:

Open the User and Group Administration dialog in YaST.

Click the Authentication Settings tab to show an overview of the available authentication methods and the current settings.

To change the authentication method, click Configure and select the authentication method you want to modify. This takes you directly to the client configuration modules in YaST. For information about the configuration of the appropriate client, refer to the following sections:

NIS:  “Configuring NIS Clients” (Chapter “Using NIS”, ↑Security Guide)

LDAP:  “Configuring an LDAP Client with YaST” (Chapter “LDAP—A Directory Service”, ↑Security Guide)

After accepting the configuration, return to the User and Group Administration overview.

Click Finish to close the administration dialog.

Chapter 9. Changing Language and Country Settings with YaST

Working in different countries or having to work in a multilingual environment requires your computer to be set up to support this. Use the YaST language and timezone modules to install additional system languages and adjust the country and timezone settings accordingly. The YaST language module also lets you change your system language or determine a primary language. Install secondary languages to get optional localizations if you need to start applications or desktops in languages other than the primary one. The YaST timezone module allows you to adjust your country and timezone settings and synchronize your system clock against a time server.

Changing the System Language

Depending on how you use your desktop and whether you want to switch the entire system to another language or just the desktop environment itself, there are several ways to achieve this:

Change the System Language Globally

Proceed as described in Section “Installing Additional System Languages” and Section “Switching the System Language” to install additional localized packages with YaST and set the default language. Changes are effective after relogin. To ensure that the entire system reflects the change, reboot the system or close and restart all running services, applications, and programs.

Change the Language for the Desktop Only

Provided you have previously installed the desired language packages for your desktop environment with YaST as described below, you can switch the language of your desktop using the desktop's control center. After X has been restarted, your entire desktop reflects your new choice of language. Applications not belonging to your desktop framework are not affected by this change and may still appear in the language that was set in YaST.

Temporarily Switch Languages for One Application Only

To run a single application in another language (that has already been installed with YaST), use one of the following commands:

LANG=de_DE application to start any standard X application or GNOME application in German. For other languages, use the appropriate language code. Get a list of all language codes available using the locale -av command.

KDE_LANG=de application to start any KDE application in German. For other languages, use the appropriate language code.

Installing Additional System Languages

The main language was selected during installation (see “Welcome” (Chapter “Installation with YaST”, ↑Start-Up)) and keyboard and time zone settings were adjusted. However, you can install additional languages on your system and determine which of the installed languages installed should be the default. Before installing additional languages, determine which of them should be activated after you install it. YaST knows two different language categories:

Primary Language

The primary language set in YaST applies to the entire system, including YaST and the desktop environment. This language is used whenever available unless you manually specify another language.

Secondary Languages

Secondary languages are languages selected manually for a specific situation. For example, use a secondary language to switch your KDE or GNOME desktop to a certain language or to start an application in a certain language.

Figure 9.1. Setting the Language

To install an additional language, proceed as follows:

Procedure 9.1. Installing an Additional Language

Start YaST.

Select System+Language.

Select the desired languages from the list of languages offered in Secondary Languages. When you leave this dialog with Ok, YaST installs the additional localized software packages. The system is multilingual, but you need to set the desired language explicitly to start an application in a language other than the primary one.

To make this language the default (the primary language), select it under Primary Language:

Adapt the keyboard to the new primary language and adjust the time zone, if appropriate.

Tip

For advanced keyboard or time zone settings, use the desktop control center or within YaST System+Date and Time dialog (Section “Changing the Country and Time Settings”), respectively.

Select Details to change language settings specific to root and to determine the exact locale:

Locale Settings for User root

ctype only adjusts the LC_TYPE variable in /etc/sysconfig/language for root, which sets the localization for language-specific function calls. yes sets the language for root to the same as the language for local users. no means the language settings for root are not affected by language changes. All locale values remain unset.

Use UTF-8 Encoding

Disable this box if you do not want to use UTF-8 encoding for root.

Detailed Locale Setting

If your locale was not included in the list of primary languages available, try specifying it here. However, some of these localizations may be incomplete.

Leave this dialog and apply your settings with Ok.

Switching the System Language

Switching the system language is similar to installing additional languages, described in Procedure 9.1, “Installing an Additional Language”. Use the YaST language module to change the primary language and to adjust keyboard and time zone. Once YaST has applied your changes and any open X sessions have been restarted, then YaST, applications, and the desktop reflect your new language settings.

Changing the Country and Time Settings

Use the YaST date and time module to adjust your system date, clock and time zone information to the area you are working in. Start it from the YaST Control Center by clicking System+Date and Time. First, select a general region, such as Europe. Choose an appropriate time zone that matches the one you are working in, for example, Germany.

Depending on which operating systems run on your workstation, adjust the hardware clock settings, accordingly:

If you run another operating system on your machine, such as Microsoft Windows*, it is likely your system does not use UTC, but local time. In this case, uncheck Hardware Clock Set To UTC.

If you only run Linux on your machine, set the hardware clock to UTC and have the switch form standard time to daylight saving time performed automatically.

You can change the date and time manually or opt for synchronizing your machine against an NTP server, either permanently or just for adjusting your hardware clock. If you want to set date and time manually, proceed as follows:

Figure 9.2. Setting Country and Time

Click Change to set date and time.

Select Manually and enter date and time values.

Confirm with Accept.

If you want to make use of an NTP server:

Figure 9.3. Setting Date and Time With NTP Server

Click Change to set date and time.

Select Synchronize with NTP Server.

Enter the address of an NTP server, if not already populated.

Press Synchronize Now, to get your system time set correctly. If you want to make use of NTP permanently, enable Save NTP Configuration.

Confirm with Accept.

With the Configure button, you can also open the advanced NTP configuration. For details, see Section “Configuring an NTP Client with YaST”.

Chapter 10. YaST in Text Mode

This section is intended for system administrators and experts who do not run an X server on their systems and depend on the text-based installation tool. It provides basic information about starting and operating YaST in text mode.

YaST in text mode uses the ncurses library to provide an easy pseudo-graphical user interface. The ncurses library is installed by default. The minimum supported size of the terminal emulator in which to run YaST is 80x25 characters.

Figure 10.1. Main Window of YaST in Text Mode

When you start YaST in text mode, the YaST Control Center appears (see Figure 10.1). The main window consists of three areas. The left frame features the categories to which the various modules belong. This frame is active when YaST is started and therefore it is marked by a bold white border. The active category is highlighted. The right frame provides an overview of the modules available in the active category. The bottom frame contains the buttons for Help and Quit.

When you start the YaST Control Center, the category Software is selected automatically. Use ↓ and ↑ to change the category. To select a module from the category, activate the right frame with → and then use ↓ and ↑ to select the module. Keep the arrow keys pressed to scroll through the list of available modules. The selected module is highligted. Press Enter to start the active module.

Various buttons or selection fields in the module contain a highlighted letter (yellow by default). Use Alt-highlighted_letter to select a button directly instead of navigating there with Tab. Exit the YaST Control Center by pressing Alt-Q or by selecting Quit and pressing Enter.

Navigation in Modules

The following description of the control elements in the YaST modules assumes that all function keys and Alt key combinations work and are not assigned to different global functions. Read Section “Restriction of Key Combinations” for information about possible exceptions.

Navigation among Buttons and Selection Lists

Use Tab to navigate among the buttons and frames containing selection lists. To navigate in reverse order, use Alt-Tab or Shift-Tab combinations.

Navigation in Selection Lists

Use the arrow keys (↑ and ↓) to navigate among the individual elements in an active frame containing a selection list. If individual entries within a frame exceed its width, use Shift-→ or Shift-← to scroll horizontally to the right and left. Alternatively, use Ctrl-E or Ctrl-A. This combination can also be used if using → or ← results in changing the active frame or the current selection list, as in the Control Center.

Buttons, Radio Buttons, and Check Boxes

To select buttons with empty square brackets (check boxes) or empty parentheses (radio buttons), press Space or Enter. Alternatively, radio buttons and check boxes can be selected directly with Alt-highlighted_letter. In this case, you do not need to confirm with Enter. If you navigate to an item with Tab, press Enter to execute the selected action or activate the respective menu item.

Function Keys

The F keys (F1 through F12) enable quick access to the various buttons. Available F key shortcuts are shown in the bottom line of the YaST screen. Which function keys are actually mapped to which buttons depend on the active YaST module, because the different modules offer different buttons (Details, Info, Add, Delete, etc.). Use F10 for Accept, OK, Next, and Finish. Press F1 to access the YaST help.

Using Navigation Tree in ncurses Mode

Some YaST modules use a navigation tree in the left part of the window to select configuration dialogs. Use the arrow keys (↑ and ↓) to navigate in the tree. Use Space to open or close tree items. In ncurses mode, Enter must be pressed after a selection in the navigation tree in order to show the selected dialog. This is an intentional behaviour to save time consuming redraws when browsing through the navigation tree.

Figure 10.2. The Software Installation Module

Restriction of Key Combinations

If your window manager uses global Alt combinations, the Alt combinations in YaST might not work. Keys like Alt or Shift can also be occupied by the settings of the terminal.

Replacing Alt with Esc

Alt shortcuts can be executed with Esc instead of Alt. For example, Esc H replaces Alt-H. (First press Esc, then press H.)

Backward and Forward Navigation with Ctrl-F and Ctrl-B

If the Alt and Shift combinations are occupied by the window manager or the terminal, use the combinations Ctrl-F (forward) and Ctrl-B (backward) instead.

Restriction of Function Keys

The F keys are also used for functions. Certain function keys might be occupied by the terminal and may not be available for YaST. However, the Alt key combinations and function keys should always be fully available on a pure text console.

YaST Command Line Options

Besides the text mode interface, YaST provides a pure command line interface. To get a list of YaST command line options, enter:

yast -h

Starting the Individual Modules

To save time, the individual YaST modules can be started directly. To start a module, enter:

yast <module_name>

View a list of all module names available on your system with yast -l or yast --list. Start the network module, for example, with yast lan.

Installing Packages from the Command Line

If you know a package name and the package is provided by any of your active installation repositories, you can use the command line option -i to install the package:

yast -i <package_name>

or

yast --install <package_name>

package_name can be a single short package name, for example gvim, which is installed with dependency checking, or the full path to an rpm package, which is installed without dependency checking.

If you need a command-line based software management utility with functionality beyond what YaST provides, consider using zypper. This new utility uses the same software management library that is also the foundation for the YaST package manager. The basic usage of zypper is covered in Section “Using Zypper”.

Command Line Parameters of the YaST Modules

To use YaST functionality in scripts, YaST provides command line support for individual modules. Not all modules have command line support. To display the available options of a module, enter:

yast <module_name> help

If a module does not provide command line support, the module is started in text mode and the following message appears:

This YaST module does not support the command line interface.

Chapter 11. Printer Operation

openSUSE® supports printing with many types of printers, including remote network printers. Printers can be configured manually or with YaST. For configuration instructions, refer to “Setting Up a Printer” (Chapter “Setting Up Hardware Components with YaST”, ↑Start-Up). Both graphical and command line utilities are available for starting and managing print jobs. If your printer does not work as expected, refer to Section “Troubleshooting”.

CUPS is the standard print system in openSUSE. CUPS is highly user-oriented. In many cases, it is compatible with LPRng or can be adapted with relatively little effort. LPRng is included in openSUSE only for reasons of compatibility.

Printers can be distinguished by interface, such as USB or network, and printer language. When buying a printer, make sure that the printer has an interface (like USB or parallel port) that is available on your hardware and a suitable printer language. Printers can be categorized on the basis of the following three classes of printer languages:

PostScript Printers

PostScript is the printer language in which most print jobs in Linux and Unix are generated and processed by the internal print system. This language is quite old and very efficient. If PostScript documents can be processed directly by the printer and do not need to be converted in additional stages in the print system, the number of potential error sources is reduced. Because PostScript printers are subject to substantial license costs, these printers usually cost more than printers without a PostScript interpreter.

Standard Printers (Languages Like PCL and ESC/P)

Although these printer languages are quite old, they are still undergoing expansion to address new features in printers. In the case of known printer languages, the print system can convert PostScript jobs to the respective printer language with the help of Ghostscript. This processing stage is referred to as interpreting. The best-known languages are PCL (which is mostly used by HP printers and their clones) and ESC/P (which is used by Epson printers). These printer languages are usually supported by Linux and produce an adequate print result. Linux may not be able to address some functions of extremely recent and high-end printers, because the open source developers may still be working on these features. Except for HP developing HPLIP, there are currently no printer manufacturers who develop Linux drivers and make them available to Linux distributors under an open source license. Most of these printers are in the medium price range.

Proprietary Printers (Also Called GDI Printers)

These printers do not support any of the common printer languages. They use their own undocumented printer languages, which are subject to change when a new edition of a model is released. Usually only Windows drivers are available for these printers. See Section “Printers without Standard Printer Language Support” for more information.

Before you buy a new printer, refer to the following sources to check how well the printer you intend to buy is supported:

http://www.linuxfoundation.org/OpenPrinting/

The OpenPrinting home page with the printer database. The database always show the latest Linux support status. However, a Linux distribution can only integrate the drivers available at production time. Accordingly, a printer currently rated as “perfectly supported” may not have had this status when the latest openSUSE version was released. Thus, the databases may not necessarily indicate the correct status, but only provide an approximation.

http://www.cs.wisc.edu/~ghost/

The Ghostscript Web page.

/usr/share/doc/packages/ghostscript-library/catalog.devices

List of included drivers.

The Workflow of the Printing System

The user creates a print job. The print job consists of the data to print plus information for the spooler, such as the name of the printer or the name of the printer queue, and optionally, information for the filter, such as printer-specific options.

At least one dedicated printer queue exists for every printer. The spooler holds the print job in the queue until the desired printer is ready to receive data. When the printer is ready, the spooler sends the data through the filter and back-end to the printer.

The filter converts the data generated by the application that is printing (usually PostScript or PDF, but also ASCII, JPEG, etc.) into printer-specific data (PostScript, PCL, ESC/P, etc.). The features of the printer are described in the PPD files. A PPD file contains printer-specific options with the parameters needed to enable them on the printer. The filter system makes sure that options selected by the user are enabled.

If you use a PostScript printer, the filter system converts the data into printer-specific PostScript. This does not require a printer driver. If you use a non-PostScript printer, the filter system converts the data into printer-specific data. This requires a printer driver suitable for your printer. The back-end receives the printer-specific data from the filter then passes it to the printer.

Methods and Protocols for Connecting Printers

There are various possibilities for connecting a printer to the system. The configuration of the CUPS print system does not distinguish between a local printer and a printer connected to the system over the network. In Linux, local printers must be connected as described in the manual of the printer manufacturer. CUPS supports serial, USB, parallel and SCSI connections. For more information about the printer connection, read the article CUPS in a Nutshell in the Support Database at http://en.opensuse.org/SDB:CUPS_in_a_Nutshell.

Changing Cable Connections in a Running System

When connecting the printer to the machine, do not forget that only USB devices can be plugged in or unplugged during operation. To avoid damaging your system or printer, shut down the system before changing any connections that are not USB.

Installing the Software

PPD (PostScript printer description) is the computer language that describes the properties, like resolution, and options, such as the availability of a duplex unit. These descriptions are required for using various printer options in CUPS. Without a PPD file, the print data would be forwarded to the printer in a “raw” state, which is usually not desired. During the installation of openSUSE, many PPD files are preinstalled.

To configure a PostScript printer, the best approach is to get a suitable PPD file. Many PPD files are available in the package manufacturer-PPDs, which is automatically installed within the scope of the standard installation. See Section “PPD Files in Various Packages” and Section “No Suitable PPD File Available for a PostScript Printer”.

New PPD files can be stored in the directory /usr/share/cups/model/ or added to the print system with YaST (as described in “Adding Drivers with YaST” (Chapter “Setting Up Hardware Components with YaST”, ↑Start-Up)). Subsequently, the PPD file can be selected during the installation.

Be careful if a printer manufacturer wants you to install entire software packages in addition to modifying configuration files. First, this kind of installation would result in the loss of the support provided by openSUSE and second, print commands may work differently and the system may no longer be able to address devices of other manufacturers. For this reason, the installation of manufacturer software is not recommended.

Network Printers

A network printer can support various protocols, some of them even concurrently. Although most of the supported protocols are standardized, some manufacturers expand (modify) the standard because they test systems that have not implemented the standard correctly or because they want to provide certain functions that are not available in the standard. Manufacturers then provide drivers for only a few operating systems, eliminating difficulties with those systems. Unfortunately, Linux drivers are rarely provided. The current situation is such that you cannot act on the assumption that every protocol works smoothly in Linux. Therefore, you may have to experiment with various options to achieve a functional configuration.

CUPS supports the socket, LPD, IPP and smb protocols.

socket

Socket refers to a connection in which the data is sent to an Internet socket without first performing a data handshake. Some of the socket port numbers that are commonly used are 9100 or 35. The device URI (uniform resource identifier) syntax is socket://IP.of.the.printer:port, for example, socket://192.168.2.202:9100/.

LPD (Line Printer Daemon)

The proven LPD protocol is described in RFC 1179. Under this protocol, some job-related data, such as the ID of the printer queue, is sent before the actual print data is sent. Therefore, a printer queue must be specified when configuring the LPD protocol for the data transmission. The implementations of diverse printer manufacturers are flexible enough to accept any name as the printer queue. If necessary, the printer manual should indicate what name to use. LPT, LPT1, LP1 or similar names are often used. An LPD queue can also be configured on a different Linux or Unix host in the CUPS system. The port number for an LPD service is 515. An example device URI is lpd://192.168.2.202/LPT1.

IPP (Internet Printing Protocol)

IPP is a relatively new (1999) protocol based on the HTTP protocol. With IPP, more job-related data is transmitted than with the other protocols. CUPS uses IPP for internal data transmission. This is the preferred protocol for a forwarding queue between two CUPS servers. The name of the print queue is necessary to configure IPP correctly. The port number for IPP is 631. Example device URIs are ipp://192.168.2.202/ps and ipp://192.168.2.202/printers/ps.

SMB (Windows Share)

CUPS also supports printing on printers connected to Windows shares. The protocol used for this purpose is SMB. SMB uses the port numbers 137, 138 and 139. Example device URIs are smb://user:password@workgroup/smb.example.com/printer, smb://user:password@smb.example.com/printer, and smb://smb.example.com/printer.

The protocol supported by the printer must be determined before configuration. If the manufacturer does not provide the needed information, the command nmap (which comes with the nmap package) can be used to ascertain the protocol. nmap checks a host for open ports. For example:

nmap -p 35,137-139,515,631,9100-10000 printerIP

Configuring CUPS with Command Line Tools

Apart from setting CUPS options with YaST when configuring a network printer, CUPS can be configured with command line tools like lpadmin and lpoptions. You need a device URI consisting of a back-end, such as parallel, and parameters. To determine valid device URIs on your system use the command lpinfo -v | grep ":/":

# lpinfo -v | grep ":/"
direct usb://ACME/FunPrinter%20XL
direct parallel:/dev/lp0

With lpadmin the CUPS server administrator can add, remove or manage class and print queues. To add a print queue, use the following syntax:

lpadmin -p queue -v device-URI -P PPD-file -E

Then the device (-v) is available as queue (-p), using the specified PPD file (-P). This means that you must know the PPD file and the device URI to configure the printer manually.

Do not use -E as the first option. For all CUPS commands, -E as the first argument sets use of an encrypted connection. To enable the printer, -E must be used as shown in the following example:

lpadmin -p ps -v parallel:/dev/lp0 -P \
/usr/share/cups/model/Postscript.ppd.gz -E

The following example configures a network printer:

lpadmin -p ps -v socket://192.168.2.202:9100/ -P \
/usr/share/cups/model/Postscript-level1.ppd.gz -E

For more options of lpadmin, see the man page of lpadmin(8).

During printer setup, certain options are set as default. These options can be modified for every print job (depending on the print tool used). Changing these default options with YaST is also possible. Using command line tools, set default options as follows:

First, list all options:

lpoptions -p queue -l

Example:

Resolution/Output Resolution: 150dpi *300dpi 600dpi

The activated default option is identified by a preceding asterisk (*).

Change the option with lpadmin:

lpadmin -p queue -o Resolution=600dpi

Check the new setting:

lpoptions -p queue -l

Resolution/Output Resolution: 150dpi 300dpi *600dpi

When a normal user runs lpoptions, the settings are written to ~/.cups/lpoptions. However, root settings are written to /etc/cups/lpoptions.

Graphical Printing Interfaces

Tools such as the KDE program KPrinter provide a graphical interface for choosing queues and setting both CUPS standard options and printer-specific options made available through the PPD file. You can even use KPrinter as the standard printing interface of non-KDE applications. In the print dialog of these applications, specify either kprinter or kprinter --stdin as the print command. The command to use depends on how the application transmits the data—just try which one works. If set up correctly, the application should open the KPrinter dialog whenever a print job is issued from it, so you can use the dialog to select a queue and set other printing options. This requires that the application's own print setup does not conflict with that of KPrinter and that printing options are only changed through KPrinter after it has been enabled. More information on KPrinter is available in “Managing Print Jobs” (↑KDE User Guide).

Printing from the Command Line

To print from the command line, enter lp -d queuename filename, substituting the corresponding names for queuename and filename.

Some applications rely on the lp command for printing. In this case, enter the correct command in the application's print dialog, usually without specifying filename, for example, lp -d queuename.

Special Features in openSUSE

A number of CUPS features have been adapted for openSUSE. Some of the most important changes are covered here.

CUPS and Firewall

After having performed a default installation of openSUSE, SuSEfirewall2 is active and the network interfaces are configured to be in the External Zone which blocks incoming traffic. These default settings have to be adjusted when using CUPS. More information about the SUSEfirewall2 configuration is available in “SuSEfirewall2” (Chapter “Masquerading and Firewalls”, ↑Security Guide).

CUPS Client

Normally, a CUPS client runs on a regular workstation located in a trusted network environment behind a firewall. In this case it is recommended to configure the network interface to be in the Internal Zone, so the workstation is reachable from within the network.

CUPS Server

If the CUPS server is part of a trusted network environment protected by a firewall, the network interface should be configured to be in the Internal Zone of the firewall. It is not recommended to set up a CUPS server in an untrusted network environment unless you take care that it is protected by special firewall rules and secure settings in the CUPS configuration.

PPD Files in Various Packages

The YaST printer configuration sets up the queues for CUPS using only the PPD files installed in /usr/share/cups/model. To find the suitable PPD files for the printer model, YaST compares the vendor and model determined during hardware detection with the vendors and models in all PPD files available in /usr/share/cups/model on the system. For this purpose, the YaST printer configuration generates a database from the vendor and model information extracted from the PPD files. When you select a printer, receive the PPD files matching the vendor and model from the list of models.

The configuration using only PPD files and no other information sources has the advantage that the PPD files in /usr/share/cups/model can be modified freely. The YaST printer configuration recognizes changes and regenerates the vendor and model database. For example, if you only have PostScript printers, normally you do not need the Foomatic PPD files in the cups-drivers package or the Gutenprint PPD files in the gutenprint package. Instead, the PPD files for your PostScript printers can be copied directly to /usr/share/cups/model (if they do not already exist in the manufacturer-PPDs package) to achieve an optimum configuration for your printers.

CUPS PPD Files in the cups Package

The generic PPD files in the cups package have been complemented with adapted Foomatic PPD files for PostScript level 1 and level 2 printers:

/usr/share/cups/model/Postscript-level1.ppd.gz

/usr/share/cups/model/Postscript-level2.ppd.gz

PPD Files in the cups-drivers Package

Normally, the Foomatic printer filter foomatic-rip is used together with Ghostscript for non-PostScript printers. Suitable Foomatic PPD files have the entries *NickName: ... Foomatic/Ghostscript driver and *cupsFilter: ... foomatic-rip. These PPD files are located in the cups-drivers package.

YaST generally prefers a manufacturer-PPD file. However, when no suitable manufacturer-PPD file exists, a a Foomatic PPD file with the entry *NickName: ... Foomatic ... (recommended) is selected.

Gutenprint PPD Files in the gutenprint Package

Instead of foomatic-rip, the CUPS filter rastertogutenprint from Gutenprint (formerly known as GIMP-Print) can be used for many non-PostScript printers. This filter and suitable Gutenprint PPD files are available in the gutenprint package. The Gutenprint PPD files are located in /usr/share/cups/model/gutenprint/ and have the entries *NickName: ... CUPS+Gutenprint and *cupsFilter: ... rastertogutenprint.

PPD Files from Printer Manufacturers in the manufacturer-PPDs Package

The manufacturer-PPDs package contains PPD files from printer manufacturers that are released under a sufficiently liberal license. PostScript printers should be configured with the suitable PPD file of the printer manufacturer, because this file enables the use of all functions of the PostScript printer. YaST prefers a PPD file from the manufacturer-PPDs. YaST cannot use any PPD file from the manufacturer-PPDs package if the model name does not match. This may happen if the manufacturer-PPDs package contains only one PPD file for similar models, like Funprinter 12xx series. In this case, select the respective PPD file manually in YaST.

Troubleshooting

The following sections cover some of the most frequently encountered printer hardware and software problems and ways to solve or circumvent these problems. Among the topics covered are GDI printers, PPD files and port configuration. Common network printer problems, defective printouts, and queue handling are also addressed.

Printers without Standard Printer Language Support

These printers do not support any common printer language and can only be addressed with special proprietary control sequences. Therefore they can only work with the operating system versions for which the manufacturer delivers a driver. GDI is a programming interface developed by Microsoft* for graphics devices. Usually the manufacturer delivers drivers only for Windows, and since the Windows driver uses the GDI interface these printers are also called GDI printers. The actual problem is not the programming interface, but the fact that these printers can only be addressed with the proprietary printer language of the respective printer model.

Some GDI printers can be switched to operate either in GDI mode or in one of the standard printer languages. See the manual of the printer whether this is possible. Some models require special Windows software to do the switch (note that the Windows printer driver may always switch the printer back into GDI mode when printing from Windows). For other GDI printers there are extension modules for a standard printer language available.

Some manufacturers provide proprietary drivers for their printers. The disadvantage of proprietary printer drivers is that there is no guarantee that these work with the installed print system or that they are suitable for the various hardware platforms. In contrast, printers that support a standard printer language do not depend on a special print system version or a special hardware platform.

Instead of spending time trying to make a proprietary Linux driver work, it may be more cost-effective to purchase a supported printer. This would solve the driver problem once and for all, eliminating the need to install and configure special driver software and obtain driver updates that may be required due to new developments in the print system.

No Suitable PPD File Available for a PostScript Printer

If the manufacturer-PPDs package does not contain any suitable PPD file for a PostScript printer, it should be possible to use the PPD file from the driver CD of the printer manufacturer or download a suitable PPD file from the Web page of the printer manufacturer.

If the PPD file is provided as a zip archive (.zip) or a self-extracting zip archive (.exe), unpack it with unzip. First, review the license terms of the PPD file. Then use the cupstestppd utility to check if the PPD file complies with “Adobe PostScript Printer Description File Format Specification, version 4.3.” If the utility returns “FAIL,” the errors in the PPD files are serious and are likely to cause major problems. The problem spots reported by cupstestppd should be eliminated. If necessary, ask the printer manufacturer for a suitable PPD file.

Parallel Ports

The safest approach is to connect the printer directly to the first parallel port and to select the following parallel port settings in the BIOS:

I/O address: 378 (hexadecimal)

Interrupt: irrelevant

Mode: Normal, SPP, or Output Only

DMA: disabled

If the printer cannot be addressed on the parallel port despite these settings, enter the I/O address explicitly in accordance with the setting in the BIOS in the form 0x378 in /etc/modprobe.conf. If there are two parallel ports that are set to the I/O addresses 378 and 278 (hexadecimal), enter these in the form 0x378,0x278.

If interrupt 7 is free, it can be activated with the entry shown in Example 11.1, “/etc/modprobe.conf: Interrupt Mode for the First Parallel Port”. Before activating the interrupt mode, check the file /proc/interrupts to see which interrupts are already in use. Only the interrupts currently being used are displayed. This may change depending on which hardware components are active. The interrupt for the parallel port must not be used by any other device. If you are not sure, use the polling mode with irq=none.

Example 11.1. /etc/modprobe.conf: Interrupt Mode for the First Parallel Port

alias parport_lowlevel parport_pc
options parport_pc io=0x378 irq=7

Network Printer Connections

Identifying Network Problems

Connect the printer directly to the computer. For test purposes, configure the printer as a local printer. If this works, the problems are related to the network.

Checking the TCP/IP Network

The TCP/IP network and name resolution must be functional.

Checking a Remote lpd

Use the following command to test if a TCP connection can be established to lpd (port 515) on host:

netcat -z host 515 && echo ok || echo failed

If the connection to lpd cannot be established, lpd may not be active or there may be basic network problems.

As the user root, use the following command to query a (possibly very long) status report for queue on remote host, provided the respective lpd is active and the host accepts queries:

echo -e "\004queue" \
| netcat -w 2 -p 722 host 515

If lpd does not respond, it may not be active or there may be basic network problems. If lpd responds, the response should show why printing is not possible on the queue on host. If you receive a response like that shown in Example 11.2, “Error Message from lpd”, the problem is caused by the remote lpd.

Example 11.2. Error Message from lpd

lpd: your host does not have line printer access
lpd: queue does not exist
printer: spooling disabled
printer: printing disabled

Checking a Remote cupsd

By default, the CUPS network server should broadcast its queues every 30 seconds on UDP port 631. Accordingly, the following command can be used to test whether there is a CUPS network server in the network. Make sure to stop your local CUPS daemon before executing the command.

netcat -u -l -p 631 & PID=$! ; sleep 40 ; kill $PID

If a broadcasting CUPS network server exists, the output appears as shown in Example 11.3, “Broadcast from the CUPS Network Server”.

Example 11.3. Broadcast from the CUPS Network Server

ipp://192.168.2.202:631/printers/queue

The following command can be used to test if a TCP connection can be established to cupsd (port 631) on host:

netcat -z host 631 && echo ok || echo failed

If the connection to cupsd cannot be established, cupsd may not be active or there may be basic network problems. lpstat -h host -l -t returns a (possibly very long) status report for all queues on host, provided the respective cupsd is active and the host accepts queries.

The next command can be used to test if the queue on host accepts a print job consisting of a single carriage-return character. Nothing should be printed. Possibly, a blank page may be ejected.

echo -en "\r" \
| lp -d queue -h host

Troubleshooting a Network Printer or Print Server Box

Spoolers running in a print server box sometimes cause problems when they have to deal with multiple print jobs. Since this is caused by the spooler in the print server box, there no way to resolve this issue. As a work-around, circumvent the spooler in the print server box by addressing the printer connected to the print server box directly with the TCP socket. See Section “Network Printers”.

In this way, the print server box is reduced to a converter between the various forms of data transfer (TCP/IP network and local printer connection). To use this method, you need to know the TCP port on the print server box. If the printer is connected to the print server box and turned on, this TCP port can usually be determined with the nmap utility from the nmap package some time after the print server box is powered up. For example, nmap IP-address may deliver the following output for a print server box:

Port       State       Service
23/tcp     open        telnet
80/tcp     open        http
515/tcp    open        printer
631/tcp    open        cups
9100/tcp   open        jetdirect

This output indicates that the printer connected to the print server box can be addressed via TCP socket on port 9100. By default, nmap only checks a number of commonly known ports listed in /usr/share/nmap/nmap-services. To check all possible ports, use the command nmap -p from_port-to_port IP-address. This may take some time. For further information, refer to the man page of nmap.

Enter a command like

echo -en "\rHello\r\f" | netcat -w 1 IP-address port
cat file | netcat -w 1 IP-address port

to send character strings or files directly to the respective port to test if the printer can be addressed on this port.

Defective Printouts without Error Message

For the print system, the print job is completed when the CUPS back-end completes the data transfer to the recipient (printer). If further processing on the recipient fails (for example, if the printer is not able to print the printer-specific data) the print system does not notice this. If the printer is not able to print the printer-specific data, select a PPD file that is more suitable for the printer.

Disabled Queues

If the data transfer to the recipient fails entirely after several attempts, the CUPS back-end, such as USB or socket, reports an error to the print system (to cupsd). The back-end determines how many unsuccessful attempts are appropriate until the data transfer is reported as impossible. As further attempts would be in vain, cupsd disables printing for the respective queue. After eliminating the cause of the problem, the system administrator must reenable printing with the command cupsenable.

CUPS Browsing: Deleting Print Jobs

If a CUPS network server broadcasts its queues to the client hosts via browsing and a suitable local cupsd is active on the client hosts, the client cupsd accepts print jobs from applications and forwards them to the cupsd on the server. When cupsd accepts a print job, it is assigned a new job number. Therefore, the job number on the client host is different from the job number on the server. As a print job is usually forwarded immediately, it cannot be deleted with the job number on the client host This is because the client cupsd regards the print job as completed as soon as it has been forwarded to the server cupsd.

When it becomes desirable to delete the print job on the server, use a command such as lpstat -h cups.example.com -o to determine the job number on the server, provided the server has not already completed the print job (that is, sent it completely to the printer). Using this job number, the print job on the server can be deleted:

cancel -h cups.example.com queue-jobnnumber

Defective Print Jobs and Data Transfer Errors

if you switch the printer off or shut down the computer during the printing process, print jobs remain in the queue. Printing resumes when the computer (or the printer) is switched back on. Defective print jobs must be removed from the queue with cancel.

If a print job is defective or an error occurs in the communication between the host and the printer, the printer prints numerous sheets of paper with unintelligible characters, because it is unable to process the data correctly. To rectify this situation, follow these steps:

To stop printing, remove all paper from ink jet printers or open the paper trays of laser printers. High-quality printers have a button for canceling the current printout.

The print job may still be in the queue, because jobs are only removed after they are sent completely to the printer. Use lpstat -o or lpstat -h cups.example.com -o to check which queue is currently printing. Delete the print job with cancel queue-jobnumber or cancel -h cups.example.com queue-jobnumber.

Some data may still be transferred to the printer even though the print job has been deleted from the queue. Check if a CUPS back-end process is still running for the respective queue and terminate it. For example, for a printer connected to the parallel port, the command fuser -k /dev/lp0 can be used to terminate all processes that are still accessing the printer (more precisely: the parallel port).

Reset the printer completely by switching it off for some time. Then insert the paper and turn on the printer.

Debugging the CUPS Print System

Use the following generic procedure to locate problems in the CUPS print system:

Set LogLevel debug in /etc/cups/cupsd.conf.

Stop cupsd.

Remove /var/log/cups/error_log* to avoid having to search through very large log files.

Start cupsd.

Repeat the action that led to the problem.

Check the messages in /var/log/cups/error_log* to identify the cause of the problem.

For More Information

Solutions to many specific problems are presented in the SUSE Support Database (http://en.opensuse.org/SDB:SDB). Locate the relevant articles with a text search for SDB:CUPS.

Chapter 12. Installing and Configuring Fonts for the Graphical User Interface

The installation of additional fonts in openSUSE is very easy. Simply copy the fonts to any directory located in the X11 font path (see Section “X11 Core Fonts”). To the enable use of the fonts, the installation directory should be a subdirectory of the directories configured in /etc/fonts/fonts.conf (see Section “Xft”) or included into this file with /etc/fonts/suse-font-dirs.conf.

The following is an excerpt from /etc/fonts/fonts.conf. This file is the standard configuration file that should be appropriate for most configurations. It also defines the included directory /etc/fonts/conf.d. In this directory, all files or symbolic links starting with a two digit number are loaded by fontconfig. For a more detailed explanation of this functionality, have a look at /etc/fonts/conf.d/README.

<!-- Font directory list -->
<dir>/usr/share/fonts</dir>
<dir>/usr/X11R6/lib/X11/fonts</dir>
<dir>/opt/kde3/share/fonts</dir>
<dir>/usr/local/share/fonts</dir>
<dir>~/.fonts</dir>

/etc/fonts/suse-font-dirs.conf is automatically generated to pull in fonts that ship with (mostly third party) applications like OpenOffice.org, Java or Adobe Acrobat Reader. Some typical entries of /etc/fonts/suse-font-dirs.conf would look like the following:

<dir>/usr/lib64/ooo-2.0/share/fonts</dir>
<dir>/usr/lib/jvm/java-1_4_2-sun-1.4.2.11/jre/lib/fonts</dir>
<dir>/usr/lib64/jvm/java-1.5.0-sun-1.5.0_07/jre/lib/fonts</dir>
<dir>/usr/X11R6/lib/Acrobat7/Resource/Font</dir>
<dir>/usr/X11R6/lib/Acrobat7/Resource/Font/PFM</dir>

To install additional fonts systemwide, manually copy the font files to a suitable directory (as root), such as /usr/share/fonts/truetype. Alternatively, the task can be performed with the KDE font installer in the KDE Control Center. The result is the same.

Instead of copying the actual fonts, you can also create symbolic links. For example, you may want to do this if you have licensed fonts on a mounted Windows partition and want to use them. Subsequently, run SuSEconfig --module fonts .

SuSEconfig --module fonts executes the script /usr/sbin/fonts-config, which handles the font configuration. For more information on this script, refer to its manual page (man fonts-config ).

The procedure is the same for bitmap fonts, TrueType and OpenType fonts, and Type1 (PostScript) fonts. All these font types can be installed into any directory known to fonts-config.

X.Org contains two completely different font systems: the old X11 core font system and the newly designed Xft and fontconfig system. The following sections briefly describe these two systems.

X11 Core Fonts

Today, the X11 core font system supports not only bitmap fonts but also scalable fonts, like Type1 fonts, TrueType, and OpenType fonts. Scalable fonts are only supported without antialiasing and subpixel rendering and the loading of large scalable fonts with glyphs for many languages may take a long time. Unicode fonts are also supported, but their use may be slow and require more memory.

The X11 core font system has a few inherent weaknesses. It is outdated and can no longer be extended in any meaningful way. Although it must be retained for reasons of backward compatibility, the more modern Xft and fontconfig system should be used if at all possible.

For its operation, the X server needs to know which fonts are available and where in the system it can find them. This is handled by a FontPath variable, which contains the path to all valid system font directories. In each of these directories, a file named fonts.dir lists the available fonts in this directory. The FontPath is generated by the X server at start-up. It searches for a valid fonts.dir file in each of the FontPath entries in the configuration file /etc/X11/xorg.conf. These entries are found in the Files section. Display the actual FontPath with xset q. This path may also be changed at runtime with xset. To add an additional path, use xset +fp <path>. To remove an unwanted path, use xset -fp <path>.

If the X server is already active, newly installed fonts in mounted directories can be made available with the command xset fp rehash. This command is executed by SuSEconfig --module fonts. Because the command xset needs access to the running X server, this only works if SuSEconfig --module fonts is started from a shell that has access to the running X server. The easiest way to achieve this is to aquire root permissions by entering su and the root password. su transfers the access permissions of the user who started the X server to the root shell. To check if the fonts were installed correctly and are available by way of the X11 core font system, use the command xlsfonts to list all available fonts.

By default, openSUSE uses UTF-8 locales. Therefore, Unicode fonts should be preferred (font names ending with iso10646-1 in xlsfonts output). All available Unicode fonts can be listed with xlsfonts | grep iso10646-1. Nearly all Unicode fonts available in openSUSE contain at least the glyphs needed for European languages (formerly encoded as iso-8859-*).

Xft

From the outset, the programmers of Xft made sure that scalable fonts including antialiasing are well supported. If Xft is used, the fonts are rendered by the application using the fonts, not by the X server as in the X11 core font system. In this way, the respective application has access to the actual font files and full control of how the glyphs are rendered. This constitutes the basis for the correct display of text in a number of languages. Direct access to the font files is very useful for embedding fonts for printing to make sure that the printout looks the same as the screen output.

In openSUSE, the two desktop environments (KDE and GNOME), Mozilla and many other applications already use Xft by default. Xft is already used by more applications than the old X11 core font system.

Xft uses the fontconfig library for finding fonts and influencing how they are rendered. The properties of fontconfig are controlled by the global configuration file /etc/fonts/fonts.conf. Special configurations should be added to /etc/fonts/local.conf and the user-specific configuration file ~/.fonts.conf. Each of these fontconfig configuration files must begin with

<?xml version="1.0"?>
<!DOCTYPE fontconfig SYSTEM "fonts.dtd">
<fontconfig>

and end with

</fontconfig>

To add directories to search for fonts, append lines such as the following:

<dir>/usr/local/share/fonts/</dir>

However, this is usually not necessary. By default, the user-specific directory ~/.fonts is already entered in /etc/fonts/fonts.conf. Accordingly, all you need to do to install additional fonts is to copy them to ~/.fonts.

You can also insert rules that influence the appearance of the fonts. For example, enter

<match target="font">
 <edit name="antialias" mode="assign">
  <bool>false</bool>
 </edit>
</match>

to disable antialiasing for all fonts or

<match target="font">
 <test name="family">
  <string>Luxi Mono</string>
  <string>Luxi Sans</string>
 </test>
 <edit name="antialias" mode="assign">
 <bool>false</bool>
 </edit>
</match>

to disable antialiasing for specific fonts.

By default, most applications use the font names sans-serif (or the equivalent sans), serif, or monospace. These are not real fonts but only aliases that are resolved to a suitable font, depending on the language setting.

Users can easily add rules to ~/.fonts.conf to resolve these aliases to their favorite fonts:

<alias>
 <family>sans-serif</family>
 <prefer>
  <family>FreeSans</family>
 </prefer>
</alias>
<alias>
 <family>serif</family>
 <prefer>
  <family>FreeSerif</family>
 </prefer>
</alias>
<alias>
 <family>monospace</family>
 <prefer>
  <family>FreeMono</family>
 </prefer>
</alias>

Because nearly all applications use these aliases by default, this affects almost the entire system. Thus, you can easily use your favorite fonts almost everywhere without having to modify the font settings in the individual applications.

Use the command fc-list to find out which fonts are installed and available for use. For instance, the command fc-list returns a list of all fonts. To find out which of the available scalable fonts (:scalable=true) contain all glyphs required for Hebrew (:lang=he), their font names (family), their style (style), their weight (weight) and the name of the files containing the fonts, enter the following command:

fc-list ":lang=he:scalable=true" family style weight

The output of this command could look like the following:

Lucida Sans:style=Demibold:weight=200
DejaVu Sans:style=Bold Oblique:weight=200
Lucida Sans Typewriter:style=Bold:weight=200
FreeSerif:style=Bold,polkrepko:weight=200
FreeSerif:style=Italic,ležeče:weight=80
FreeSans:style=Medium,navadno:weight=80
DejaVu Sans:style=Oblique:weight=80
FreeSans:style=Oblique,ležeče:weight=80

Important parameters that can be queried with fc-list:

Table 12.1. Parameters of fc-list

Parameter

Meaning and Possible Values

family

Name of the font family, for example, FreeSans.

foundry

The manufacturer of the font, for example, urw.

style

The font style, such as Medium, Regular, Bold, Italic or Heavy.

lang

The language that the font supports, for example, de for German, ja for Japanese, zh-TW for traditional Chinese or zh-CN for simplified Chinese.

weight

The font weight, such as 80 for regular or 200 for bold.

slant

The slant, usually 0 for none and 100 for italic.

file

The name of the file containing the font.

outline

true for outline fonts or false for other fonts.

scalable

true for scalable fonts or false for other fonts.

bitmap

true for bitmap fonts or false for other fonts.

pixelsize

Font size in pixels. In connection with fc-list, this option only makes sense for bitmap fonts.

Chapter 13. System Monitoring Utilities

Abstract

A number of programs and mechanisms, some of which are presented here, can be used to examine the status of your system. Also described are some utilities that are useful for routine work, along with their most important parameters.

For each of the commands introduced, examples of the relevant outputs are presented. In these examples, the first line is the command itself (after the > or # sign prompt). Omissions are indicated with square brackets ([...]) and long lines are wrapped where necessary. Line breaks for long lines are indicated by a backslash (\).

# command -x -y
output line 1
output line 2
output line 3 is annoyingly long, so long that \
    we have to break it
output line 3
[...]
output line 98
output line 99

The descriptions have been kept short to allow as many utilities as possible to be mentioned. Further information for all the commands can be found in the man pages. Most of the commands also understand the parameter --help, which produces a brief list of the possible parameters.

Debugging

Specifying the Required Library: ldd

Use the command ldd to find out which libraries would be loaded by the dynamic executable specified as argument.

tux@mercury:~> ldd /bin/ls
	linux-vdso.so.1 =>  (0x00007fff1ddff000)
	librt.so.1 => /lib64/librt.so.1 (0x00007f1315993000)
	libselinux.so.1 => /lib64/libselinux.so.1 (0x00007f1315776000)
	libacl.so.1 => /lib64/libacl.so.1 (0x00007f131556e000)
	libc.so.6 => /lib64/libc.so.6 (0x00007f1315215000)
	libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f1314ff9000)
	/lib64/ld-linux-x86-64.so.2 (0x00007f1315b9c000)
	libdl.so.2 => /lib64/libdl.so.2 (0x00007f1314df5000)
	libattr.so.1 => /lib64/libattr.so.1 (0x00007f1314bf0000)

Static binaries do not need any dynamic libraries.

tux@mercury:~> ldd /sbin/ldconfig
        not a dynamic executable
tux@mercury:~> file /bin/sash
/sbin/ldconfig: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), for \
 GNU/Linux 2.6.4, statically linked, stripped

Library Calls of a Program Run: ltrace

The command ltrace enables you to trace the library calls of a process. This command is used in a similar fashion to strace. The parameter -c outputs the number and duration of the library calls that have occurred:

tux@mercury:~> ltrace -c find ~
    seconds  usecs/call     calls      function
------ ----------- ----------- --------- --------------------
 57.49   40.170338        1580     25411 __fprintf_chk
 11.50    8.036963         237     33894 readdir
  7.18    5.019464          98     50822 __ctype_get_mb_cur_max
  6.02    4.206130         767      5480 fchdir
  3.30    2.304577         209     11022 malloc
  3.18    2.224551         406      5479 __open_2
[...]
  0.00    0.000025          25         1 __cxa_atexit
------ ----------- ----------- --------- --------------------
100.00   69.878004                363666 total

System Calls of a Program Run: strace

The utility strace enables you to trace all the system calls of a process currently running. Each line of the command's output contains the system call name, followed by its arguments in parenthesis, and its return value. Enter the command in the normal way, adding strace at the beginning of the line:

tux@mercury:~> strace ls
execve("/bin/ls", ["ls"], [/* 52 vars */]) = 0
brk(0)                                  = 0x618000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) \
	= 0x7f9848667000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) \
	= 0x7f9848666000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/etc/ld.so.cache", O_RDONLY)      = 3
fstat(3, {st_mode=S_IFREG|0644, st_size=200411, ...}) = 0
mmap(NULL, 200411, PROT_READ, MAP_PRIVATE, 3, 0) = 0x7f9848635000
close(3)                                = 0
open("/lib64/librt.so.1", O_RDONLY)     = 3
[...]
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) \
	= 0x7f9848508000
write(1, "bin\nDesktop\nDocuments\n", 22bin
Desktop
Documents
) = 22
close(1)                                = 0
munmap(0x7f9848508000, 4096)            = 0
close(2)                                = 0
exit_group(0)

For example, to trace all attempts to open a particular file, use the following:

tux@mercury:~> strace -e open ls .bashrc
open("/etc/ld.so.cache", O_RDONLY)       = 3
open("/lib64/librt.so.1", O_RDONLY)      = 3
open("/lib64/libselinux.so.1", O_RDONLY) = 3
open("/lib64/libacl.so.1", O_RDONLY)     = 3
open("/lib64/libc.so.6", O_RDONLY)       = 3
open("/lib64/libpthread.so.0", O_RDONLY) = 3
[...]

To trace all the child processes, use the parameter -f. The behavior and output format of strace can be largely controlled. For information, see man strace.

Files and File Systems

Determine the File Type: file

The command file determines the type of a file or a list of files by checking /usr/share/misc/magic.

tux@mercury:~> file /usr/bin/file
/usr/bin/file: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), \
    for GNU/Linux 2.6.4, dynamically linked (uses shared libs), stripped

The parameter -f list specifies a file with a list of filenames to examine. The -z allows file to look inside compressed files:

tux@mercury:~> file /usr/share/man/man1/file.1.gz
usr/share/man/man1/file.1.gz: gzip compressed data, from Unix, max compression
tux@mercury:~> file -z /usr/share/man/man1/file.1.gz
/usr/share/man/man1/file.1.gz: troff or preprocessor input text \
    (gzip compressed data, from Unix, max compression)

The parameter -i outputs a mime type string rather than the traditional description.

tux@mercury:~> file -i /usr/share/misc/magic
/usr/share/misc/magic: text/plain charset=utf-8

File Systems and Their Usage: mount, df and du

The command mount shows which file system (device and type) is mounted at which mount point:

tux@mercury:~> mount
/dev/sda3 on / type reiserfs (rw,acl,user_xattr)
proc on /proc type proc (rw)
sysfs on /sys type sysfs (rw)
udev on /dev type tmpfs (rw)
devpts on /dev/pts type devpts (rw,mode=0620,gid=5)
/dev/sda1 on /boot type ext2 (rw,acl,user_xattr)
/dev/sda4 on /local type reiserfs (rw,acl,user_xattr)
/dev/fd0 on /media/floppy type subfs (rw,nosuid,nodev,noatime,fs=floppyfss,p

Obtain information about total usage of the file systems with the command df. The parameter -h (or --human-readable) transforms the output into a form understandable for common users.

tux@mercury:~> df -h
Filesystem            Size  Used Avail Use% Mounted on
/dev/sda3              11G  3.2G  6.9G  32% /
udev                  252M  104K  252M   1% /dev
/dev/sda1              16M  6.6M  7.8M  46% /boot
/dev/sda4              27G   34M   27G   1% /local

Display the total size of all the files in a given directory and its subdirectories with the command du. The parameter -s suppresses the output of detailed information and gives only a total for each argument. -h again transforms the output into a human-readable form:

tux@mercury:~> du -sh /opt
20k    /opt

Additional Information about ELF Binaries

Read the content of binaries with the readelf utility. This even works with ELF files that were built for other hardware architectures:

tux@mercury:~> readelf --file-header /bin/ls
ELF Header:
  Magic:   7f 45 4c 46 02 01 01 00 00 00 00 00 00 00 00 00
  Class:                             ELF64
  Data:                              2's complement, little endian
  Version:                           1 (current)
  OS/ABI:                            UNIX - System V
  ABI Version:                       0
  Type:                              EXEC (Executable file)
  Machine:                           Advanced Micro Devices X86-64
  Version:                           0x1
  Entry point address:               0x402540
  Start of program headers:          64 (bytes into file)
  Start of section headers:          95720 (bytes into file)
  Flags:                             0x0
  Size of this header:               64 (bytes)
  Size of program headers:           56 (bytes)
  Number of program headers:         9
  Size of section headers:           64 (bytes)
  Number of section headers:         32
  Section header string table index: 31

File Properties: stat

The command stat displays file properties:

tux@mercury:~> stat /etc/profile
  File: `/etc/profile'
  Size: 9662      	Blocks: 24         IO Block: 4096   regular file
Device: 802h/2050d	Inode: 132349      Links: 1
Access: (0644/-rw-r--r--)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2009-03-20 07:51:17.000000000 +0100
Modify: 2009-01-08 19:21:14.000000000 +0100
Change: 2009-03-18 12:55:31.000000000 +0100

The parameter --filesystem produces details of the properties of the file system in which the specified file is located:

tux@mercury:~> stat /etc/profile --file-system
  File: "/etc/profile"
    ID: d4fb76e70b4d1746 Namelen: 255     Type: ext2/ext3
Block size: 4096       Fundamental block size: 4096
Blocks: Total: 2581445    Free: 1717327    Available: 1586197
Inodes: Total: 655776     Free: 490312

Hardware Information

PCI Resources: lspci

Accessing PCI configuration.

Most operating systems require root user privileges to grant access to the computer's PCI configuration.

The command lspci lists the PCI resources:

mercury:~ # lspci
00:00.0 Host bridge: Intel Corporation 82845G/GL[Brookdale-G]/GE/PE \
    DRAM Controller/Host-Hub Interface (rev 01)
00:01.0 PCI bridge: Intel Corporation 82845G/GL[Brookdale-G]/GE/PE \
    Host-to-AGP Bridge (rev 01)
00:1d.0 USB Controller: Intel Corporation 82801DB/DBL/DBM \
    (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #1 (rev 01)
00:1d.1 USB Controller: Intel Corporation 82801DB/DBL/DBM \
    (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #2 (rev 01)
00:1d.2 USB Controller: Intel Corporation 82801DB/DBL/DBM \
    (ICH4/ICH4-L/ICH4-M) USB UHCI Controller #3 (rev 01)
00:1d.7 USB Controller: Intel Corporation 82801DB/DBM \
    (ICH4/ICH4-M) USB2 EHCI Controller (rev 01)
00:1e.0 PCI bridge: Intel Corporation 82801 PCI Bridge (rev 81)
00:1f.0 ISA bridge: Intel Corporation 82801DB/DBL (ICH4/ICH4-L) \
    LPC Interface Bridge (rev 01)
00:1f.1 IDE interface: Intel Corporation 82801DB (ICH4) IDE \
    Controller (rev 01)
00:1f.3 SMBus: Intel Corporation 82801DB/DBL/DBM (ICH4/ICH4-L/ICH4-M) \
    SMBus Controller (rev 01)
00:1f.5 Multimedia audio controller: Intel Corporation 82801DB/DBL/DBM \
    (ICH4/ICH4-L/ICH4-M) AC'97 Audio Controller (rev 01)
01:00.0 VGA compatible controller: Matrox Graphics, Inc. G400/G450 (rev 85)
02:08.0 Ethernet controller: Intel Corporation 82801DB PRO/100 VE (LOM) \
    Ethernet Controller (rev 81)

Using -v results in a more detailed listing:

mercury:~ # lspci -v
[...]
02:08.0 Ethernet controller: Intel Corporation 82801DB PRO/100 VE (LOM)\
    Ethernet Controller (rev 81)
        Subsystem: Fujitsu Siemens Computer GmbH: Unknown device 1001
        Flags: bus master, medium devsel, latency 66, IRQ 11
        Memory at d1000000 (32-bit, non-prefetchable) [size=4K]
        I/O ports at 3000 [size=64]
        Capabilities: [dc] Power Management version 2

Information about device name resolution is obtained from the file /usr/share/pci.ids. PCI IDs not listed in this file are marked “Unknown device.”

The parameter -vv produces all the information that could be queried by the program. To view the pure numeric values, use the parameter -n.

USB Devices: lsusb

The command lsusb lists all USB devices. With the option -v, print a more detailed list. The detailed information is read from the directory /proc/bus/usb/. The following is the output of lsusb with these USB devices attached: hub, memory stick, hard disk and mouse.

mercury:/ # lsusb
Bus 004 Device 007: ID 0ea0:2168 Ours Technology, Inc. Transcend JetFlash \
    2.0 / Astone USB Drive
Bus 004 Device 006: ID 04b4:6830 Cypress Semiconductor Corp. USB-2.0 IDE \
    Adapter
Bus 004 Device 005: ID 05e3:0605 Genesys Logic, Inc.
Bus 004 Device 001: ID 0000:0000
Bus 003 Device 001: ID 0000:0000
Bus 002 Device 001: ID 0000:0000
Bus 001 Device 005: ID 046d:c012 Logitech, Inc. Optical Mouse
Bus 001 Device 001: ID 0000:0000

Networking

Show the Network Status: netstat

netstat shows network connections, routing tables (-r), interfaces (-i), masquerade connections (-M), multicast memberships (-g), and statistics (-s).

tux@mercury:~> netstat -r
Kernel IP routing table
Destination     Gateway         Genmask        Flags  MSS Window  irtt Iface
192.168.2.0     *               255.255.254.0  U        0 0          0 eth0
link-local      *               255.255.0.0    U        0 0          0 eth0
loopback        *               255.0.0.0      U        0 0          0 lo
default         192.168.2.254   0.0.0.0        UG       0 0          0 eth0

tux@mercury:~> netstat -i
Kernel Interface table
Iface   MTU Met   RX-OK RX-ERR RX-DRP RX-OVR  TX-OK TX-ERR TX-DRP TX-OVR Flg
eth0   1500   0 1624507 129056      0      0   7055      0      0      0 BMNRU
lo    16436   0   23728      0      0      0  23728      0      0      0 LRU

When displaying network connections or statistics, you can specify the socket type to display: TCP (-t), UDP (-u), or raw (-r). The -p option shows the PID and name of the program to which each socket belongs.

The following example lists all TCP connections and the programs using these connections.

mercury:~ # netstat -t -p
Active Internet connections (w/o servers)
Proto Recv-Q Send-Q Local Address  Foreign Address       State       PID/Pro

tcp      0      0 mercury:33513    www.novell.com:www-http ESTABLISHED 6862/fi
tcp      0    352 mercury:ssh      mercury2.:trc-netpoll     ESTABLISHED 19422/s
tcp      0      0 localhost:ssh  localhost:17828         ESTABLISHED -

In the following, statistics for the TCP protocol are displayed:

tux@mercury:~> netstat -s -t
Tcp:
    2427 active connections openings
    2374 passive connection openings
    0 failed connection attempts
    0 connection resets received
    1 connections established
    27476 segments received
    26786 segments send out
    54 segments retransmited
    0 bad segments received.
    6 resets sent
[...]
    TCPAbortOnLinger: 0
    TCPAbortFailed: 0
    TCPMemoryPressures: 0

Interactive Network Monitor: iptraf

The iptraf utility is a menu based LAN (Local Area Network) monitor. It generates network satistics, including TCP and UDP counts, Ethernet load information, IP checksum errors and others.

If you enter the command without any option, it runs in interactive mode. You can navigate through graphical menus and choose the statistics that you want iptraf to report. It is also possible to specify which network interface should be examined.

Figure 13.1. iptraf Running in Interactive Mode

The command iptraf understands several options and can be run in a batch mode as well. The following example will collect statistics for network interface eth0 (-i) for 1 minute (-t). It will be run in the background (-B) and the statistics will be written to the iptraf.log file in your home directory (-L).

tux@mercury:~> iptraf -i eth0 -t 1 -B -L ~/iptraf.log

You can examine the log file with the more command:

tux@mercury:~> more ~/iptraf.log
Mon Mar 23 10:08:02 2009; ******** IP traffic monitor started ********
Mon Mar 23 10:08:02 2009; UDP; eth0; 107 bytes; from 192.168.1.192:33157 to \
 239.255.255.253:427
Mon Mar 23 10:08:02 2009; VRRP; eth0; 46 bytes; from 192.168.1.252 to \
 224.0.0.18
Mon Mar 23 10:08:03 2009; VRRP; eth0; 46 bytes; from 192.168.1.252 to \
 224.0.0.18
Mon Mar 23 10:08:03 2009; VRRP; eth0; 46 bytes; from 192.168.1.252 to \
 224.0.0.18
[..]
Mon Mar 23 10:08:06 2009; UDP; eth0; 132 bytes; from 192.168.1.54:54395 to \
 10.20.7.255:111
Mon Mar 23 10:08:06 2009; UDP; eth0; 46 bytes; from 192.168.1.92:27258 to \
 10.20.7.255:8765
Mon Mar 23 10:08:06 2009; UDP; eth0; 124 bytes; from 192.168.1.139:43464 to \
 10.20.7.255:111
Mon Mar 23 10:08:06 2009; VRRP; eth0; 46 bytes; from 192.168.1.252 to \
 224.0.0.18
--More--(7%)

The /proc File System

The /proc file system is a pseudo file system in which the kernel reserves important information in the form of virtual files. For example, display the CPU type with this command:

tux@mercury:~> cat /proc/cpuinfo
processor       : 0
vendor_id       : GenuineIntel
cpu family      : 15
model           : 4
model name      : Intel(R) Pentium(R) 4 CPU 3.40GHz
stepping        : 3
cpu MHz         : 2800.000
cache size      : 2048 KB
physical id     : 0
[...]

Query the allocation and use of interrupts with the following command:

tux@mercury:~> cat /proc/interrupts
           CPU0
  0:    3577519          XT-PIC  timer
  1:        130          XT-PIC  i8042
  2:          0          XT-PIC  cascade
  5:     564535          XT-PIC  Intel 82801DB-ICH4
  7:          1          XT-PIC  parport0
  8:          2          XT-PIC  rtc
  9:          1          XT-PIC  acpi, uhci_hcd:usb1, ehci_hcd:usb4
 10:          0          XT-PIC  uhci_hcd:usb3
 11:      71772          XT-PIC  uhci_hcd:usb2, eth0
 12:     101150          XT-PIC  i8042
 14:      33146          XT-PIC  ide0
 15:     149202          XT-PIC  ide1
NMI:          0
LOC:          0
ERR:          0
MIS:          0

Some of the important files and their contents are:

/proc/devices

Available devices

/proc/modules

Kernel modules loaded

/proc/cmdline

Kernel command line

/proc/meminfo

Detailed information about memory usage

/proc/config.gz

gzip-compressed configuration file of the kernel currently running

Further information is available in the text file /usr/src/linux/Documentation/filesystems/proc.txt (this file is available when the package kernel-source is installed). Find information about processes currently running in the /proc/NNN directories, where NNN is the process ID (PID) of the relevant process. Every process can find its own characteristics in /proc/self/:

tux@mercury:~> ls -l /proc/self
lrwxrwxrwx 1 root root 64 2007-07-16 13:03 /proc/self -> 5356
tux@mercury:~> ls -l /proc/self/
total 0
dr-xr-xr-x 2 tux users 0 2007-07-16 17:04 attr
-r-------- 1 tux users 0 2007-07-16 17:04 auxv
-r--r--r-- 1 tux users 0 2007-07-16 17:04 cmdline
lrwxrwxrwx 1 tux users 0 2007-07-16 17:04 cwd -> /home/tux
-r-------- 1 tux users 0 2007-07-16 17:04 environ
lrwxrwxrwx 1 tux users 0 2007-07-16 17:04 exe -> /bin/ls
dr-x------ 2 tux users 0 2007-07-16 17:04 fd
-rw-r--r-- 1 tux users 0 2007-07-16 17:04 loginuid
-r--r--r-- 1 tux users 0 2007-07-16 17:04 maps
-rw------- 1 tux users 0 2007-07-16 17:04 mem
-r--r--r-- 1 tux users 0 2007-07-16 17:04 mounts
-rw-r--r-- 1 tux users 0 2007-07-16 17:04 oom_adj
-r--r--r-- 1 tux users 0 2007-07-16 17:04 oom_score
lrwxrwxrwx 1 tux users 0 2007-07-16 17:04 root -> /
-rw------- 1 tux users 0 2007-07-16 17:04 seccomp
-r--r--r-- 1 tux users 0 2007-07-16 17:04 smaps
-r--r--r-- 1 tux users 0 2007-07-16 17:04 stat
[...]
dr-xr-xr-x 3 tux users 0 2007-07-16 17:04 task
-r--r--r-- 1 tux users 0 2007-07-16 17:04 wchan

The address assignment of executables and libraries is contained in the maps file:

tux@mercury:~> cat /proc/self/maps
08048000-0804c000 r-xp 00000000 03:03 17753      /bin/cat
0804c000-0804d000 rw-p 00004000 03:03 17753      /bin/cat
0804d000-0806e000 rw-p 0804d000 00:00 0          [heap]
b7d27000-b7d5a000 r--p 00000000 03:03 11867      /usr/lib/locale/en_GB.utf8/
b7d5a000-b7e32000 r--p 00000000 03:03 11868      /usr/lib/locale/en_GB.utf8/
b7e32000-b7e33000 rw-p b7e32000 00:00 0
b7e33000-b7f45000 r-xp 00000000 03:03 8837       /lib/libc-2.3.6.so
b7f45000-b7f46000 r--p 00112000 03:03 8837       /lib/libc-2.3.6.so
b7f46000-b7f48000 rw-p 00113000 03:03 8837       /lib/libc-2.3.6.so
b7f48000-b7f4c000 rw-p b7f48000 00:00 0
b7f52000-b7f53000 r--p 00000000 03:03 11842      /usr/lib/locale/en_GB.utf8/
[...]
b7f5b000-b7f61000 r--s 00000000 03:03 9109       /usr/lib/gconv/gconv-module
b7f61000-b7f62000 r--p 00000000 03:03 9720       /usr/lib/locale/en_GB.utf8/
b7f62000-b7f76000 r-xp 00000000 03:03 8828       /lib/ld-2.3.6.so
b7f76000-b7f78000 rw-p 00013000 03:03 8828       /lib/ld-2.3.6.so
bfd61000-bfd76000 rw-p bfd61000 00:00 0          [stack]
ffffe000-fffff000 ---p 00000000 00:00 0          [vdso]

procinfo

Important information from the /proc file system is summarized by the command procinfo:

tux@mercury:~> procinfo
Linux 2.6.18.8-0.5-default (geeko@buildhost) (gcc 4.1.2 20061115) #1 2CPU

Memory:      Total        Used        Free      Shared     Buffers
Mem:       2060604     2011264       49340           0      200664
Swap:      2104472         112     2104360

Bootup: Tue Jul 10 10:29:15 2007    Load average: 0.86 1.10 1.11 3/118 21547

user  :       2:43:13.78   0.8%  page in :   71099181  disk 1:  2827023r 968
nice  :   1d 22:21:27.87  14.7%  page out:  690734737
system:      13:39:57.57   4.3%  page act:  138388345
IOwait:      18:02:18.59   5.7%  page dea:   29639529
hw irq:       0:03:39.44   0.0%  page flt: 9539791626
sw irq:       1:15:35.25   0.4%  swap in :         69
idle  :   9d 16:07:56.79  73.8%  swap out:        209
uptime:   6d 13:07:11.14         context :  542720687

irq  0: 141399308 timer          irq 14:   5074312 ide0
irq  1:     73784 i8042          irq 50:   1938076 uhci_hcd:usb1, ehci_
irq  4:         2                irq 58:         0 uhci_hcd:usb2
irq  6:         5 floppy [2]     irq 66:    872711 uhci_hcd:usb3, HDA I
irq  7:         2                irq 74:        15 uhci_hcd:usb4
irq  8:         0 rtc            irq 82: 178717720 0         PCI-MSI  e
irq  9:         0 acpi           irq169:  44352794 nvidia
irq 12:         3                irq233:   8209068 0         PCI-MSI  l

To see all the information, use the parameter -a. The parameter -nN produces updates of the information every N seconds. In this case, terminate the program by pressing Q.

By default, the cumulative values are displayed. The parameter -d produces the differential values. procinfo -dn5 displays the values that have changed in the last five seconds:

Processes

Interprocess Communication: ipcs

The command ipcs produces a list of the IPC resources currently in use:

------ Shared Memory Segments --------
key        shmid      owner     perms      bytes      nattch     status
0x00000000 58261504   tux    600        393216     2          dest
0x00000000 58294273   tux    600        196608     2          dest
0x00000000 83886083   tux    666        43264      2
0x00000000 83951622   tux    666        192000     2
0x00000000 83984391   tux    666        282464     2
0x00000000 84738056   root      644        151552     2          dest

------ Semaphore Arrays --------
key        semid      owner     perms      nsems
0x4d038abf 0          tux    600        8

------ Message Queues --------
key        msqid      owner      perms      used-bytes   messages

Process List: ps

The command ps produces a list of processes. Most parameters must be written without a minus sign. Refer to ps --help for a brief help or to the man page for extensive help.

To list all processes with user and command line information, use ps axu:

tux@mercury:~> ps axu
USER       PID %CPU %MEM    VSZ   RSS TTY      STAT START   TIME COMMAND
root         1  0.0  0.0    696   272 ?        S    12:59   0:01 init [5]
root         2  0.0  0.0      0     0 ?        SN   12:59   0:00 [ksoftirqd
root         3  0.0  0.0      0     0 ?        S<   12:59   0:00 [events
[...]
tux    4047  0.0  6.0 158548 31400 ?        Ssl  13:02   0:06 mono-best
tux    4057  0.0  0.7   9036  3684 ?        Sl   13:02   0:00 /opt/gnome
tux    4067  0.0  0.1   2204   636 ?        S    13:02   0:00 /opt/gnome
tux    4072  0.0  1.0  15996  5160 ?        Ss   13:02   0:00 gnome-scre
tux    4114  0.0  3.7 130988 19172 ?        SLl  13:06   0:04 sound-juic
tux    4818  0.0  0.3   4192  1812 pts/0    Ss   15:59   0:00 -bash
tux    4959  0.0  0.1   2324   816 pts/0    R+   16:17   0:00 ps axu

To check how many sshd processes are running, use the option -p together with the command pidof, which lists the process IDs of the given processes.

tux@mercury:~> ps -p $(pidof sshd)
  PID TTY      STAT   TIME COMMAND
 3524 ?        Ss     0:00 /usr/sbin/sshd -o PidFile=/var/run/sshd.init.pid
 4813 ?        Ss     0:00 sshd: tux [priv]
 4817 ?        R      0:00 sshd: tux@pts/0

The process list can be formatted according to your needs. The option -L returns a list of all keywords. Enter the following command to issue a list of all processes sorted by memory usage:

tux@mercury:~> ps ax --format pid,rss,cmd --sort rss
  PID   RSS CMD
    2     0 [ksoftirqd/0]
    3     0 [events/0]
    4     0 [khelper]
    5     0 [kthread]
   11     0 [kblockd/0]
   12     0 [kacpid]
  472     0 [pdflush]
  473     0 [pdflush]
[...]
 4028 17556 nautilus --no-default-window --sm-client-id default2
 4118 17800 ksnapshot
 4114 19172 sound-juicer
 4023 25144 gnome-panel --sm-client-id default1
 4047 31400 mono-best --debug /usr/lib/beagle/Best.exe --autostarted
 3973 31520 mono-beagled --debug /usr/lib/beagle/BeagleDaemon.exe --bg --aut

Process Tree: pstree

The command pstree produces a list of processes in the form of a tree:

tux@mercury:~> pstree
init-+-NetworkManagerD
     |-acpid
     |-3*[automount]
     |-cron
     |-cupsd
     |-2*[dbus-daemon]
     |-dbus-launch
     |-dcopserver
     |-dhcpcd
     |-events/0
     |-gpg-agent
     |-hald-+-hald-addon-acpi
     |      `-hald-addon-stor
     |-kded
     |-kdeinit-+-kdesu---su---kdesu_stub---yast2---y2controlcenter
     |         |-kio_file
     |         |-klauncher
     |         |-konqueror
     |         |-konsole-+-bash---su---bash
     |         |         `-bash
     |         `-kwin
     |-kdesktop---kdesktop_lock---xmatrix
     |-kdesud
     |-kdm-+-X
     |     `-kdm---startkde---kwrapper
[...]

The parameter -p adds the process ID to a given name. To have the command lines displayed as well, use the -a parameter:

Processes: top

The command top, which stands for "table of processes," displays a list of processes that is refreshed every two seconds. To terminate the program, press Q. The parameter -n 1 terminates the program after a single display of the process list. The following is an example output of the command top -n 1:

tux@mercury:~> top -n 1
top - 17:06:28 up  2:10,  5 users,  load average: 0.00, 0.00, 0.00
Tasks:  85 total,   1 running,  83 sleeping,   1 stopped,   0 zombie
Cpu(s):  5.5% us,  0.8% sy,  0.8% ni, 91.9% id,  1.0% wa,  0.0% hi,  0.0% si
Mem:    515584k total,   506468k used,     9116k free,    66324k buffers
Swap:   658656k total,        0k used,   658656k free,   353328k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
    1 root      16   0   700  272  236 S  0.0  0.1   0:01.33 init
    2 root      34  19     0    0    0 S  0.0  0.0   0:00.00 ksoftirqd/0
    3 root      10  -5     0    0    0 S  0.0  0.0   0:00.27 events/0
    4 root      10  -5     0    0    0 S  0.0  0.0   0:00.01 khelper
    5 root      10  -5     0    0    0 S  0.0  0.0   0:00.00 kthread
   11 root      10  -5     0    0    0 S  0.0  0.0   0:00.05 kblockd/0
   12 root      20  -5     0    0    0 S  0.0  0.0   0:00.00 kacpid
  472 root      20   0     0    0    0 S  0.0  0.0   0:00.00 pdflush
  473 root      15   0     0    0    0 S  0.0  0.0   0:00.06 pdflush
  475 root      11  -5     0    0    0 S  0.0  0.0   0:00.00 aio/0
  474 root      15   0     0    0    0 S  0.0  0.0   0:00.07 kswapd0
  681 root      10  -5     0    0    0 S  0.0  0.0   0:00.01 kseriod
  839 root      10  -5     0    0    0 S  0.0  0.0   0:00.02 reiserfs/0
  923 root      13  -4  1712  552  344 S  0.0  0.1   0:00.67 udevd
 1343 root      10  -5     0    0    0 S  0.0  0.0   0:00.00 khubd
 1587 root      20   0     0    0    0 S  0.0  0.0   0:00.00 shpchpd_event
 1746 root      15   0     0    0    0 S  0.0  0.0   0:00.00 w1_control
 1752 root      15   0     0    0    0 S  0.0  0.0   0:00.00 w1_bus_master1
 2151 root      16   0  1464  496  416 S  0.0  0.1   0:00.00 acpid
 2165 messageb  16   0  3340 1048  792 S  0.0  0.2   0:00.64 dbus-daemon
 2166 root      15   0  1840  752  556 S  0.0  0.1   0:00.01 syslog-ng
 2171 root      16   0  1600  516  320 S  0.0  0.1   0:00.00 klogd
 2235 root      15   0  1736  800  652 S  0.0  0.2   0:00.10 resmgrd
 2289 root      16   0  4192 2852 1444 S  0.0  0.6   0:02.05 hald
 2403 root      23   0  1756  600  524 S  0.0  0.1   0:00.00 hald-addon-acpi
 2709 root      19   0  2668 1076  944 S  0.0  0.2   0:00.00 NetworkManagerD
 2714 root      16   0  1756  648  564 S  0.0  0.1   0:00.56 hald-addon-stor

If you press F while top is running, a menu opens with which to make extensive changes to the format of the output.

The parameter -U UID monitors only the processes associated with a particular user. Replace UID with the user ID of the user. top -U $(id -u) returns the UID of the user on the basis of the username and displays the user's processes.

Modify a process' niceness: nice and renice

The kernel determines which processes require more cpu time than others by the process' nice level, also called niceness. The higher the “nice” level of a process is, the less CPU time it will take from other processes. Nice levels range from -20 (the least “nice” level) to 19. Negative values can only set by root.

Adjusting the niceness level is useful when running a non time-critical process that lasts long and uses large amounts of CPU time, such as compiling a kernel, on a system that also performs other tasks. Making such a process “nicer”, ensures that the other tasks, for example a webserver, will have a higher priority.

Calling nice without any parameters prints the current niceness:

tux@mercury:~> nice
0

Running nice command increments the current nice level for the given command by 10. Using nice -n level command lets you specify a new niceness relative to the current one.

To change the niceness of a running process, use renice priority -p process id, for example:

renice +5 3266

To renice all processes owned by a specific user, use the option -u user. Process groups are reniced by the option -g process group id.

System Information

System Activity Information: sar

To use sar, sadc (system activity data collector) needs to be running. Check its status or start it with rcsysstat {start|status}.

sar can generate extensive reports on almost all important system activities, among them CPU, memory, IRQ usage, IO, or networking. With its many options, it is too complex to explain further here. Refer to the man page for extensive documentation with examples.

Device Load Information: iostat

iostat monitors the system device loading. It generates reports that can be useful for better balancing the load between physical disks attached to your system.

The first iostat report shows statistics collected since the system was booted. Subsequent reports cover the time since the previous report.

tux@mercury:~> iostat
Linux 2.6.27.19-3.2-default (geeko@buildhost) 	23.3.2009 	_x86_64_

avg-cpu:  %user   %nice %system %iowait  %steal   %idle
           0,49    0,01    0,10    0,31    0,00   99,09

Device:            tps   Blk_read/s   Blk_wrtn/s   Blk_read   Blk_wrtn
sda               1,34         5,59        25,37    1459766    6629160
sda1              0,00         0,01         0,00       1519          0
sda2              0,87         5,11        17,83    1335365    4658152
sda3              0,47         0,47         7,54     122578    1971008

When invoked with the -n option, iostat adds statistics of network filesystems (NFS) load. The option -x shows extended statistics information.

You can also specify which device should be monitored at what time intervals. For example, iostat -p sda 3 5 will display five reports at three second intervals for device sda.

Processor Activity Monitoring: mpstat

The utility mpstat examines activities of each available processor. If your system has one processor only, the global average statistics will be reported.

With the -P option, you can specify the number of processors to be reported (note that 0 is the first processor). The timing arguments work the same way as in the case of iostat command. Entering mpstat -P 1 2 5 prints five reports for the second processor (number 1) at 2 second intervals.

tux@mercury:~> mpstat -P 1 2 5
Linux 2.6.27.19-5-default (geeko@buildhost) 	03/23/2009 	_x86_64_

08:57:10 AM  CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  \
 %guest   %idle
08:57:12 AM    1    4.46    0.00    5.94    0.50    0.00    0.00    0.00  \
 0.00   89.11
08:57:14 AM    1    1.98    0.00    2.97    0.99    0.00    0.99    0.00  \
 0.00   93.07
08:57:16 AM    1    2.50    0.00    3.00    0.00    0.00    1.00    0.00  \
 0.00   93.50
08:57:18 AM    1   14.36    0.00    1.98    0.00    0.00    0.50    0.00  \
 0.00   83.17
08:57:20 AM    1    2.51    0.00    4.02    0.00    0.00    2.01    0.00  \
 0.00   91.46
Average:       1    5.17    0.00    3.58    0.30    0.00    0.90    0.00  \
 0.00   90.05

Task Monitoring: pidstat

If you need to see what load a particular task applies to your system, use pidstat command. It prints activity of every selected task or all tasks managed by Linux kernel if no task is specified. You can also set the number of reports to be displayed and the time interval between them.

For example, pidstat -C top 2 3 prints the load statistic for tasks whose command name includes the string “top”. There will be three reports printed at two second intervals.

tux@mercury:~> pidstat -C top 2 3
Linux 2.6.27.19-5-default (geeko@buildhost) 	03/23/2009 	_x86_64_

09:25:42 AM       PID    %usr %system  %guest    %CPU   CPU  Command
09:25:44 AM     23576   37.62   61.39    0.00   99.01     1  top

09:25:44 AM       PID    %usr %system  %guest    %CPU   CPU  Command
09:25:46 AM     23576   37.00   62.00    0.00   99.00     1  top

09:25:46 AM       PID    %usr %system  %guest    %CPU   CPU  Command
09:25:48 AM     23576   38.00   61.00    0.00   99.00     1  top

Average:          PID    %usr %system  %guest    %CPU   CPU  Command
Average:        23576   37.54   61.46    0.00   99.00     -  top

Memory Usage: free

The utility free examines RAM usage. Details of both free and used memory and swap areas are shown:

tux@mercury:~> free
            total       used       free     shared    buffers     cached
Mem:       2062844    2047444      15400          0     129580     921936
-/+ buffers/cache:     995928    1066916
Swap:      2104472          0    2104472

The options -b,-k,-m,-g show output in bytes, KB, MB, or GB, respectively. The parameter -d delay ensures that the display is refreshed every delay seconds. For example, free -d 1.5 produces an update every 1.5 seconds.

User Accessing Files: fuser

It can be useful to determine what processes or users are currently accessing certain files. Suppose, for example, you want to unmount a file system mounted at /mnt. umount returns "device is busy." The command fuser can then be used to determine what processes are accessing the device:

tux@mercury:~> fuser -v /mnt/*

                     USER        PID ACCESS COMMAND
/mnt/notes.txt       tux    26597 f....  less

Following termination of the less process, which was running on another terminal, the file system can successfully be unmounted. When used with -k option, fuser will kill processes accessing the file as well.

Kernel Ring Buffer: dmesg

The Linux kernel keeps certain messages in a ring buffer. To view these messages, enter the command dmesg:

tux@mercury:~> dmesg
[...]
end_request: I/O error, dev fd0, sector 0
subfs: unsuccessful attempt to mount media (256)
e100: eth0: e100_watchdog: link up, 100Mbps, half-duplex
NET: Registered protocol family 17
IA-32 Microcode Update Driver: v1.14 <tigran@veritas.com>
microcode: CPU0 updated from revision 0xe to 0x2e, date = 08112004
IA-32 Microcode Update Driver v1.14 unregistered
bootsplash: status on console 0 changed to on
NET: Registered protocol family 10
Disabled Privacy Extensions on device c0326ea0(lo)
IPv6 over IPv4 tunneling driver
powernow: This module only works with AMD K7 CPUs
bootsplash: status on console 0 changed to on

Older events are logged in the files /var/log/messages and /var/log/warn.

List of Open Files: lsof

To view a list of all the files open for the process with process ID PID, use -p. For example, to view all the files used by the current shell, enter:

tux@mercury:~> lsof -p $$
COMMAND  PID   USER   FD   TYPE DEVICE    SIZE   NODE NAME
bash    5552 tux  cwd    DIR    3,3    1512 117619 /home/tux
bash    5552 tux  rtd    DIR    3,3     584      2 /
bash    5552 tux  txt    REG    3,3  498816  13047 /bin/bash
bash    5552 tux  mem    REG    0,0              0 [heap] (stat: No such
bash    5552 tux  mem    REG    3,3  217016 115687 /var/run/nscd/passwd
bash    5552 tux  mem    REG    3,3  208464  11867 /usr/lib/locale/en_GB.
[..]
bash    5552 tux  mem    REG    3,3     366   9720 /usr/lib/locale/en_GB.
bash    5552 tux  mem    REG    3,3   97165   8828 /lib/ld-2.3.6.so
bash    5552 tux    0u   CHR  136,5              7 /dev/pts/5
bash    5552 tux    1u   CHR  136,5              7 /dev/pts/5
bash    5552 tux    2u   CHR  136,5              7 /dev/pts/5
bash    5552 tux  255u   CHR  136,5              7 /dev/pts/5

The special shell variable $$, whose value is the process ID of the shell, has been used.

The command lsof lists all the files currently open when used without any parameters. Because there are often thousands of open files, listing all of them is rarely useful. However, the list of all files can be combined with search functions to generate useful lists. For example, list all used character devices:

tux@mercury:~> lsof | grep CHR
bash      3838     tux    0u      CHR  136,0                 2 /dev/pts/0
bash      3838     tux    1u      CHR  136,0                 2 /dev/pts/0
bash      3838     tux    2u      CHR  136,0                 2 /dev/pts/0
bash      3838     tux  255u      CHR  136,0                 2 /dev/pts/0
bash      5552     tux    0u      CHR  136,5                 7 /dev/pts/5
bash      5552     tux    1u      CHR  136,5                 7 /dev/pts/5
bash      5552     tux    2u      CHR  136,5                 7 /dev/pts/5
bash      5552     tux  255u      CHR  136,5                 7 /dev/pts/5
X         5646       root  mem       CHR    1,1              1006 /dev/mem
lsof      5673     tux    0u      CHR  136,5                 7 /dev/pts/5
lsof      5673     tux    2u      CHR  136,5                 7 /dev/pts/5
grep      5674     tux    1u      CHR  136,5                 7 /dev/pts/5
grep      5674     tux    2u      CHR  136,5                 7 /dev/pts/5

When used with -i, lsof lists currently open Internet files as well:

tux@mercury:~> lsof -i
pidgin     4349 tux   17r  IPv4  15194      0t0  TCP \
 jupiter.example.com:58542->www.example.net:https (ESTABLISHED)
pidgin     4349 tux   21u  IPv4  15583      0t0  TCP \
 jupiter.example.com:37051->aol.example.org:aol (ESTABLISHED)
evolution  4578 tux   38u  IPv4  16102      0t0  TCP \
 jupiter.example.com:57419->imap.example.com:imaps (ESTABLISHED)
npviewer.  9425 tux   40u  IPv4  24769      0t0  TCP \
 jupiter.example.com:51416->www.example.com:http (CLOSE_WAIT)
npviewer.  9425 tux   49u  IPv4  24814      0t0  TCP \
 jupiter.example.com:43964->www.example.org:http (CLOSE_WAIT)
ssh       17394 tux    3u  IPv4  40654      0t0  TCP \
 jupiter.example.com:35454->saturn.example.com:ssh (ESTABLISHED)

Kernel and udev Event Sequence Viewer: udevadm monitor

udevadm monitor listens to the kernel uevents and events sent out by a udev rule and prints the device path (DEVPATH) of the event to the console. This is a sequence of events while connecting a USB memory stick:

Monitoring udev events.

Only root user is allowed to monitor udev events by running udevadm command.

UEVENT[1138806687] add@/devices/pci0000:00/0000:00:1d.7/usb4/4-2/4-2.2
UEVENT[1138806687] add@/devices/pci0000:00/0000:00:1d.7/usb4/4-2/4-2.2/4-2.2
UEVENT[1138806687] add@/class/scsi_host/host4
UEVENT[1138806687] add@/class/usb_device/usbdev4.10
UDEV  [1138806687] add@/devices/pci0000:00/0000:00:1d.7/usb4/4-2/4-2.2
UDEV  [1138806687] add@/devices/pci0000:00/0000:00:1d.7/usb4/4-2/4-2.2/4-2.2
UDEV  [1138806687] add@/class/scsi_host/host4
UDEV  [1138806687] add@/class/usb_device/usbdev4.10
UEVENT[1138806692] add@/devices/pci0000:00/0000:00:1d.7/usb4/4-2/4-2.2/4-2.2
UEVENT[1138806692] add@/block/sdb
UEVENT[1138806692] add@/class/scsi_generic/sg1
UEVENT[1138806692] add@/class/scsi_device/4:0:0:0
UDEV  [1138806693] add@/devices/pci0000:00/0000:00:1d.7/usb4/4-2/4-2.2/4-2.2
UDEV  [1138806693] add@/class/scsi_generic/sg1
UDEV  [1138806693] add@/class/scsi_device/4:0:0:0
UDEV  [1138806693] add@/block/sdb
UEVENT[1138806694] add@/block/sdb/sdb1
UDEV  [1138806694] add@/block/sdb/sdb1
UEVENT[1138806694] mount@/block/sdb/sdb1
UEVENT[1138806697] umount@/block/sdb/sdb1

Server Resources Used by X11 Clients: xrestop

xrestop provides statistics for each connected X11 client's server-side resource. The output is very similar to Section “Processes: top”.

xrestop - Display: localhost:0
          Monitoring 40 clients. XErrors: 0
          Pixmaps:   42013K total, Other:     206K total, All:   42219K total

res-base Wins  GCs Fnts Pxms Misc   Pxm mem  Other   Total   PID Identifier
3e00000   385   36    1  751  107    18161K     13K  18175K   ?   NOVELL: SU
4600000   391  122    1 1182  889     4566K     33K   4600K   ?   amaroK - S
1600000    35   11    0   76  142     3811K      4K   3816K   ?   KDE Deskto
3400000    52   31    1   69   74     2816K      4K   2820K   ?   Linux Shel
2c00000    50   25    1   43   50     2374K      3K   2378K   ?   Linux Shel
2e00000    50   10    1   36   42     2341K      3K   2344K   ?   Linux Shel
2600000    37   24    1   34   50     1772K      3K   1775K   ?   Root - Kon
4800000    37   24    1   34   49     1772K      3K   1775K   ?   Root - Kon
2a00000   209   33    1  323  238     1111K     12K   1123K   ?   Trekstor25
1800000   182   32    1  302  285     1039K     12K   1052K   ?   kicker
1400000   157  121    1  231  477      777K     18K    796K   ?   kwin
3c00000   175   36    1  248  168      510K      9K    520K   ?   de.comp.la
3a00000   326   42    1  579  444      486K     20K    506K   ?   [opensuse-
0a00000    85   38    1  317  224      102K      9K    111K   ?   Kopete
4e00000    25   17    1   60   66       63K      3K     66K   ?   YaST Contr
2400000    11   10    0   56   51       53K      1K     55K 22061 suseplugge
0e00000    20   12    1   50   92       50K      3K     54K 22016 kded
3200000     6   41    5   72   84       40K      8K     48K   ?   EMACS
2200000    54    9    1   30   31       42K      3K     45K   ?   SUSEWatche
4400000     2   11    1   30   34       34K      2K     36K 16489 kdesu
1a00000   255    7    0   42   11       19K      6K     26K   ?   KMix
3800000     2   14    1   34   37       21K      2K     24K 22242 knotify
1e00000    10    7    0   42    9       15K    624B     15K   ?   KPowersave
3600000   106    6    1   30    9        7K      3K     11K 22236 konqueror
2000000    10    5    0   21   34        9K      1K     10K   ?   klipper
3000000    21    7    0   11    9        7K    888B      8K   ?   KDE Wallet

User Information

Who Is Doing What: w

With the command w, find out who is logged onto the system and what each user is doing. For example:

tux@mercury:~> w
 14:58:43 up 1 day,  1:21,  2 users,  load average: 0.00, 0.00, 0.00
USER     TTY        LOGIN@   IDLE   JCPU   PCPU WHAT
tux      :0        12:25   ?xdm?   1:23   0.12s /bin/sh /usr/bin/startkde
root     pts/4     14:13    0.00s  0.06s  0.00s w

If any users of other systems have logged in remotely, the parameter -f shows the computers from which they have established the connection.

Time and Date

Time Measurement with time

Determine the time spent by commands with the time utility. This utility is available in two versions: as a shell built-in and as a program (/usr/bin/time).

tux@mercury:~> time find . > /dev/null

real    0m4.051s
user    0m0.042s
sys     0m0.205s

Chapter 14. Upgrading the System and System Changes

Abstract

You can upgrade an existing system without completely reinstalling it. There are two types of renewing the system or parts of it: updating individual software packages and upgrading the entire system. Updating individual packages is covered in Chapter 3, Installing or Removing Software and Chapter 4, YaST Online Update. Two ways to upgrade the system are discussed in the following sections— see Section “Upgrading with YaST” and Section “Distribution Upgrade with zypper”.

Upgrading the System

Software tends to “grow” from version to version. Therefore, take a look at the available partition space with df before updating. If you suspect you are running short of disk space, secure your data before you update and repartition your system. There is no general rule regarding how much space each partition should have. Space requirements depend on your particular partitioning profile, the software selected, and the version numbers of the system.

Preparations

Before upgrading, copy the old configuration files to a separate medium (such as tape device, removable hard disk, or USB flash drive) to secure the data. This primarily applies to files stored in /etc as well as some of the directories and files in /var. You may also want to write the user data in /home (the HOME directories) to a backup medium. Back up this data as root. Only root has read permission for all local files.

Before starting your update, make note of the root partition. The command df / lists the device name of the root partition. In Example 14.1, “List with df -h”, the root partition to write down is /dev/sda3 (mounted as /).

Example 14.1. List with df -h

Filesystem     Size  Used Avail Use% Mounted on
/dev/sda3       74G   22G   53G  29% /
udev           252M  124K  252M   1% /dev
/dev/sda5      116G  5.8G  111G   5% /home
/dev/sda1       39G  1.6G   37G   4% /windows/C
/dev/sda2      4.6G  2.6G  2.1G  57% /windows/D

Possible Problems

If you upgrade a default system from the previous version to this version, YaST works out the necessary changes and performs them. Depending on your customizations, some steps (or the entire upgrade procedure) may fail and you must resort to copying back your backup data. Here, we point out more issues to check before starting the system upgrade.

Checking passwd and group in /etc

Before upgrading the system, make sure that /etc/passwd and /etc/group do not contain any syntax errors. For this purpose, start the verification utilities pwck and grpck as root to eliminate any reported errors.

PostgreSQL

Before updating PostgreSQL (postgres), dump the databases. See the manual page of pg_dump. This is only necessary if you actually used PostgreSQL prior to your update.

Upgrading with YaST

Following the preparation procedure outlined in Section “Preparations”, you can now upgrade your system:

Boot the system as for the installation, described in “System Start-Up for Installation” (Chapter “Installation with YaST”, ↑Start-Up). In YaST, choose a language and select Update in the Installation Mode dialog. Do not select New Installation. Also add repositories to make sure to get all available software updated whenever possible. Find more information about installation repositories in “Add-On Products” (Chapter “Installation with YaST”, ↑Start-Up).

YaST determines if there are multiple root partitions. If there is only one, continue with the next step. If there are several, select the right partition and confirm with Next (/dev/sda3 was selected in the example in Section “Preparations”). YaST reads the old fstab on this partition to analyze and mount the file systems listed there.

Check the previously used repositories, if there are any. Enable all the repositories you still want to use and from where you want to update third-party software. Click the Toggle Status for every list item, if appropriate.

If you added repositories during the upgrade procedure as recommended above, you now can activate those you are actually interested in.

In the Installation Settings dialog, adjust the settings according to your requirements. Normally, you can leave the default settings untouched. If you intend to enhance your system, however, check the packages offered in the Software Selection submenus, or add support for additional languages.

You also have the possibility to make backups of various system components. Selecting backups slows down the upgrade process. Use this option if you do not have a recent system backup.

Confirm the upgrade by clicking Start Update.

Once the basic upgrade installation is finished, test the Internet connection as offered by the YaST dialog. Finally, YaST updates the remaining software and displays the release notes. Click Finish to write the YaST configuration.

Distribution Upgrade with zypper

With the zypper command line utility you can upgrade to the next version of your distribution. Most importantly, you can initiate the system upgrade process from within the running system.

This is attractive for advanced users who want to run remote upgrades or upgrades on many similarly configured systems. Inexperienced users will prefer the upgrade with YaST.

Before Starting the Upgrade with zypper

To avoid unexpected errors during the upgrade process using zypper, minimize risky constellations.

Upgrade from the previous version (e.g., 11.1) to this version (11.2)—do not skip any minor version inbetween (this means, do not upgrade from 11.0 or earlier to 11.2 in one go). Make sure all available 11.1 online updates are successfully applied.

Close as many applications and unneeded services as possible and log out all regular users.

Disable third party or openSUSE Build Service repositories before starting the upgrade, or lower the priority of these repositories to make sure packages from the default system repositories will get preference. Enable them again after the upgrade and edit their version string to match the version number of the distribution of the upgraded running system.

For more information, see http://en.opensuse.org/Upgrade/11.2#Command_line.

The Upgrade Procedure

Check Your System Backup

Before acutally starting the procedure, check that your system backup is up-to-date and restorable. This is especially important because you must enter many of the following steps manually.

Run the online update to make sure the software management stack is up-to-date. For more information, see Chapter 4, YaST Online Update.

Configure the repositories you want to use as an update source. To get this right is essential. Either use YaST (see Section “Managing Software Repositories and Services”) or zypper (see Section “Using Zypper”).

To view your current repositories enter:

zypper lr -u

Increase the version number of the system repositories from 11.1 to 11.2; add the new 11.2 repositories with commands such as:

server=http://download.opensuse.org
zypper ar $server/distribution/11.2/repo/oss/ openSUSE-11.2-Oss
zypper ar $server/update/11.2/ openSUSE-11.2-Update

And remove the old repositories:

zypper rr openSUSE-11.1-Oss
zypper rr openSUSE-11.1-Update

Disable third party repositories or other openSUSE Build Service repositories, because zypper dup is in test and guaranteed to work only with the default repositories:

zypper mr -d repo-alias

Conversely, you can lower the priority of these repositories.

Handling of Unresolved Dependencies

zypper dup will remove all packages having unresolved dependencies, but it keeps packages of disabled repositories as long as their dependencies are satisfied.

zypper dup ensures that all installed packages come from one of the available repositories. It does not consider the version, architecture, or vendor of the installed packages; thus it emulates a fresh installation. Packages that are no longer available in the repositories are considered orphaned. Such packages get uninstalled if their dependencies can not be satisfied. If they can be satisfied, such packages stay installed.

Once done, check your repository configuration with:

zypper lr -d

Refresh local metadata and repository contents with zypper ref.

Pull in zypper from the 11.2 repository with zypper in zypper.

Run the actual distribution upgrade with zypper dup. You are asked to confirm the license.

Perform basic system configuration with SuSEconfig.

Reboot the system with shutdown -r now.

Updating Individual Packages

Regardless of your overall updated environment, you can always update individual packages. From this point on, however, it is your responsibility to ensure that your system remains consistent. Update advice can be found at http://www.novell.com/linux/download/updates/.

Select components from the YaST package selection list according to your needs. If you select a package essential for the overall operation of the system, YaST issues a warning. Such packages should be updated only in the update mode. For example, many packages contain shared libraries. Updating these programs and applications in the running system may lead to system instability.

Software Changes from Version to Version

The individual modifications from version to version are outlined in the following in detail. This summary indicates, for example, whether basic settings have been completely reconfigured, configuration files have been moved to other places, or common applications have been significantly changed. Significant modifications that affect the daily use of the system at either the user level or the administrator level are mentioned here.

Problems and special issues of the various versions are published online as they are identified. See the links listed below. Important updates of individual packages can be accessed at http://www.novell.com/products/linuxprofessional/downloads/ using the YaST Online Update. For more information, see Chapter 4, YaST Online Update.

From 10.2 to 10.3

Refer to the Bugs article in the openSUSE wiki at http://en.opensuse.org/Bugs.

Text Installation Pattern

The scope of the text installation pattern is very limited. It is not recommended to install this pattern without adding additional software. Add packages from other patterns. The purpose of this pattern is to have a minimal bootable system running on real hardware. It provides a multiuser system with local login, network setup, and default filesystems. No service is enabled by default and the only YaST modules installed are those needed during installation.

Adding Extra Software Repositories During Installation

After setting up the update configuration at the end of the installation, YaST offers to add the following three software repositories as additional installation sources:

The “oss” repository contains the complete FTP distribution, including more packages than available on the CDs.

The “non-oss” repository contains software under a propietary or non-open source license.

The “debug” repository contains debuginfo packages used for debugging programs and libraries and getting backtraces. If an error occurs, this additional information helps you write good bug reports.

The source RPMs for “oss” are available at http://download.opensuse.org/distribution/10.3/src-oss, the source RPMs for “non-oss” are available at http://download.opensuse.org/distribution/10.3/src-non-oss.

Localization Support

The 1-CD installation media (GNOME or KDE) comes with language support for American English only.

Support for all the other languages is available separately. If you are interested in additional languages, add an extra online repository during installation which offers these translations. The “oss” repository, mentioned above in Section “Adding Extra Software Repositories During Installation”, is such a repository.

AppArmor 2.1

Find more detailed information about new features at http://en.opensuse.org/AppArmor/Changes_AppArmor_2_1.

The syntax now distinguishes directories from files. There are additional minor syntax bug fixes.

The reporting of change_hat related events and information has changed. The log messages and profile state (as available via /proc/<pid>/attr/current) are reported as /profile//hat.

A new change_profile policy specification has been added. change_profile is similar to change_hat, but allows changing to any profile, including hats. The profiles to which you can change must be specified. That is the only restriction. To change to a hat via change_profile, the hat name hsa to be specified by separating the profile and hat_name with // .

GAIM Renamed to Pidgin

The GAIM instant messenger has been renamed to Pidgin.

New Location for KDE and GNOME

GNOME 2 is installed under the /usr file system hierarchy since openSUSE 10.3 and KDE 4 now follows. KDE 3 will stay in /opt for compatibility reasons.

Before starting the update, make sure that there is enough disk space under /usr (approx. 2.5GB for both desktops is required). If you are short on space under /usr, resize or rearrange your partitions.

Berkeley DB Change Affects OpenLDAP Server

There is a format change in Berkeley DB's on-disk log files between Berkely DB 4.3 and 4.4. This change prevents an installed OpenLDAP server from starting after the system update.

To avoid this issue, export existing LDAP Databases using the slapcat utility before starting the system update and re-import the data using slapadd after the update. On an already-updated machine, get the LDAP Server running as follows:

Stop the LDAP Server.

Remove all files starting with _db. from the database directory.

Start the LDAP server again.

libata for IDE Devices

libata uses /dev/sda for the first hard disk, instead of /dev/hda. At present, disks with more than 15 partitions are not handled automatically. You can disable libata support by booting with the following kernel parameter:

hwprobe=-modules.pata

Now you see all the partitions over 15 again and can access them for installation.

Changes in Setting up Encrypted Partitions

The back-end technology of boot.crypto has been changed from cryptoloop to dm-crypt.

Any old /etc/cryptotab will work unmodified on openSUSE 10.3 (modulo partition renaming issues from hdX to sdX due to libata changes—see Section “libata for IDE Devices”). Additionally, /etc/crypttab (note the missing o) is now supported, which also includes support for LUKS volumes. In contrast to previous releases, boot.crypto is no longer enabled by default. YaST enables it if you create an encrypted volume with YaST. You can also manually enable it with the following command:

chkconfig boot.crypto on

It is still possible to use cryptoloop via losetup and mount. Since we dropped the crude loop-AES patch from the util-linux package, some parameters for losetup (such as itercountk and pseed) no longer exist. If any of these settings are used in /etc/fstab, the device cannot be mounted directly any more. Migrate these settings to /etc/crypttab where boot.crypto contains the necessary compatability code.

Enabling Quota Support

You now can configure quota for user accounts from within YaST. To enable quota support activate the Enable Quota Support check box in the fstab options when partitioning in the first stage of the installation. Thus, ensure that the /etc/init.d/boot.quota script is executed at boot time. In the second stage, the advanced options for user accounts provide the quota module where quota rules can be set.

If you enable quota support in the partitioner in the running system after installation, either reboot the system or manually remount the partitions concerned and execute the following command as root:

/etc/init.d/boot.quota restart

Zeroconf

The Zeroconf service (also known as Bonjour, Multicast DNS, mDNS, or DNS-SD) is now provided by the Avahi stack instead of mDNSResponder. However, mDNSResponder and howl compatibility libraries are still available.

To enable mDNS for all network interfaces, use the Zeroconf/Bonjour Multicast DNS SuSEFirewall2 rule.

Older Intel Graphics Chips

Older Intel graphics chips are supported by two drivers: i810 and intel. Due to the high demand for features like native mode setting (no longer VESA BIOS based) and RANDR 1.2 support, the intel driver is the default on openSUSE 10.3.

When updating to openSUSE 10.3, the i810 driver is not exchanged with the intel driver. Use the sax2 -r command to switch to the intel driver.

The intel driver is still not as stable as i810. Use the sax2 -r -m 0=i810 command to switch back to i810, if you encounter problems that did not occur previously with the i810 driver. In those cases, consider to opening a bug report concerning the intel driver.

Intel Wireless Link WiFi Drivers

Two drivers are available now: the traditional ipw3945 driver, which is installed by default, and the new iwlwifi driver as an alternative. Note the following caveats:

ipw3945 works on hidden networks. It does not survive suspend/resume cycles.

iwlwifi does not work on hidden networks. It supports suspend/resume cycles.

You can change the default using YaST. Click Software+Software Management and remove the ipw3945d package. The alternate iwlwifi driver is selected automatically for installation.

Tools to Write Optical Disc Media (CD-ROM and DVD)

The cdrecord package has been dropped from the distribution. The new wodim, genisoimage, and icedax packages from the cdrkit project can be used to record data or audio CDs on a CD recorder that conforms with the Orange Book standard. The following binaries have been renamed:

cdrecord to wodim

readcd to readom

mkisofs to genisoimage

cdda2wav to icedax

If your application relies on the old names, install the cdrkit-cdrtools-compat package. However, it would be appropriate to have native support for wodim in all front-end applications, because it offers some improvements:

The preferred way of specifying a device is dev=/dev/cdrecorder, dev=/dev/hdc, dev=/dev/sr0, etc.

Available devices can be listed with wodim -devices.

Suid root is not needed.

If you maintain such a front-end or script, consider adding native wodim support.

Use growisofs for writing DVDs. The graphical front-ends handle this transparently.

KDE 4 Applications Path

If you did not install the KDE desktop during the initial openSUSE 10.3 installation, install the KDE Base System and KDE 4 Base System patterns later. The KDE 4 application path is used as default. If you launch a KDE application such as Konqueror, the KDE 4 version of Konqueror loads instead of the KDE 3 version.

Playing MP3 Files in Kaffeine

When you open an MP3 file in Kaffeine, you will see an error message telling you that the software required to play this file is not installed. openSUSE then offers to search for a suitable codec which you can install with YaST. You can also switch the engine from Xine to Gstreamer by clicking Settings+Player Engine, getting MP3 support.

From 10.3 to 11.0

Refer to the Bugs article in the openSUSE wiki at http://en.opensuse.org/Bugs.

Press Ctrl-Alt-Backspace Twice to Terminate the X Server

Pressing Ctrl-Alt-Backspace on GNOME, KDE, or any other graphical desktop no longer terminates the X server. If you press Ctrl-Alt-Backspace within 2 seconds again, it terminates the X server. On most hardware you hear a beep after the first Ctrl-Alt-Backspace press.

In the past it was possible to accidentally terminate an X server using this key combination. Nevertheless, if you want to continue to use this key combination to terminate your X server, remove the following line from the ServerFlags section of the /etc/X11/xorg.conf file:

Option "ZapWarning" "on"

For more information, see the xorg.conf manpage.

YaST Gtk and Qt Front-Ends

By default, the new YaST gtk front-end runs on the GNOME desktop, and the YaST qt front-end on all the other desktops. Feature-wise, the gtk front-end is very similar to the qt front-end described in the manuals.

An exception is the gtk software management module (see the Start-Up guide in Chapter 3), which differs considerably from the qt port. To start the qt flavor on the GNOME desktop, invoke it as root at the command-line with:

yast2 --qt

Vice versa on KDE, if you are interested in the gtk front-end:

yast2 --gtk

Squid 3.0

Squid 3.0 is now available. This version supports the Internet Content Adaptation Protocol (ICAP) and Edge Side Includes (ESI).

Check your /etc/squid/squid.conf manually— that is only required after an update. For example, after the update proceed as follows:

cp /etc/squid/squid.conf /etc/squid/squid.conf.2.6
cp /etc/squid/squid.conf.rpmnew /etc/squid/squid.conf

Then transfer settings done for version 2.6 from /etc/squid/squid.conf.2.6 to /etc/squid/squid.conf. For reference, /etc/squid/squid.conf.default, which comes with squid 3.0, is also available.

Note the following changes:

changes in logging file access.log

squid.conf has new, renamed, and removed configuration options.

Features not available any longer:

  • refresh_stale_hit option. Not yet ported.
  • ability to follow X-Forwarded-For. Not yet ported.
  • Full caching of Vary/ETag using If-None-Match. Only basic Vary cache
    supported. Not yet ported.
  • Mapping of server error messages. Not yet ported.
  • http_access2 access directive. Not yet ported.
  • Location header rewrites. Not yet ported.
  • umask directive. Not yet ported.
  • wais_relay. Feature dropped as it's equivalent to cache_peer +
    cache_peer_access.
  • urlgroup. Not yet ported.
  • collapsed forwarding. Not yet ported.

For more information, see file:/usr/share/doc/packages/squid3/RELEASENOTES.html after package installation.

Xgl Versus AIGLX

On openSUSE 11.0 it is no longer possible to enable or disable Xgl with a graphical tool (such as with gnome-xgl-settings in the past). Only with the command line tool xgl-switch can you do this. Instead AIGLX is now always enabled on supported hardware. There are still some issues with AIGLX (e.g., Xvideo is usually slower, OpenGL applications are misplaced when you rotate compiz' cube), but the majority of our customers are requesting to have AIGLX enabled by default. If you prefer Xgl over AIGLX, use the command line tool xgl-switch to enable it:

xgl-switch --enable-xgl

If there are problems after enabling it (Xserver crashes, etc.) disable it again by running

xgl-switch --disable-xgl

The proprietary NVIDIA driver needs neither AIGLX nor Xgl for running with compositing managers, as it provides its own framework.

To enable Compiz, use the "Desktop Effects (simple-ccsm)" application from the application menu.

RPM Packages Now LZMA Compressed

RPM Packages in openSUSE 11.0 are now LZMA-compressed. LZMA provides a better compression rate and is faster on decompression.

The rpm packager in openSUSE 10.3 and earlier cannot handle such RPM packages. If you want to open or install LZMA-compressed RPMs on 10.3, install the rpm packager from 11.0 on your 10.3 system first. Note, this is not supported by Novell.

As a packager, remember to build packages for 10.3 (and earlier) without LZMA compression. Do not expect the user to install a new rpm packager on old systems.

Printing Legacy Encoded Text Files

The printing system based on CUPS 1.3.x (Common UNIX Printing System) no longer converts legacy encoded text files such as ISO-8859-1, windows-1252, and Asian encodings on its own. Only UTF-8 (and thus ASCII) is supported.

As a work-around to print legacy-encoded text files, convert before sending them to the CUPS server. To print an ISO-8859-1 text file, use:

iconv -f iso-8859-1 -t utf-8 filename.txt | lp -d printer

Note, the printing of PDF or PS or such binary files (JPEG, PNG, etc.) works as before.

CUPS (Common UNIX Printing System) and UTF-8 Encoding

Since CUPS 1.3.4 the cupsd accepts only UTF-8 encoded data. Because this change is not backward compatible, older CUPS clients such as CUPS 1.1 may no longer work. For an example, see http://www.cups.org/newsgroups.php?gcups.general+T+Q%22unsupported+charset%22.

Applications communicating with the cupsd (such as hp-setup or the YaST printer configuration) only work if either a plain 7-bit ASCII or a UTF-8 locale is used. The problem does not occur if you use a default UTF-8 locale, as has been pre-configured on openSUSE for several years.

Major Update of dhcpcd (1.x to 3.x)

A major update of the dhcpcd package (from 1.x to 3.x) is available. Command line options are different. For a complete list check the dhcpcd manpage and the /usr/share/doc/packages/dhcpcd/dhcpcd-1-vs-3 file.

Inode Size on the Ext3 Filesystem Increased

The inode size on the ext3 filesystem is increased from 128 to 256 by default. This change breaks many existing ext3 tools such as the windows tool EXTFS.

If you depend on such tools, install openSUSE with the old value.

SuSEfirewall2: New Variables Starting with FW_SERVICES_ACCEPT_RELATED_

SuSEfirewall2 implements a subtle change regarding packets that are considered RELATED by netfilter.

For example, to allow finer grained filtering of Samba broadcast packets, RELATED packets are no longer accepted unconditionally. New variables starting with FW_SERVICES_ACCEPT_RELATED_ have been introduced to allow restricting RELATED packet handling to certain networks, protocols and ports.

This means adding connection tracking modules (conntrack modules) to FW_LOAD_MODULES no longer automatically results in accepting the packets tagged by those modules. Additionally, you must set variables starting with FW_SERVICES_ACCEPT_RELATED_ to a suitable value.

Fingerprint Reader Devices and Encrypted Home Directories

If you want to use a fingerprint reader device, you must not encrypt the home directory. Otherwise logging in will fail, because decrypting during login is not possible in combination with an active fingerprint reader device.

To work around this limitation, set up a separate directory outside of the home directory and encrypt it manually.

TabletPC Configuration: xsetwacom Parameters

Use the following xsetwacom Parameters now:

For normal orientation (0° rotation):

xrandr -o 0 && xsetwacom set "Mouse[7]" RotateNONE

For 90° rotation (clockwise, portrait):

xrandr -o 3 && xsetwacom set "Mouse[7]" Rotate CW

For 180° rotation (landscape):

 xrandr -o 2 && xsetwacom set "Mouse[7]" Rotate HALF

For 270° rotation (counterclockwise, portrait):

 xrandr -o 1 && xsetwacom set "Mouse[7]" Rotate CCW

New On-Disk Format of sysstat

The new features of the sysstat package coming with 11.0 require a changed on-disk format of the data files. After the update of the sysstat package old collected data cannot be used.

From 11.0 to 11.1

Refer to the Bugs article in the openSUSE wiki at http://en.opensuse.org/Bugs.

Unable to Detect Display with Lid Closed

During the installation, YaST attempts to detect displays and determine the display size and resolution. If you are installing on a notebook with the lid closed, it is not be possible to detect the display. To avoid this problem, keep the lid open during installation.

If detection fails, start YaST and click "Hardware" -> "Graphics Card and Monitor". Then configure the display manually.

Detecting Lenovo ThinkPad Laptops

Lenovo ThinkPad laptops have special code in the MBR (master boot record) because of the "Blue ThinkVantage button" functionality. If detecting and preparing it fails, it might be necessary to restore the boot sector.

If you have a ThinkPad, ensure that the bootloader is not installed into the MBR (verify it in the installation proposal!) and the MBR is not rewritten by generic code (in installation proposal select Bootloader -> Boot Loader Installation -> Boot Loader Options -> Write Generic Boot Code to MBR -- should be unchecked).

If your MBR gets rewritten, the ThinkVantage button will not work anymore. The back-up of the MBR is stored in /var/lib/YaST2/backup_boot_sectors/.

XEN Configuration

Updating from openSUSE 11.0 to openSUSE 11.1 with the Xen Hypervisor may have an incorrect network configuration, because the update does not configure the bridged setup automatically.

Start the "YaST Control Center", choose "Virtualization" and then "Install Hypervisor and Tools" to start the bridge proposal for networking. Conversely, you can call "yast2 xen" on the commandline.

Note, if you install openSUSE 11.1 and configure Xen, you get a bridged setup through YaST automatically.

Displaying Man-Pages With the Same Name

The man command now asks which man-page the user wants to see if man-pages with the same name exist in different sections. The user is expected to type the section number to make this man-page visible.

If you want to get back the previous behavior, set MAN_POSIXLY_CORRECT=1 in a shell initialization file such as ~/.bashrc.

YaST LDAP Server Configuration

The YaST LDAP Server module does not store the LDAP Server configuration in /etc/openldap/slapd.conf any longer. The module now uses OpenLDAP's dynamic configuration backend, which stores the configuration in an LDAP database itself. That database consists of a set of .ldif files in /etc/openldap/slapd.d. To access the configuration either use the yast2-ldap-server module or an LDAP client such as ldapmodify or ldapsearch.

For details on the dymanic configuration of OpenLDAP, see the OpenLDAP Administration Guide.

Configuring Network Connections

By default, Network Manager is enabled and manages network connections. If you want configure it, you must use a Network Manager applet to change the settings. As long as Network Manager is running, YaST refuses to configure the network settings, because YaST and Network Manager have different sets of configuration options.

netconfig Utility to Apply Additional Network Settings

The modify_resolvconf script is removed in favor of the more versatile netconfig script. The new script handles specific network settings from multiple sources more flexibly and transparently. For more information, see the updated manuals and the netconfig man-page.

In the shipped manuals, modify_resolvconf is erroneously referenced. We will correct it in the next release.

WLAN Channels 12, 13, and 14 Disabled

By default, the WLAN channels 12, 13, and 14 are disabled because it is not allowed to use these channels everywhere. If you want to use them in your region, see http://en.opensuse.org/Tracking_down_wireless_problems for more information.

The command-not-found Script

On the command line, if you enter a command that could not be found, bash and zsh call the /usr/bin/command-not-found handler. command-not-found then searches a package database and proposes how to proceed.

If you want to disable this behavior, either remove the command-not-found package or unset command_not_found_handle in your shell initialization file. For example, add to ~/.bashrc:

unset command_not_found_handle

From 11.1 to 11.2

Refer to the Bugs article in the openSUSE wiki at http://en.opensuse.org/Bugs.

Part IV. System

Chapter 15. 32-Bit and 64-Bit Applications in a 64-Bit System Environment

openSUSE® is available for 64-bit platforms. This does not necessarily mean that all the applications included have already been ported to 64-bit platforms. openSUSE supports the use of 32-bit applications in a 64-bit system environment. This chapter offers a brief overview of how this support is implemented on 64-bit openSUSE platforms. It explains how 32-bit applications are executed (runtime support) and how 32-bit applications should be compiled to enable them to run both in 32-bit and 64-bit system environments. Additionally, find information about the kernel API and an explanation of how 32-bit applications can run under a 64-bit kernel.

openSUSE for the 64-bit platforms amd64 and Intel 64 is designed so that existing 32-bit applications run in the 64-bit environment “out-of-the-box.” This support means that you can continue to use your preferred 32-bit applications without waiting for a corresponding 64-bit port to become available.

Runtime Support

Conflicts between Application Versions

If an application is available both for 32-bit and 64-bit environments, parallel installation of both versions is bound to lead to problems. In such cases, decide on one of the two versions and install and use this.

An exception to this rule is PAM (pluggable authentication modules). openSUSE uses PAM in the authentication process as a layer that mediates between user and application. On a 64-Bit operating system that also runs 32-Bit applications it is necessary to always install both versions of a PAM module.

To be executed correctly, every application requires a range of libraries. Unfortunately, the names for the 32-bit and 64-bit versions of these libraries are identical. They must be differentiated from each other in another way.

To retain compatibility with the 32-bit version, the libraries are stored at the same place in the system as in the 32-bit environment. The 32-bit version of libc.so.6 is located under /lib/libc.so.6 in both the 32-bit and 64-bit environments.

All 64-bit libraries and object files are located in directories called lib64. The 64-bit object files you would normally expect to find under /lib and /usr/lib are now found under /lib64 and /usr/lib64. This means that there is space for the 32-bit libraries under /lib and /usr/lib, so the filename for both versions can remain unchanged.

Subdirectories of 32-bit /lib directories which contain data content that does not depend on the word size are not moved. This scheme conforms to LSB (Linux Standards Base) and FHS (File System Hierarchy Standard).

Software Development

A biarch development tool chain allows generation of 32-bit and 64-bit objects. The default is to compile 64-bit objects. It is possible to generate 32-bit objects by using special flags. For GCC, this special flag is -m32.

All header files must be written in an architecture-independent form. The installed 32-bit and 64-bit libraries must have an API (application programming interface) that matches the installed header files. The normal openSUSE environment is designed according to this principle. In the case of manually updated libraries, resolve these issues yourself.

Software Compilation on Biarch Platforms

To develop binaries for the other architecture on a biarch architecture, the respective libraries for the second architecture must additionally be installed. These packages are called rpmname-32bit. You also need the respective headers and libraries from the rpmname-devel packages and the development libraries for the second architecture from rpmname-devel-32bit.

Most open source programs use an autoconf-based program configuration. To use autoconf for configuring a program for the second architecture, overwrite the normal compiler and linker settings of autoconf by running the configure script with additional environment variables.

The following example refers to an x86_64 system with x86 as the second architecture.

Use the 32-bit compiler:

CC="gcc -m32"

Instruct the linker to process 32-bit objects (always use gcc as the linker front-end):

LD="gcc -m32"

Set the assembler to generate 32-bit objects:

AS="gcc -c -m32"

Determine that the libraries for libtool and so on come from /usr/lib:

LDFLAGS="-L/usr/lib"

Determine that the libraries are stored in the lib subdirectory:

--libdir=/usr/lib

Determine that the 32-bit X libraries are used:

--x-libraries=/usr/lib/xorg

Not all of these variables are needed for every program. Adapt them to the respective program.

CC="gcc -m32"            \
LDFLAGS="-L/usr/lib;"  \
        .configure       \
          --prefix=/usr  \
          --libdir=/usr/lib
make
make install

Kernel Specifications

The 64-bit kernels for x86_64 offer both a 64-bit and a 32-bit kernel ABI (application binary interface). The latter is identical with the ABI for the corresponding 32-bit kernel. This means that the 32-bit application can communicate with the 64-bit kernel in the same way as with the 32-bit kernel.

The 32-bit emulation of system calls for a 64-bit kernel does not support all the APIs used by system programs. This depends on the platform. For this reason, a small number of applications, like lspci, must be compiled

A 64-bit kernel can only load 64-bit kernel modules that have been specially compiled for this kernel. It is not possible to use 32-bit kernel modules.

Tip

Some applications require separate kernel-loadable modules. If you intend to use such a 32-bit application in a 64-bit system environment, contact the provider of this application and Novell to make sure that the 64-bit version of the kernel-loadable module and the 32-bit compiled version of the kernel API are available for this module.

Chapter 16. Booting and Configuring a Linux System

Abstract

Booting a Linux system involves different components. The hardware itself is initialized by the BIOS, which starts the kernel by means of a boot loader. After this point, the boot process with init and the runlevels is completely controlled by the operating system. The runlevel concept enables you to maintain setups for everyday usage as well as to perform maintenance tasks on the system.

The Linux Boot Process

The Linux boot process consists of several stages, each represented by a different component. The following list briefly summarizes the boot process and features all the major components involved.

BIOS.  After turning on the computer, the BIOS initializes the screen and keyboard and tests the main memory. Up to this stage, the machine does not access any mass storage media. Subsequently, the information about the current date, time, and the most important peripherals are loaded from the CMOS values. When the first hard disk and its geometry are recognized, the system control passes from the BIOS to the boot loader.

Boot Loader.  The first physical 512-byte data sector of the first hard disk is loaded into the main memory and the boot loader that resides at the beginning of this sector takes over. The commands executed by the boot loader determine the remaining part of the boot process. Therefore, the first 512 bytes on the first hard disk are referred to as the Master Boot Record (MBR). The boot loader then passes control to the actual operating system, in this case, the Linux kernel. More information about GRUB, the Linux boot loader, can be found in Chapter 17, The Boot Loader GRUB.

Kernel and initramfs.  To pass system control, the boot loader loads both the kernel and an initial RAM–based file system (initramfs) into memory. The contents of the initramfs can be used by the kernel directly. initramfs contains a small executable called init that handles the mounting of the real root file system. If special hardware drivers are needed before the mass storage can be accessed, they must be in initramfs. For more information about initramfs, refer to Section “initramfs”.

init on initramfs.  This program performs all actions needed to mount the proper root file system, like providing kernel functionality for the needed file system and device drivers for mass storage controllers with udev. After the root file system has been found, it is checked for errors and mounted. If this is successful, the initramfs is cleaned and the init program on the root file system is executed. For more information about init, refer to Section “init on initramfs”. Find more information about udev in Chapter 19, Dynamic Kernel Device Management with udev.

init.  init handles the actual booting of the system through several different levels providing different functionality. init is described in Section “The init Process”.

initramfs

initramfs is a small cpio archive that the kernel can load to a RAM disk. It provides a minimal Linux environment that enables the execution of programs before the actual root file system is mounted. This minimal Linux environment is loaded into memory by BIOS routines and does not have specific hardware requirements other than sufficient memory. initramfs must always provide an executable named init that should execute the actual init program on the root file system for the boot process to proceed.

Before the root file system can be mounted and the operating system can be started, the kernel needs the corresponding drivers to access the device on which the root file system is located. These drivers may include special drivers for certain kinds of hard drives or even network drivers to access a network file system. The needed modules for the root file system may be loaded by init on initramfs. After the modules are loaded, udev provides the initramfs with the needed devices. Later in the boot process, after changing the root file system, it is necessary to regenerate the devices. This is done by boot.udev with the command udevtrigger.

If you need to change hardware (e.g. hard disks) in an installed system and this hardware requires different drivers to be present in the kernel at boot time, you must update initramfs. This is done in the same way as with its predecessor, initrd—by calling mkinitrd. Calling mkinitrd without any argument creates an initramfs. Calling mkinitrd -R creates an initrd. In openSUSE®, the modules to load are specified by the variable INITRD_MODULES in /etc/sysconfig/kernel. After installation, this variable is automatically set to the correct value. The modules are loaded in exactly the order in which they appear in INITRD_MODULES. This is only important if you rely on the correct setting of the device files /dev/sd?. However, in current systems you also may use the device files below /dev/disk/ that are sorted in several subdirectories, named by-id, by-path and by-uuid, and always represent the same disk. This is also possible at install time by specifying the respective mount option.

Updating initramfs or initrd

The boot loader loads initramfs or initrd in the same way as the kernel. It is not necessary to reinstall GRUB after updating initramfs or initrd, because GRUB searches the directory for the right file when booting.

init on initramfs

The main purpose of init on initramfs is to prepare the mounting of and access to the real root file system. Depending on your system configuration, init is responsible for the following tasks.

Loading Kernel Modules

Depending on your hardware configuration, special drivers may be needed to access the hardware components of your computer (the most important component being your hard drive). To access the final root file system, the kernel needs to load the proper file system drivers.

Providing Block Special Files

For each loaded module, the kernel generates device events. udev handles these events and generates the required block special files on a RAM file system in /dev. Without those special files, the file system and other devices would not be accessible.

Managing RAID and LVM Setups

If you configured your system to hold the root file system under RAID or LVM, init sets up LVM or RAID to enable access to the root file system later. Find information about RAID and LVM in Chapter 2, Advanced Disk Setup.

Managing Network Configuration

If you configured your system to use a network-mounted root file system (mounted via NFS), init must make sure that the proper network drivers are loaded and that they are set up to allow access to the root file system.

When init is called during the initial boot as part of the installation process, its tasks differ from those mentioned above:

Finding the Installation Medium

As you start the installation process, your machine loads an installation kernel and a special initrd with the YaST installer on the installation medium. The YaST installer, which is run in a RAM file system, needs to have information about the location of the installation medium to access it and install the operating system.

Initiating Hardware Recognition and Loading Appropriate Kernel Modules

As mentioned in Section “initramfs”, the boot process starts with a minimum set of drivers that can be used with most hardware configurations. init starts an initial hardware scanning process that determines the set of drivers suitable for your hardware configuration. The names of the modules needed for the boot process are written to INITRD_MODULES in /etc/sysconfig/kernel. These names are used to generate a custom initramfs that is needed to boot the system. If the modules are not needed for boot but for coldplug, the modules are written to /etc/sysconfig/hardware/hwconfig-*. All devices that are described with configuration files in this directory are initialized in the boot process.

Loading the Installation System or Rescue System

As soon as the hardware is properly recognized, the appropriate drivers are loaded, and udev creates the special device files, init starts the installation system with the actual YaST installer, or the rescue system.

Starting YaST

Finally, init starts YaST, which starts package installation and system configuration.

The init Process

The program init is the process with process ID 1. It is responsible for initializing the system in the required way. init is started directly by the kernel and resists signal 9, which normally kills processes. All other programs are either started directly by init or by one of its child processes.

init is centrally configured in the /etc/inittab file where the runlevels are defined (see Section “Runlevels”). The file also specifies which services and daemons are available in each of the runlevels. Depending on the entries in /etc/inittab, several scripts are run by init. By default, the first script that is started after booting is /etc/init.d/boot. Once the system initialization phase is finished, the system changes the runlevel to its default runlevel with the /etc/init.d/rc script. For reasons of clarity, these scripts, called init scripts, all reside in the directory /etc/init.d (see Section “Init Scripts”).

The entire process of starting the system and shutting it down is maintained by init. From this point of view, the kernel can be considered a background process to maintain all other processes and adjust CPU time and hardware access according to requests from other programs.

Runlevels

In Linux, runlevels define how the system is started and what services are available in the running system. After booting, the system starts as defined in /etc/inittab in the line initdefault. Usually this is 3 or 5. See Table 16.1, “Available Runlevels”. As an alternative, the runlevel can be specified at boot time (by adding the runlevel number at the boot prompt, for instance). Any parameters that are not directly evaluated by the kernel itself are passed to init. To boot into runlevel 3, just add a the single number 3 to the boot prompt.

Table 16.1. Available Runlevels

Runlevel

Description

0

System halt

S or 1

Single user mode

2

Local multiuser mode without remote network (NFS, etc.)

3

Full multiuser mode with network

4

User Defined, this is not used unless the administrator configures this runlevel.

5

Full multiuser mode with network and X display manager—KDM, GDM, or XDM

6

System reboot

Avoid Runlevel 2 with a Partition Mounted via NFS

You should not use runlevel 2 if your system mounts a partition like /usr via NFS. The system might behave unexpectedly if program files or libraries are missing because the NFS service is not available in runlevel 2 (local multiuser mode without remote network).

To change runlevels while the system is running, enter telinit and the corresponding number as an argument. Only the system administrator is allowed to do this. The following list summarizes the most important commands in the runlevel area.

telinit 1 or shutdown now

The system changes to single user mode. This mode is used for system maintenance and administration tasks.

telinit 3

All essential programs and services (including network) are started and regular users are allowed to log in and work with the system without a graphical environment.

telinit 5

The graphical environment is enabled. Usually a display manager like XDM, GDM or KDM is started. If autologin is enabled, the local user is logged in to the preselected window manager (GNOME or KDE or any other window manager).

telinit 0 or shutdown -h now

The system halts.

telinit 6 or shutdown -r now

The system halts then reboots.

Runlevel 5 is the default runlevel in all openSUSE standard installations. Users are prompted for login with a graphical interface or the default user is logged in automatically.

Errors in /etc/inittab May Result in a Faulty System Boot

If /etc/inittab is damaged, the system may not boot properly. Therefore, be extremely careful while editing /etc/inittab. Always let init reread /etc/inittab with the command telinit q before rebooting the machine.

Generally, two things happen when you change runlevels. First, stop scripts of the current runlevel are launched, closing down some programs essential for the current runlevel. Then start scripts of the new runlevel are started. Here, in most cases, a number of programs are started. For example, the following occurs when changing from runlevel 3 to 5:

The administrator (root) requests init to change to a different runlevel by entering telinit 5.

init checks the current runlevel (runlevel) and determines it should start /etc/init.d/rc with the new runlevel as a parameter.

Now rc calls the stop scripts of the current runlevel for which there is no start script in the new runlevel. In this example, these are all the scripts that reside in /etc/init.d/rc3.d (the old runlevel was 3) and start with a K. The number following K specifies the order to run the scripts with the stop parameter, because there are some dependencies to consider.

The last things to start are the start scripts of the new runlevel. In this example, these are in /etc/init.d/rc5.d and begin with an S. Again, the number that follows the S determines the sequence in which the scripts are started.

When changing into the same runlevel as the current runlevel, init only checks /etc/inittab for changes and starts the appropriate steps, for example, for starting a getty on another interface. The same functionality may be achieved with the command telinit q.

Init Scripts

There are two types of scripts in /etc/init.d:

Scripts Executed Directly by init

This is the case only during the boot process or if an immediate system shutdown is initiated (power failure or a user pressing Ctrl+Alt+Del). The execution of these scripts is defined in /etc/inittab.

Scripts Executed Indirectly by init

These are run when changing the runlevel and always call the master script /etc/init.d/rc, which guarantees the correct order of the relevant scripts.

All scripts are located in /etc/init.d. Scripts that are run at boot time are called through symbolic links from /etc/init.d/boot.d. Scripts for changing the runlevel are called through symbolic links from one of the subdirectories (/etc/init.d/rc0.d to /etc/init.d/rc6.d). This is just for reasons of clarity and avoids duplicate scripts if they are used in several runlevels. Because every script can be executed as both a start and a stop script, these scripts must understand the parameters start and stop. The scripts also understand the restart, reload, force-reload, and status options. These different options are explained in Table 16.2, “Possible init Script Options”. Scripts that are run directly by init do not have these links. They are run independently from the runlevel when needed.

Table 16.2. Possible init Script Options

Option

Description

start

Start service.

stop

Stop service.

restart

If the service is running, stop it then restart it. If it is not running, start it.

reload

Reload the configuration without stopping and restarting the service.

force-reload

Reload the configuration if the service supports this. Otherwise, do the same as if restart had been given.

status

Show the current status of service.

Links in each runlevel-specific subdirectory make it possible to associate scripts with different runlevels. When installing or uninstalling packages, these links are added and removed with the help of the program insserv (or using /usr/lib/lsb/install_initd, which is a script calling this program). See the insserv(8) man page for details.

All of these settings may also be changed with the help of the YaST module. If you need to check the status on the command line, use the tool chkconfig, described in the chkconfig(8) man page.

A short introduction to the boot and stop scripts launched first or last, respectively, follows as well as an explanation of the maintaining script.

boot

Executed while starting the system directly using init. It is independent of the chosen runlevel and is only executed once. Here, the /proc and /dev/pts file systems are mounted and blogd (boot logging daemon) is activated. If the system is booted for the first time after an update or an installation, the initial system configuration is started.

The blogd daemon is a service started by boot and rc before any other one. It is stopped after the actions triggered by these scripts (running a number of subscripts, for example, making block special files available) are completed. blogd writes any screen output to the log file /var/log/boot.msg, but only if and when /var is mounted read-write. Otherwise, blogd buffers all screen data until /var becomes available. Get further information about blogd on the blogd(8) man page.

The boot script is also responsible for starting all the scripts in /etc/init.d/boot.d with names that start with S. There, the file systems are checked and loop devices are configured if needed. The system time is also set. If an error occurs while automatically checking and repairing the file system, the system administrator can intervene after first entering the root password. The last executed script is boot.local.

boot.local

Here, enter additional commands to execute at boot before changing into a runlevel. It can be compared to AUTOEXEC.BAT on DOS systems.

halt

This script is only executed while changing into runlevel 0 or 6. Here, it is executed either as halt or as reboot. Whether the system shuts down or reboots depends on how halt is called. If special commands are needed during the shutdown, add these to the halt.local script.

rc

This script calls the appropriate stop scripts of the current runlevel and the start scripts of the newly selected runlevel. Like the /etc/init.d/boot script, this script is called from /etc/inittab with the desired runlevel as parameter.

You can create your own scripts and easily integrate them into the scheme described above. For instructions about formatting, naming and organizing custom scripts, refer to the specifications of the LSB and to the man pages of init, init.d, chkconfig, and insserv. Additionally consult the man pages of startproc and killproc.

Faulty init Scripts May Halt Your System

Faulty init scripts may hang your machine up. Edit such scripts with great care and, if possible, subject them to heavy testing in the multiuser environment. Find useful information about init scripts in Section “Runlevels”.

To create a custom init script for a given program or service, use the file /etc/init.d/skeleton as a template. Save a copy of this file under the new name and edit the relevant program and filenames, paths and other details as needed. You may also need to enhance the script with your own parts, so the correct actions are triggered by the init procedure.

The INIT INFO block at the top is a required part of the script and must be edited. See Example 16.1, “A Minimal INIT INFO Block”.

Example 16.1. A Minimal INIT INFO Block

### BEGIN INIT INFO
# Provides:          FOO
# Required-Start:    $syslog $remote_fs
# Required-Stop:     $syslog $remote_fs
# Default-Start:     3 5
# Default-Stop:      0 1 2 6
# Description:       Start FOO to allow XY and provide YZ
### END INIT INFO

In the first line of the INFO block, after Provides:, specify the name of the program or service controlled by this init script. In the Required-Start: and Required-Stop: lines, specify all services that need to be started or stopped before the service itself is started or stopped. This information is used later to generate the numbering of script names, as found in the runlevel directories. After Default-Start: and Default-Stop:, specify the runlevels in which the service should automatically be started or stopped. Finally, for Description:, provide a short description of the service in question.

To create the links from the runlevel directories (/etc/init.d/rc?.d/) to the corresponding scripts in /etc/init.d/, enter the command insserv new-script-name. The insserv program evaluates the INIT INFO header to create the necessary links for start and stop scripts in the runlevel directories (/etc/init.d/rc?.d/). The program also takes care of the correct start and stop order for each runlevel by including the necessary numbers in the names of these links. If you prefer a graphical tool to create such links, use the runlevel editor provided by YaST, as described in Section “Configuring System Services (Runlevel) with YaST”.

If a script already present in /etc/init.d/ should be integrated into the existing runlevel scheme, create the links in the runlevel directories right away with insserv or by enabling the corresponding service in the runlevel editor of YaST. Your changes are applied during the next reboot—the new service is started automatically.

Do not set these links manually. If something is wrong in the INFO block, problems will arise when insserv is run later for some other service. The manually-added service will be removed with the next run of insserv for this script.

Configuring System Services (Runlevel) with YaST

After starting this YaST module with YaST+System+System Services (Runlevel), it displays an overview listing all the available services and the current status of each service (disabled or enabled). Decide whether to use the module in Simple Mode or in Expert Mode. The default Simple Mode should be sufficient for most purposes. The left column shows the name of the service, the center column indicates its current status and the right column gives a short description. For the selected service, a more detailed description is provided in the lower part of the window. To enable a service, select it in the table then select Enable. The same steps apply to disable a service.

For detailed control over the runlevels in which a service is started or stopped or to change the default runlevel, first select Expert Mode. The current default runlevel or “initdefault” (the runlevel into which the system boots by default) is displayed at the top. Normally, the default runlevel of a openSUSE system is runlevel 5 (full multiuser mode with network and X). A suitable alternative might be runlevel 3 (full multiuser mode with network).

This YaST dialog allows the selection of one of the runlevels (as listed in Table 16.1, “Available Runlevels”) as the new default. Additionally, use the table in this window to enable or disable individual services and daemons. The table lists the services and daemons available, shows whether they are currently enabled on your system and, if so, for which runlevels. After selecting one of the rows with the mouse, click the check boxes representing the runlevels (B, 0, 1, 2, 3, 5, 6, and S) to define the runlevels in which the selected service or daemon should be running. Runlevel 4 is undefined to allow creation of a custom runlevel. A brief description of the currently selected service or daemon is provided below the table overview.

Faulty Runlevel Settings May Damage Your System

Faulty runlevel settings may make your system unusable. Before applying your changes, make absolutely sure that you know their consequences.

Figure 16.1. System Services (Runlevel)

With Start, Stop, or Refresh, decide whether a service should be activated. Refresh status checks the current status. Set or Reset lets you select whether to apply your changes to the system or to restore the settings that existed before starting the runlevel editor. Selecting Finish saves the changed settings to disk.

System Configuration via /etc/sysconfig

The main configuration of openSUSE is controlled by the configuration files in /etc/sysconfig. The individual files in /etc/sysconfig are only read by the scripts to which they are relevant. This ensures that network settings, for example, only need to be parsed by network-related scripts.

There are two ways to edit the system configuration. Either use the YaST sysconfig Editor or edit the configuration files manually.

Changing the System Configuration Using the YaST sysconfig Editor

The YaST sysconfig editor provides an easy-to-use front-end for system configuration. Without any knowledge of the actual location of the configuration variable you need to change, you can just use the built-in search function of this module, change the value of the configuration variable as needed and let YaST take care of applying these changes, updating configurations that depend on the values set in sysconfig and restarting services.

Modifying /etc/sysconfig/* Files Can Damage Your Installation

Do not modify the /etc/sysconfig files if you lack previous experience and knowledge. It could do considerable damage to your system. The files in /etc/sysconfig include a short comment for each variable to explain what effect they actually have.

Figure 16.2. System Configuration Using the sysconfig Editor

The YaST sysconfig dialog is split into three parts. The left part of the dialog shows a tree view of all configurable variables. When you select a variable, the right part displays both the current selection and the current setting of this variable. Below, a third window displays a short description of the variable's purpose, possible values, the default value and the actual configuration file from which this variable originates. The dialog also provides information about which configuration script is executed after changing the variable and which new service is started as a result of the change. YaST prompts you to confirm your changes and informs you which scripts will be executed after you leave the dialog by selecting Finish. Also select the services and scripts to skip for now, so they are started later. YaST applies all changes automatically and restarts any services involved for your changes to take an effect.

Changing the System Configuration Manually

To manually change the system configuration, proceed as follows

Become root.

Bring the system into single user mode (runlevel 1) with telinit 1.

Change the configuration files as needed with an editor of your choice.

If you do not use YaST to change the configuration files in /etc/sysconfig, make sure that empty variable values are represented by two quotation marks (KEYTABLE="") and that values with blanks in them are enclosed in quotation marks. Values consisting of one word only do not need to be quoted.

Execute SuSEconfig to make sure that the changes take effect.

Bring your system back to the previous runlevel with a command like telinit default_runlevel. Replace default_runlevel with the default runlevel of the system. Choose 5 if you want to return to full multiuser with network and X or choose 3 if you prefer to work in full multiuser with network.

This procedure is mainly relevant when changing systemwide settings, such as the network configuration. Small changes should not require going into single user mode, but you may still do so to make absolutely sure that all the programs concerned are correctly restarted.

Configuring Automated System Configuration

To disable the automated system configuration by SuSEconfig, set the variable ENABLE_SUSECONFIG in /etc/sysconfig/suseconfig to no. Do not disable SuSEconfig if you want to use the SUSE installation support. It is also possible to disable the autoconfiguration partially.

Chapter 17. The Boot Loader GRUB

Abstract

This chapter describes how to configure GRUB, the boot loader used in openSUSE®. A special YaST module is available for configuring all settings. If you are not familiar with the subject of booting in Linux, read the following sections to acquire some background information. This chapter also describes some of the problems frequently encountered when booting with GRUB and their solutions.

This chapter focuses on boot management and the configuration of the boot loader GRUB. The boot procedure as a whole is outlined in Chapter 16, Booting and Configuring a Linux System. A boot loader represents the interface between the machine (BIOS) and the operating system (openSUSE). The configuration of the boot loader directly impacts the start of the operating system.

The following terms appear frequently in this chapter and might need some explanation:

Master Boot Record

The structure of the MBR is defined by an operating system–independent convention. The first 446 bytes are reserved for the program code. They typically hold part of a boot loader program or an operating system selector. The next 64 bytes provide space for a partition table of up to four entries. The partition table contains information about the partitioning of the hard disk and the file system types. The operating system needs this table for handling the hard disk. With conventional generic code in the MBR, exactly one partition must be marked active. The last two bytes of the MBR must contain a static “magic number” (AA55). An MBR containing a different value is regarded as invalid by some BIOSes, so is not considered for booting.

Boot Sectors

Boot sectors are the first sectors of hard disk partitions with the exception of the extended partition, which merely serves as a “container” for other partitions. These boot sectors have 512 bytes of space for code used to boot an operating system installed in the respective partition. This applies to boot sectors of formatted DOS, Windows, and OS/2 partitions, which also contain some basic important data of the file system. In contrast, the boot sectors of Linux partitions are initially empty after setting up a file system other than XFS. Therefore, a Linux partition is not bootable by itself, even if it contains a kernel and a valid root file system. A boot sector with valid code for booting the system has the same magic number as the MBR in its last two bytes (AA55).

Booting with GRUB

GRUB (Grand Unified Bootloader) comprises two stages. Stage 1 consists of 512 bytes and its only task is to load the second stage of the boot loader. Subsequently, stage 2 is loaded. This stage contains the main part of the boot loader.

In some configurations, an intermediate stage 1.5 can be used, which locates and loads stage 2 from an appropriate file system. If possible, this method is chosen by default on installation or when initially setting up GRUB with YaST.

Stage 2 is able to access many file systems. Currently, Ext2, Ext3, ReiserFS, Minix, and the DOS FAT file system used by Windows are supported. To a certain extent, XFS, and UFS and FFS used by BSD systems are also supported. Since version 0.95 GRUB is also able to boot from a CD or DVD containing an ISO 9660 standard file system pursuant to the “El Torito” specification. Even before the system is booted, GRUB can access file systems of supported BIOS disk devices (floppy disks or hard disks, CD drives and DVD drives detected by the BIOS). Therefore, changes to the GRUB configuration file (menu.lst) do not require a new installation of the boot manager. When the system is booted, GRUB reloads the menu file with the valid paths and partition data of the kernel or the initial RAM disk (initrd) and locates these files.

The actual configuration of GRUB is based on four files that are described below:

/boot/grub/menu.lst

This file contains all information about partitions or operating systems that can be booted with GRUB. Without this information, the GRUB command line prompts the user for how to proceed (see Section “Editing Menu Entries during the Boot Procedure” for details).

/boot/grub/device.map

This file translates device names from the GRUB and BIOS notation to Linux device names.

/etc/grub.conf

This file contains the commands, parameters and options the GRUB shell needs for installing the boot loader correctly.

/etc/sysconfig/bootloader

This file is read by the perl-bootloader library which is used when configuring the bootloader with YaST and every time a new kernel is installed. It contains configuration options (such as kernel parameters) that will be added by default to the bootloader configuration file.

GRUB can be controlled in various ways. Boot entries from an existing configuration can be selected from the graphical menu (splash screen). The configuration is loaded from the file menu.lst.

In GRUB, all boot parameters can be changed prior to booting. For example, errors made when editing the menu file can be corrected in this way. Boot commands can also be entered interactively at a kind of input prompt (see Section “Editing Menu Entries during the Boot Procedure”). GRUB offers the possibility of determining the location of the kernel and the initrd prior to booting. In this way, you can even boot an installed operating system for which no entry exists in the boot loader configuration.

GRUB actually exists in two versions: as a boot loader and as a normal Linux program in /usr/sbin/grub. The latter is referred to as the GRUB shell. It provides an emulation of GRUB in the installed system and can be used to install GRUB or test new settings before applying them. The functionality to install GRUB as the boot loader on a hard disk or floppy disk is integrated in GRUB in the form of the command setup. This is available in the GRUB shell when Linux is loaded.

The File /boot/grub/menu.lst

The graphical splash screen with the boot menu is based on the GRUB configuration file /boot/grub/menu.lst, which contains all information about all partitions or operating systems that can be booted by the menu.

Every time the system is booted, GRUB loads the menu file from the file system. For this reason, GRUB does not need to be reinstalled after every change to the file. Use the YaST boot loader to modify the GRUB configuration as described in Section “Configuring the Boot Loader with YaST”.

The menu file contains commands. The syntax is very simple. Every line contains a command followed by optional parameters separated by spaces like in the shell. For historical reasons, some commands permit an = in front of the first parameter. Comments are introduced by a hash (#).

To identify the menu items in the menu overview, set a title for every entry. The text (including any spaces) following the keyword title is displayed as a selectable option in the menu. All commands up to the next title are executed when this menu item is selected.

The simplest case is the redirection to boot loaders of other operating systems. The command is chainloader and the argument is usually the boot block of another partition, in GRUB block notation. For example:

chainloader (hd0,3)+1

The device names in GRUB are explained in Section “Naming Conventions for Hard Disks and Partitions”. This example specifies the first block of the fourth partition of the first hard disk.

Use the command kernel to specify a kernel image. The first argument is the path to the kernel image in a partition. The other arguments are passed to the kernel on its command line.

If the kernel does not have built-in drivers for access to the root partition or a recent Linux system with advanced hotplug features is used, initrd must be specified with a separate GRUB command whose only argument is the path to the initrd file. Because the loading address of the initrd is written into the loaded kernel image, the command initrd must follow after the kernel command.

The command root simplifies the specification of kernel and initrd files. The only argument of root is a device or a partition. This device is used for all kernel, initrd, or other file paths for which no device is explicitly specified until the next root command.

The boot command is implied at the end of every menu entry, so it does not need to be written into the menu file. However, if you use GRUB interactively for booting, you must enter the boot command at the end. The command itself has no arguments. It merely boots the loaded kernel image or the specified chain loader.

After writing all menu entries, define one of them as the default entry. Otherwise, the first one (entry 0) is used. You can also specify a time-out in seconds after which the default entry should boot. timeout and default usually precede the menu entries. An example file is described in Section “An Example Menu File”.

Naming Conventions for Hard Disks and Partitions

The naming convention GRUB uses for hard disks and partitions differ from that used for normal Linux devices. It more closely resembles the simple disk enumeration the BIOS does and the syntax is similar to that used in some BSD derivatives. In GRUB, the numbering of the partitions start with zero. This means that (hd0,0) is the first partition of the first hard disk. On a common desktop machine with a hard disk connected as primary master, the corresponding Linux device name is /dev/sda1.

The four possible primary partitions are assigned the partition numbers 0 to 3. The logical partitions are numbered from 4:

(hd0,0)   first primary partition of the first hard disk
(hd0,1)   second primary partition
(hd0,2)   third primary partition
(hd0,3)   fourth primary partition (usually an extended partition)
(hd0,4)   first logical partition
(hd0,5)   second logical partition

Being dependent on BIOS devices, GRUB does not distinguish between IDE, SATA, SCSI, and hardware RAID devices. All hard disks recognized by the BIOS or other controllers are numbered according to the boot sequence preset in the BIOS.

Unfortunately, it is often not possible to map the Linux device names to BIOS device names exactly. It generates this mapping with the help of an algorithm and saves it to the file device.map, which can be edited if necessary. Information about the file device.map is available in Section “The File device.map”.

A complete GRUB path consists of a device name written in parentheses and the path to the file in the file system in the specified partition. The path begins with a slash. For example, the bootable kernel could be specified as follows on a system with a single IDE hard disk containing Linux in its first partition:

(hd0,0)/boot/vmlinuz

An Example Menu File

The following example shows the structure of a GRUB menu file. The example installation has a Linux boot partition under /dev/sda5, a root partition under /dev/sda7 and a Windows installation under /dev/sda1.

gfxmenu (hd0,4)/boot/message
color white/blue black/light-gray
default 0
timeout 8

title linux
   root (hd0,4)
   kernel /boot/vmlinuz root=/dev/sda7 vga=791 resume=/dev/sda9
   initrd /boot/initrd

title windows
   rootnoverify (hd0,0)
   chainloader +1

title floppy
   rootnoverify (hd0,0)
   chainloader (fd0)+1

title failsafe
   root (hd0,4)
   kernel /boot/vmlinuz.shipped root=/dev/sda7 ide=nodma \
   apm=off acpi=off vga=normal nosmp maxcpus=0 3 noresume
   initrd /boot/initrd.shipped

The first block defines the configuration of the splash screen:

gfxmenu (hd0,4)/message

The background image message is located in the top directory of the /dev/sda5 partition.

color white/blue black/light-gray

Color scheme: white (foreground), blue (background), black (selection) and light gray (background of the selection). The color scheme has no effect on the splash screen, only on the customizable GRUB menu that you can access by exiting the splash screen with Esc.

default 0

The first menu entry title linux is the one to boot by default.

timeout 8

After eight seconds without any user input, GRUB automatically boots the default entry. To deactivate automatic boot, delete the timeout line. If you set timeout 0, GRUB boots the default entry immediately.

The second and largest block lists the various bootable operating systems. The sections for the individual operating systems are introduced by title.

The first entry (title linux) is responsible for booting openSUSE. The kernel (vmlinuz) is located in the first logical partition (the boot partition) of the first hard disk. Kernel parameters, such as the root partition and VGA mode, are appended here. The root partition is specified according to the Linux naming convention (/dev/sda7/) because this information is read by the kernel and has nothing to do with GRUB. The initrd is also located in the first logical partition of the first hard disk.

The second entry is responsible for loading Windows. Windows is booted from the first partition of the first hard disk (hd0,0). The command chainloader +1 causes GRUB to read and execute the first sector of the specified partition.

The next entry enables booting from floppy disk without modifying the BIOS settings.

The boot option failsafe starts Linux with a selection of kernel parameters that enables Linux to boot even on problematic systems.

The menu file can be changed whenever necessary. GRUB then uses the modified settings during the next boot. Edit the file permanently using YaST or an editor of your choice. Alternatively, make temporary changes interactively using the edit function of GRUB. See Section “Editing Menu Entries during the Boot Procedure”.

Editing Menu Entries during the Boot Procedure

In the graphical boot menu, select the operating system to boot with the arrow keys. If you select a Linux system, you can enter additional boot parameters at the boot prompt. To edit individual menu entries directly, press Esc to exit the splash screen and get to the GRUB text-based menu then press E. Changes made in this way only apply to the current boot and are not adopted permanently.

Keyboard Layout during the Boot Procedure

The US keyboard layout is the only one available when booting. See “US Keyboard Layout” (↑Start-Up).

Editing menu entries facilitates the repair of a defective system that can no longer be booted, because the faulty configuration file of the boot loader can be circumvented by manually entering parameters. Manually entering parameters during the boot procedure is also useful for testing new settings without impairing the native system.

After activating the editing mode, use the arrow keys to select the menu entry of the configuration to edit. To make the configuration editable, press E again. In this way, edit incorrect partitions or path specifications before they have a negative effect on the boot process. Press Enter to exit the editing mode and return to the menu. Then press B to boot this entry. Further possible actions are displayed in the help text at the bottom.

To enter changed boot options permanently and pass them to the kernel, open the file menu.lst as the user root and append the respective kernel parameters to the existing line, separated by spaces:

title linux
   root(hd0,0)
     kernel /vmlinuz root=/dev/sda3 additional parameter
   initrd /initrd

GRUB automatically adopts the new parameters the next time the system is booted. Alternatively, this change can also be made with the YaST boot loader module. Append the new parameters to the existing line, separated by spaces.

The File device.map

The file device.map maps GRUB and BIOS device names to Linux device names. In a mixed system containing IDE and SCSI hard disks, GRUB must try to determine the boot sequence by a special procedure, because GRUB may not have access to the BIOS information on the boot sequence. GRUB saves the result of this analysis in the file /boot/grub/device.map. For a system on which the boot sequence in the BIOS is set to IDE before SCSI, the file device.map could appear as follows:

(fd0)  /dev/fd0
(hd0)  /dev/sda
(hd1)  /dev/sdb

Because the order of IDE, SCSI and other hard disks depends on various factors and Linux is not able to identify the mapping, the sequence in the file device.map can be set manually. If you encounter problems when booting, check if the sequence in this file corresponds to the sequence in the BIOS and use the GRUB prompt to modify it temporarily, if necessary. After the Linux system has booted, the file device.map can be edited permanently with the YaST boot loader module or an editor of your choice.

After manually changing device.map, execute the following command to reinstall GRUB. This command causes the file device.map to be reloaded and the commands listed in grub.conf to be executed:

grub --batch < /etc/grub.conf

The File /etc/grub.conf

The third important GRUB configuration file after menu.lst and device.map is /etc/grub.conf. This file contains the commands, parameters and options the GRUB shell needs for installing the boot loader correctly:

setup --stage2=/boot/grub/stage2 --force-lba (hd0,1) (hd0,1)
   quit

This command tells GRUB to automatically install the boot loader to the second partition on the first hard disk (hd0,1) using the boot images located on the same partition. The --stage2=/boot/grub/stage2 parameter is needed to install the stage2 image from a mounted file system. Some BIOSes have a faulty LBA support implementation, --force-lba provides a solution to ignore them.

The File /etc/sysconfig/bootloader

This configuration file is only used when configuring the bootloader with YaST and every time a new kernel is installed. It is evaluated by the perl-bootloader library which modifies the bootloader configuration file (for example /boot/grub/menu.lst for GRUB) accordingly. /etc/sysconfig/bootloader is not a GRUB specific configuration file - the values are applied to any bootloader installed on openSUSE.

Bootloader Configuration after a Kernel Update

Every time a new kernel is installed, the perl bootloader writes a new bootloader configuration file (for example /boot/grub/menu.lst for GRUB) using the defaults specified in /etc/sysconfig/bootloadert. If you are using a customized set of kernel parameters, make sure to adjust the relevant defaults in /etc/sysconfig/bootloader according to your needs.

LOADER_TYPE

Specifies the bootloader installed on the system (e.g. GRUB or LILO). Please do not modify, use YaST to change the bootloader— see Procedure 17.6, “Changing the Boot Loader Type” for details.

DEFAULT_VGA / FAILSAFE_VGA / XEN_VGA

Screen resolution and color depth of the framebuffer used during booting are configured with the kernel parameter vga. These values define which resolution and color depth to use for the default boot entry, the failsafe and the XEN entry. The following values are valid:

Table 17.1. Screen Resolution and Color Depth Reference

640x480

800x600

1024x768

1280x1024

1600x1200

8bit

0x301

0x303

0x305

0x307

0x31C

15bit

0x310

0x313

0x316

0x319

0x31D

16bit

0x311

0x314

0x317

0x31A

0x31E

24bit

0x312

0x315

0x318

0x31B

0x31F

DEFAULT_APPEND / FAILSAFE_APPEND / XEN_KERNEL_APPEND

Kernel parameters (other than vga) that are automatically appended to the default, failsafe and XEN boot entries in the bootloader configuration file.

CYCLE_DETECTION / CYCLE_NEXT_ENTRY

Configure whether to use boot cycle detection and if so, which alternative entry from /boot/grub/menu.lst (e.g. Failsafe) to boot in case of a reboot cycle. See /usr/share/doc/packages/bootcycle/README for detailed information.

Setting a Boot Password

Even before the operating system is booted, GRUB enables access to file systems. Users without root permissions can access files in your Linux system to which they have no access once the system is booted. To block this kind of access or to prevent users from booting certain operating systems, set a boot password.

Boot Password and Splash Screen

If you use a boot password for GRUB, the usual splash screen is not displayed.

As the user root, proceed as follows to set a boot password:

At the root prompt, encrypt the password using grub-md5-crypt:

# grub-md5-crypt
Password: ****
Retype password: ****
Encrypted: $1$lS2dv/$JOYcdxIn7CJk9xShzzJVw/

Paste the encrypted string into the global section of the file menu.lst:

gfxmenu (hd0,4)/message
color white/blue black/light-gray
default 0
timeout 8
password --md5 $1$lS2dv/$JOYcdxIn7CJk9xShzzJVw/

Now GRUB commands can only be executed at the boot prompt after pressing P and entering the password. However, users can still boot all operating systems from the boot menu.

To prevent one or several operating systems from being booted from the boot menu, add the entry lock to every section in menu.lst that should not be bootable without entering a password. For example:

title linux
   kernel (hd0,4)/vmlinuz root=/dev/sda7 vga=791
   initrd (hd0,4)/initrd
   lock

After rebooting the system and selecting the Linux entry from the boot menu, the following error message is displayed:

Error 32: Must be authenticated

Press Enter to enter the menu. Then press P to get a password prompt. After entering the password and pressing Enter, the selected operating system (Linux in this case) should boot.

Configuring the Boot Loader with YaST

The easiest way to configure the boot loader in your openSUSE system is to use the YaST module. In the YaST Control Center, select System+Boot Loader. As in Figure 17.1, “Boot Loader Settings”, this shows the current boot loader configuration of your system and allows you to make changes.

Figure 17.1. Boot Loader Settings

Use the Section Management tab to edit, change and delete boot loader sections for the individual operating systems. To add an option, click Add. To change the value of an existing option, select it with the mouse and click Edit. To remove an existing entry, select it and click Delete. If you are not familiar with boot loader options, read Section “Booting with GRUB” first.

Use the Boot Loader Installation tab to view and change settings related to type, location and advanced loader settings.

Access advanced configuration options from the drop-down menu that opens after you click on Other. The build-in editor lets you change the GRUB configuration files (see Section “Booting with GRUB” for details). You can also delete the existing configuration and Start from Scratch or let YaST Propose a New Configuration. It is also possible to write the configuration to disk or reread the configuration from the disk. To restore the original Master Boot Record (MBR) that was saved during the installation, choose Restore MBR of Hard Disk.

Adjusting the Default Boot Entry

To change the system that is booted by default, proceed as follows:

Procedure 17.1. Setting the Default System

Open the Section Management tab.

Select the desired entry from the list.

Click Set as Default.

Click OK to activate these changes.

Modifying the Boot Loader Location

To modify the location of the boot loader, follow these steps:

Procedure 17.2. Changing the Boot Loader Location

Select the Boot Loader Installation tab and then choose one of the following options for Boot Loader Location:

Boot from Master Boot Record

This installs the boot loader in the MBR of the first disk (according to the boot sequence preset in the BIOS).

Boot from Root Partition

This installs the boot loader in the boot sector of the / partition (this is the default).

Boot from Boot Partition

This installs the boot loader in the boot sector of the /boot partition.

Boot from Extended Partition

This installs the boot loader in the extended partition container.

Custom Boot Partition

Use this option to specify the location of the boot loader manually.

Click OK to apply your changes.

Changing the Boot Loader Time-Out

The boot loader does not boot the default system immediately. During the time-out, you can select the system to boot or write some kernel parameters. To set the boot loader time-out, proceed as follows:

Procedure 17.3. Changing the Boot Loader Time-Out

Open the Boot Loader Installation tab.

Click Boot Loader Options.

Change the value of Time-Out in Seconds by typing in a new value and clicking the appropriate arrow key with your mouse, or by using the arrow keys on the keyboard.

Click OK twice to save the changes.

Setting a Boot Password

Using this YaST module, you can also set a password to protect booting. This gives you an additional level of security.

Procedure 17.4. Setting a Boot Loader Password

Open the Boot Loader Installation tab.

Click Boot Loader Options.

Activate the Protect Boot Loader with Password option with a click and type in your Password twice.

Click OK twice to save the changes.

Adjusting the Disk Order

If your computer has more than one hard disk, you can specify the boot sequence of the disks to match the BIOS setup of the machine (see Section “The File device.map”). To do so, proceed as follows:

Procedure 17.5. Setting the Disk Order

Open the Boot Loader Installation tab.

Click Boot Loader Installation Details.

If more than one disk is listed, select a disk and click Up or Down to reorder the displayed disks.

Click OK two times to save the changes.

Configuring Advanced Options

Advanced boot options can be configured via Boot Loader Installation+Boot Loader Options. Normally, it should not be necessary to change the default settings.

Set Active Flag in Partition Table for Boot Partition

Activates the partition that contains the boot loader. Some legacy operating systems (such as Windows 98) can only boot from an active partition.

Write Generic Boot Code to MBR

Replaces the current MBR with generic, operating system independent code.

Debugging Flag

Sets GRUB in debug mode where it displays messages to show disk activity.

Hide Boot Menu

Hides the boot menu and boots the default entry.

Use Trusted GRUB

Starts the Trusted GRUB which supports trusted computing functionality.

Enable Acoustic Signals

Enables or disables acoustic signals in GRUB.

Graphical Menu File

Path to the graphics file used when displaying the boot screen.

Serial Connection Parameters

If your machine is controlled via a serial console, activate this option and specify which COM port to use at which speed. See info grub or http://www.gnu.org/software/grub/manual/grub.html#Serial-terminal for details.

Changing Boot Loader Type

Set the boot loader type in Boot Loader Installation. The default boot loader in openSUSE is GRUB. To use LILO, proceed as follows:

LILO is unsupported

Using LILO is not recommended—it is unsupported on openSUSE. Only use it in special cases.

Procedure 17.6. Changing the Boot Loader Type

Select the Boot Loader Installation tab.

For Boot Loader, select LILO.

In the dialog box that opens, select one of the following actions:

Propose New Configuration

Have YaST propose a new configuration.

Convert Current Configuration

Have YaST convert the current configuration. When converting the configuration, some settings may be lost.

Start New Configuration from Scratch

Write a custom configuration. This action is not available during the installation of openSUSE.

Read Configuration Saved on Disk

Load your own /etc/lilo.conf. This action is not available during the installation of openSUSE.

Click OK two times to save the changes

During the conversion, the old GRUB configuration is saved to the disk. To use it, simply change the boot loader type back to GRUB and choose Restore Configuration Saved before Conversion. This action is available only on an installed system.

Custom Boot Loader

To use a boot loader other than GRUB or LILO, select Do Not Install Any Boot Loader. Read the documentation of your boot loader carefully before choosing this option.

Uninstalling the Linux Boot Loader

YaST can be used to uninstall the Linux boot loader and restore the MBR to the state it had prior to the installation of Linux. During the installation, YaST automatically creates a backup copy of the original MBR and restores it upon request.

To uninstall GRUB, start the YaST boot loader module (System+Boot Loader). Select Other+Restore MBR of Hard Disk and confirm with Yes, Rewrite.

Creating Boot CDs

If problems occur while booting your system using a boot manager or if the boot manager cannot be installed on your hard disk disk, it is also possible to create a bootable CD with all the necessary start-up files for Linux. This requires a CD writer be installed in your system.

Creating a bootable CD-ROM with GRUB merely requires a special form of stage2 called stage2_eltorito and, optionally, a customized menu.lst. The classic files stage1 and stage2 are not required.

Procedure 17.7. Creating Boot CDs

Change into a directory in which to create the ISO image, for example: cd /tmp

Create a subdirectory for GRUB and change into the newly created iso directory:

mkdir -p iso/boot/grub && cd iso

Copy the kernel, the files stage2_eltorito, initrd, menu.lst and message to iso/boot/:

cp /boot/vmlinuz boot/
cp /boot/initrd boot/
cp /boot/message boot/
cp /usr/lib/grub/stage2_eltorito boot/grub
cp /boot/grub/menu.lst boot/grub

Adjust the path entries in boot/grub/menu.lst to make them point to a CD-ROM device. Do this by replacing the device name of the hard disks, listed in the format (hdx,y), in the pathnames with (cd), the device name of the CD-ROM drive. You may also need to adjust the paths to the message file, the kernel and the initrd—they need to point to /boot/message, /boot/vmlinuz and /boot/initrd, respectively. After having made the adjustments, menu.lst should look similar to the following example:

timeout 8
default 0
gfxmenu (cd)/boot/message

title Linux
   root (cd)
   kernel /boot/vmlinuz root=/dev/sda5 vga=794 resume=/dev/sda1 \
   splash=verbose showopts
   initrd /boot/initrd

Use splash=silent instead of splash=verbose to prevent the boot messages from appearing during the boot procedure.

Create the ISO image with the following command:

genisoimage -R -b boot/grub/stage2_eltorito -no-emul-boot \
-boot-load-size 4 -boot-info-table -iso-level 2 -input-charset utf-8 \
-o grub.iso /tmp/iso

Write the resulting file grub.iso to a CD using your preferred utility. Do not burn the ISO image as a data file, but use the option for burning a CD image in your burning utility.

The Graphical SUSE Screen

The graphical SUSE screen is displayed on the first console if the option vga=value is used as a kernel parameter. If you install using YaST, this option is automatically activated in accordance with the selected resolution and the graphics card. There are three ways to disable the SUSE screen, if desired:

Disabling the SUSE Screen When Necessary

Enter the command echo 0 >/proc/splash on the command line to disable the graphical screen. To activate it again, enter echo 1 >/proc/splash.

Disabling the SUSE screen by default.

Add the kernel parameter splash=0 to your boot loader configuration. Chapter 17, The Boot Loader GRUB provides more information about this. However, if you prefer the text mode (the default in earlier versions) set vga=normal.

Completely Disabling the SUSE Screen

Compile a new kernel and disable the option Use splash screen instead of boot logo in framebuffer support.

Tip

Disabling framebuffer support in the kernel automatically disables the splash screen, as well. SUSE cannot provide any support for your system if you run it with a custom kernel.

Troubleshooting

This section lists some of the problems frequently encountered when booting with GRUB and a short description of possible solutions. Some of the problems are covered in articles in the Support Database at http://en.opensuse.org/SDB:SDB. Use the search dialog to search for keywords like GRUB, boot and boot loader.

GRUB and XFS

XFS leaves no room for stage1 in the partition boot block. Therefore, do not specify an XFS partition as the location of the boot loader. This problem can be solved by creating a separate boot partition that is not formatted with XFS.

GRUB Reports GRUB Geom Error

GRUB checks the geometry of connected hard disks when the system is booted. Sometimes, the BIOS returns inconsistent information and GRUB reports a GRUB Geom Error. In this case, update the BIOS.

GRUB also returns this error message if Linux was installed on an additional hard disk that is not registered in the BIOS. stage1 of the boot loader is found and loaded correctly, but stage2 is not found. This problem can be remedied by registering the new hard disk in the BIOS.

System Containing Several Hard Disks Does Not Boot

During the installation, YaST may have incorrectly determined the boot sequence of the hard disks. For example, GRUB may regard the IDE disk as hd0 and the SCSI disk as hd1, although the boot sequence in the BIOS is reversed (SCSI before IDE).

In this case, correct the hard disks during the boot process with the help of the GRUB command line. After the system has booted, edit device.map to apply the new mapping permanently. Then check the GRUB device names in the files /boot/grub/menu.lst and /boot/grub/device.map and reinstall the boot loader with the following command:

grub --batch < /etc/grub.conf

Booting Windows from the Second Hard Disk

Some operating systems, such as Windows, can only boot from the first hard disk. If such an operating system is installed on a hard disk other than the first hard disk, you can effect a logical change for the respective menu entry.

...
title windows
   map (hd0) (hd1)
   map (hd1) (hd0)
   chainloader(hd1,0)+1
...

In this example, Windows is started from the second hard disk. For this purpose, the logical order of the hard disks is changed with map. This change does not affect the logic within the GRUB menu file. Therefore, the second hard disk must be specified for chainloader.

For More Information

Extensive information about GRUB is available at http://www.gnu.org/software/grub/. Also refer to the grub info page. You can also search for the keyword “SDB:GRUB” in the Support Database at http://www.opensuse.org/ to get information about special issues.

Chapter 18. Special System Features

Abstract

This chapter starts with information about various software packages, the virtual consoles and the keyboard layout. We talk about software components like bash, cron and logrotate, because they were changed or enhanced during the last release cycles. Even if they are small or considered of minor importance, users may want to change their default behavior, because these components are often closely coupled with the system. The chapter concludes with a section about language and country-specific settings (I18N and L10N).

Information about Special Software Packages

The programs bash, cron, logrotate, locate, ulimit and free are very important for system administrators and many users. Man pages and info pages are two useful sources of information about commands, but both are not always available. GNU Emacs is a popular and very configurable text editor.

The bash Package and /etc/profile

Bash is the default system shell. When used as a login shell, it reads several initialization files. Bash processes them in the order they appear in this list:

/etc/profile

~/.profile

/etc/bash.bashrc

~/.bashrc

Make custom settings in ~/.profile or ~/.bashrc. To ensure the correct processing of these files, it is necessary to copy the basic settings from /etc/skel/.profile or /etc/skel/.bashrc into the home directory of the user. It is recommended to copy the settings from /etc/skel after an update. Execute the following shell commands to prevent the loss of personal adjustments:

mv ~/.bashrc ~/.bashrc.old
cp /etc/skel/.bashrc ~/.bashrc
mv ~/.profile ~/.profile.old
cp /etc/skel/.profile ~/.profile

Then copy personal adjustments back from the *.old files.

The cron Package

If you want to run commands regularly and automatically in the background at predefined times, cron is the tool to use. cron is driven by specially formatted time tables. Some of of them come with the system and users can write their own tables if needed.

The cron tables are located in /var/spool/cron/tabs. /etc/crontab serves as a systemwide cron table. Enter the username to run the command directly after the time table and before the command. In Example 18.1, “Entry in /etc/crontab”, root is entered. Package-specific tables, located in /etc/cron.d, have the same format. See the cron man page (man cron).

Example 18.1. Entry in /etc/crontab

1-59/5 * * * *   root   test -x /usr/sbin/atrun && /usr/sbin/atrun

You cannot edit /etc/crontab by calling the command crontab -e. This file must be loaded directly into an editor, then modified and saved.

A number of packages install shell scripts to the directories /etc/cron.hourly, /etc/cron.daily, /etc/cron.weekly and /etc/cron.monthly, whose execution is controlled by /usr/lib/cron/run-crons. /usr/lib/cron/run-crons is run every 15 minutes from the main table (/etc/crontab). This guarantees that processes that may have been neglected can be run at the proper time.

To run the hourly, daily or other periodic maintenance scripts at custom times, remove the time stamp files regularly using /etc/crontab entries (see Example 18.2, “/etc/crontab: Remove Time Stamp Files”, which removes the hourly one before every full hour, the daily one once a day at 2:14 a.m., etc.).

Example 18.2. /etc/crontab: Remove Time Stamp Files

59 *  * * *     root  rm -f /var/spool/cron/lastrun/cron.hourly
14 2  * * *     root  rm -f /var/spool/cron/lastrun/cron.daily
29 2  * * 6     root  rm -f /var/spool/cron/lastrun/cron.weekly
44 2  1 * *     root  rm -f /var/spool/cron/lastrun/cron.monthly

Or you can set DAILY_TIME in /etc/sysconfig/cron to the time at which cron.daily should start. The setting of MAX_NOT_RUN ensures that the daily tasks get triggered to run, even if the user did not turn on the computer at the specified DAILY_TIME for a longer period of time. The maximum value of MAX_NOT_RUN is 14 days.

The daily system maintenance jobs are distributed to various scripts for reasons of clarity. They are contained in the package aaa_base. /etc/cron.daily contains, for example, the components suse.de-backup-rpmdb, suse.de-clean-tmp or suse.de-cron-local.

Log Files: Package logrotate

There are a number of system services (daemons) that, along with the kernel itself, regularly record the system status and specific events onto log files. This way, the administrator can regularly check the status of the system at a certain point in time, recognize errors or faulty functions and troubleshoot them with pinpoint precision. These log files are normally stored in /var/log as specified by FHS and grow on a daily basis. The logrotate package helps control the growth of these files.

Configure logrotate with the file /etc/logrotate.conf. In particular, the include specification primarily configures the additional files to read. Programs that produce log files install individual configuration files in /etc/logrotate.d. For example, such files ship with the packages, e.g. apache2 (/etc/logrotate.d/apache2) and syslogd (/etc/logrotate.d/syslog).

Example 18.3. Example for /etc/logrotate.conf

# see "man logrotate" for details
# rotate log files weekly
weekly

# keep 4 weeks worth of backlogs
rotate 4

# create new (empty) log files after rotating old ones
create

# uncomment this if you want your log files compressed
#compress

# RPM packages drop log rotation information into this directory
include /etc/logrotate.d

# no packages own lastlog or wtmp - we'll rotate them here
#/var/log/wtmp {
#    monthly
#    create 0664 root utmp
#    rotate 1
#}

# system-specific logs may be also be configured here.

logrotate is controlled through cron and is called daily by /etc/cron.daily/logrotate.

Important

The create option reads all settings made by the administrator in /etc/permissions*. Ensure that no conflicts arise from any personal modifications.

The locate Command

locate, a command for quickly finding files, is not included in the standard scope of installed software. If desired, install the package findutils-locate. The updatedb process is started automatically every night or about 15 minutes after booting the system.

The ulimit Command

With the ulimit (user limits) command, it is possible to set limits for the use of system resources and to have these displayed. ulimit is especially useful for limiting available memory for applications. With this, an application can be prevented from co-opting too much of the system resources and slowing or even hanging up the operating system.

ulimit can be used with various options. To limit memory usage, use the options listed in Table 18.1, “ulimit: Setting Resources for the User”.

Table 18.1. ulimit: Setting Resources for the User

-m

The maximum resident set size

-v

The maximum amount of virtual memory available to the shell

-s

The maximum size of the stack

-c

The maximum size of core files created

-a

All current limits are reported

Systemwide entries can be made in /etc/profile. There, enable creation of core files (needed by programmers for debugging). A normal user cannot increase the values specified in /etc/profile by the system administrator, but can make special entries in ~/.bashrc.

Example 18.4. ulimit: Settings in ~/.bashrc

# Limits maximum resident set size (physical memory):
ulimit -m 98304

# Limits of virtual memory:
ulimit -v 98304

Memory allocations must be specified in KB. For more detailed information, see man bash.

Important

Not all shells support ulimit directives. PAM (for instance, pam_limits) offers comprehensive adjustment possibilities if you depend on encompassing settings for these restrictions.

The free Command

The free command is somewhat misleading if your goal is to find out how much RAM is currently being used. That information can be found in /proc/meminfo. These days, users with access to a modern operating systems, such as Linux, should not really need to worry much about memory. The concept of available RAM dates back to before the days of unified memory management. The slogan free memory is bad memory applies well to Linux. As a result, Linux has always made the effort to balance out caches without actually allowing free or unused memory.

Basically, the kernel does not have direct knowledge of any applications or user data. Instead, it manages applications and user data in a page cache. If memory runs short, parts of it are written to the swap partition or to files, from which they can initially be read with the help of the mmap command (see man mmap).

The kernel also contains other caches, such as the slab cache, where the caches used for network access are stored. This may explain the differences between the counters in /proc/meminfo. Most, but not all, of them can be accessed via /proc/slabinfo.

Man Pages and Info Pages

For some GNU applications (such as tar), the man pages are no longer maintained. For these commands, use the --help option to get a quick overview of the info pages, which provide more in-depth instructions. Info is GNU's hypertext system. Read an introduction to this system by entering info info. Info pages can be viewed with Emacs by entering emacs -f info or directly in a console with info. You can also use tkinfo, xinfo or the help system to view info pages.

Selecting Man Pages Using the man Command

With man man_page you normally display a man page for instant reading. Now, if a man page with the same name exists in different sections, man prompts the user, the page from which section shall be made visible. The user is then expected to type the section as the answer.

If you want to return to the previous behavior, set MAN_POSIXLY_CORRECT=1 in a shell initialization file such as ~/.bashrc.

Settings for GNU Emacs

GNU Emacs is a complex work environment. The following sections cover the configuration files processed when GNU Emacs is started. More information is available at http://www.gnu.org/software/emacs/.

On start-up, Emacs reads several files containing the settings of the user, system administrator and distributor for customization or preconfiguration. The initialization file ~/.emacs is installed to the home directories of the individual users from /etc/skel. .emacs, in turn, reads the file /etc/skel/.gnu-emacs. To customize the program, copy .gnu-emacs to the home directory (with cp /etc/skel/.gnu-emacs ~/.gnu-emacs) and make the desired settings there.

.gnu-emacs defines the file ~/.gnu-emacs-custom as custom-file. If users make settings with the customize options in Emacs, the settings are saved to ~/.gnu-emacs-custom.

With openSUSE, the emacs package installs the file site-start.el in the directory /usr/share/emacs/site-lisp. The file site-start.el is loaded before the initialization file ~/.emacs. Among other things, site-start.el ensures that special configuration files distributed with Emacs add-on packages, such as psgml, are loaded automatically. Configuration files of this type are located in /usr/share/emacs/site-lisp, too, and always begin with suse-start-. The local system administrator can specify systemwide settings in default.el.

More information about these files is available in the Emacs info file under Init File: info:/emacs/InitFile. Information about how to disable the loading of these files (if necessary) is also provided at this location.

The components of Emacs are divided into several packages:

The base package emacs.

emacs-x11 (usually installed): the program with X11 support.

emacs-nox: the program without X11 support.

emacs-info: online documentation in info format.

emacs-el: the uncompiled library files in Emacs Lisp. These are not required at runtime.

Numerous add-on packages can be installed if needed: emacs-auctex (LaTeX), psgml (SGML and XML), gnuserv (client and server operation) and others.

Virtual Consoles

Linux is a multiuser and multitasking system. The advantages of these features can be appreciated even on a stand-alone PC system. In text mode, there are six virtual consoles available. Switch between them using Alt+F1 through Alt+F6. The seventh console is reserved for X and the tenth console shows kernel messages. More or fewer consoles can be assigned by modifying the file /etc/inittab.

To switch to a console from X without shutting it down, use Ctrl+Alt+F1 to Ctrl+Alt+F6. To return to X, press Alt+F7.

Keyboard Mapping

To standardize the keyboard mapping of programs, changes were made to the following files:

/etc/inputrc
/etc/X11/Xmodmap
/etc/skel/.Xmodmap
/etc/skel/.exrc
/etc/skel/.less
/etc/skel/.lesskey
/etc/csh.cshrc
/etc/termcap
/usr/lib/terminfo/x/xterm
/usr/share/X11/app-defaults/XTerm
/usr/share/emacs/VERSION/site-lisp/term/*.el

These changes only affect applications that use terminfo entries or whose configuration files are changed directly (vi, less, etc.). Applications not shipped with the system should be adapted to these defaults.

Under X, the compose key (multikey) can be accessed using Ctrl+Shift (right). Also see the corresponding entry in /etc/X11/Xmodmap.

Further settings are possible using the X Keyboard Extension (XKB). This extension is also used by the desktop environments GNOME (gswitchit) and KDE (kxkb).

For More Information

Information about XKB is available in /etc/X11/xkb/README and the documents listed there.

Detailed information about the input of Chinese, Japanese and Korean (CJK) is available at Mike Fabian's page: http://www.suse.de/~mfabian/suse-cjk/input.html.

Language and Country-Specific Settings

The system is, to a very large extent, internationalized and can be flexibly modified for local needs. In other words, internationalization (I18N) allows specific localizations (L10N). The abbreviations I18N and L10N are derived from the first and last letters of the words and, in between, the number of letters omitted.

Settings are made with LC_ variables defined in the file /etc/sysconfig/language. This refers not only to native language support, but also to the categories Messages (Language), Character Set, Sort Order, Time and Date, Numbers and Money. Each of these categories can be defined directly with its own variable or indirectly with a master variable in the file language (see the locale man page).

RC_LC_MESSAGES, RC_LC_CTYPE, RC_LC_COLLATE, RC_LC_TIME, RC_LC_NUMERIC, RC_LC_MONETARY

These variables are passed to the shell without the RC_ prefix and represent the listed categories. The shell profiles concerned are listed below. The current setting can be shown with the command locale.

RC_LC_ALL

This variable, if set, overwrites the values of the variables already mentioned.

RC_LANG

If none of the previous variables are set, this is the fallback. By default, only RC_LANG is set. This makes it easier for users to enter their own values.

ROOT_USES_LANG

A yes or no variable. If set to no, root always works in the POSIX environment.

The variables can be set with the YaST sysconfig editor (see Section “Changing the System Configuration Using the YaST sysconfig Editor”). The value of such a variable contains the language code, country code, encoding and modifier. The individual components are connected by special characters:

  LANG=<language>[[_<COUNTRY>].<Encoding>[@<Modifier>]]

Some Examples

You should always set the language and country codes together. Language settings follow the standard ISO 639 available at http://www.evertype.com/standards/iso639/iso639-en.html and http://www.loc.gov/standards/iso639-2/. Country codes are listed in ISO 3166 available at http://www.din.de/gremien/nas/nabd/iso3166ma/codlstp1/en_listp1.html.

It only makes sense to set values for which usable description files can be found in /usr/lib/locale. Additional description files can be created from the files in /usr/share/i18n using the command localedef. The description files are part of the glibc-i18ndata package. A description file for en_US.UTF-8 (for English and United States) can be created with:

localedef -i en_US -f UTF-8 en_US.UTF-8

LANG=en_US.UTF-8

This is the default setting if American English is selected during installation. If you selected another language, that language is enabled but still with UTF-8 as the character encoding.

LANG=en_US.ISO-8859-1

This sets the language to English, country to United States and the character set to ISO-8859-1. This character set does not support the Euro sign, but it can be useful sometimes for programs that have not been updated to support UTF-8. The string defining the charset (ISO-8859-1 in this case) is then evaluated by programs like Emacs.

LANG=en_IE@euro

The above example explicitly includes the Euro sign in a language setting. This setting is basically obsolete now, as UTF-8 also covers the Euro symbol. It is only useful if an application supports ISO-8859-15 and not UTF-8.

SuSEconfig reads the variables in /etc/sysconfig/language and writes the necessary changes to /etc/SuSEconfig/profile and /etc/SuSEconfig/csh.cshrc. /etc/SuSEconfig/profile is read or sourced by /etc/profile. /etc/SuSEconfig/csh.cshrc is sourced by /etc/csh.cshrc. This makes the settings available systemwide.

Users can override the system defaults by editing their ~/.bashrc accordingly. For instance, if you do not want to use the systemwide en_US for program messages, include LC_MESSAGES=es_ES so that messages are displayed in Spanish instead.

Locale Settings in ~/.i18n

If you are not satisfied with locale system defaults, change the settings in ~/.i18n according to the Bash scripting syntax. Entries in ~/.i18n override system defaults from /etc/sysconfig/language. Use the same variable names but without the RC_ namespace prefixes. For example, use LANG instead of RC_LANG:

LANG=cs_CZ.UTF-8
LC_COLLATE=C

Settings for Language Support

Files in the category Messages are, as a rule, only stored in the corresponding language directory (like en) to have a fallback. If you set LANG to en_US and the message file in /usr/share/locale/en_US/LC_MESSAGES does not exist, it falls back to /usr/share/locale/en/LC_MESSAGES.

A fallback chain can also be defined, for example, for Breton to French or for Galician to Spanish to Portuguese:

LANGUAGE="br_FR:fr_FR"

LANGUAGE="gl_ES:es_ES:pt_PT"

If desired, use the Norwegian variants Nynorsk and Bokmål instead (with additional fallback to no):

LANG="nn_NO"

LANGUAGE="nn_NO:nb_NO:no"

or

LANG="nb_NO"

LANGUAGE="nb_NO:nn_NO:no"

Note that in Norwegian, LC_TIME is also treated differently.

One problem that can arise is a separator used to delimit groups of digits not being recognized properly. This occurs if LANG is set to only a two-letter language code like de, but the definition file glibc uses is located in /usr/share/lib/de_DE/LC_NUMERIC. Thus LC_NUMERIC must be set to de_DE to make the separator definition visible to the system.

For More Information

The GNU C Library Reference Manual, Chapter “Locales and Internationalization”. It is included in glibc-info.

Markus Kuhn, UTF-8 and Unicode FAQ for Unix/Linux, currently at http://www.cl.cam.ac.uk/~mgk25/unicode.html.

Unicode-Howto, by Bruno Haible: /usr/share/doc/howto/en/txt/Unicode-HOWTO.gz (package howto).

Chapter 19. Dynamic Kernel Device Management with udev

The kernel can add or remove almost any device in a running system. Changes in the device state (whether a device is plugged in or removed) need to be propagated to userspace. Devices need to be configured as soon as they are plugged in and recognized. Users of a certain device need to be informed about any changes in this device's recognized state. udev provides the needed infrastructure to dynamically maintain the device node files and symbolic links in the /dev directory. udev rules provide a way to plug external tools into the kernel device event processing. This enables you to customize udev device handling by, for example, adding certain scripts to execute as part of kernel device handling, or request and import additional data to evaluate during device handling.

The /dev Directory

The device nodes in the /dev directory provide access to the corresponding kernel devices. With udev, the /dev directory reflects the current state of the kernel. Every kernel device has one corresponding device file. If a device is disconnected from the system, the device node is removed.

The content of the /dev directory is kept on a temporary file system and all files are rendered at every system start-up. Manually created or modified files do not, by design, survive a reboot. Static files and directories that should always be present in the /dev directory regardless of the state of the corresponding kernel device can be placed in the /lib/udev/devices directory. At system start-up, the contents of that directory is copied to the /dev directory with the same ownership and permissions as the files in /lib/udev/devices.

Kernel uevents and udev

The required device information is exported by the sysfs file system. For every device the kernel has detected and initialized, a directory with the device name is created. It contains attribute files with device-specific properties.

Every time a device is added or removed, the kernel sends a uevent to notify udev of the change. The udev daemon reads and parses all provided rules from the /etc/udev/rules.d/*.rules files once at start-up and keeps them in memory. If rules files are changed, added or removed, the daemon can reload the in-memory representation of all rules with the command udevadm control reload_rules. This is also done when running /etc/init.d/boot.udev reload. For more details on udev rules and their syntax, refer to Section “Influencing Kernel Device Event Handling with udev Rules”.

Every received event is matched against the set of provides rules. The rules can add or change event environment keys, request a specific name for the device node to create, add symlinks pointing to the node or add programs to run after the device node is created. The driver core uevents are received from a kernel netlink socket.

Drivers, Kernel Modules and Devices

The kernel bus drivers probe for devices. For every detected device, the kernel creates an internal device structure while the driver core sends a uevent to the udev daemon. Bus devices identify themselves by a specially-formatted ID, which tells what kind of device it is. Usually these IDs consist of vendor and product ID and other subsystem-specific values. Every bus has its own scheme for these IDs, called MODALIAS. The kernel takes the device information, composes a MODALIAS ID string from it and sends that string along with the event. For a USB mouse, it looks like this:

MODALIAS=usb:v046DpC03Ed2000dc00dsc00dp00ic03isc01ip02

Every device driver carries a list of known aliases for devices it can handle. The list is contained in the kernel module file itself. The program depmod reads the ID lists and creates the file modules.alias in the kernel's /lib/modules directory for all currently available modules. With this infrastructure, module loading is as easy as calling modprobe for every event that carries a MODALIAS key. If modprobe $MODALIAS is called, it matches the device alias composed for the device with the aliases provided by the modules. If a matching entry is found, that module is loaded. All this is automatically triggered by udev.

Booting and Initial Device Setup

All device events happening during the boot process before the udev daemon is running are lost, because the infrastructure to handle these events resides on the root file system and is not available at that time. To cover that loss, the kernel provides a uevent file located in the device directory of every device in the sysfs file system. By writing add to that file, the kernel resends the same event as the one lost during boot. A simple loop over all uevent files in /sys triggers all events again to create the device nodes and perform device setup.

As an example, a USB mouse present during boot may not be initialized by the early boot logic, because the driver is not available at that time. The event for the device discovery was lost and failed to find a kernel module for the device. Instead of manually searching for possibly connected devices, udev just requests all device events from the kernel after the root file system is available, so the event for the USB mouse device just runs again. Now it finds the kernel module on the mounted root file system and the USB mouse can be initialized.

From userspace, there is no visible difference between a device coldplug sequence and a device discovery during runtime. In both cases, the same rules are used to match and the same configured programs are run.

Monitoring the Running udev Daemon

The program udevadm monitor can be used to visualize the driver core events and the timing of the udev event processes.

UEVENT[1185238505.276660] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1 (usb)
UDEV  [1185238505.279198] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1 (usb)
UEVENT[1185238505.279527] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0 (usb)
UDEV  [1185238505.285573] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0 (usb)
UEVENT[1185238505.298878] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10 (input)
UDEV  [1185238505.305026] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10 (input)
UEVENT[1185238505.305442] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10/mouse2 (input)
UEVENT[1185238505.306440] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10/event4 (input)
UDEV  [1185238505.325384] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10/event4 (input)
UDEV  [1185238505.342257] add   /devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10/mouse2 (input)

The UEVENT lines show the events the kernel has sent over netlink. The UDEV lines show the finished udev event handlers. The timing is printed in microseconds. The time between UEVENT and UDEV is the time udev took to process this event or the udev daemon has delayed its execution to synchronize this event with related and already running events. For example, events for hard disk partitions always wait for the main disk device event to finish, because the partition events may rely on the data that the main disk event has queried from the hardware.

udevadm monitor --env shows the complete event environment:

ACTION=add
DEVPATH=/devices/pci0000:00/0000:00:1d.2/usb3/3-1/3-1:1.0/input/input10
SUBSYSTEM=input
SEQNUM=1181
NAME="Logitech USB-PS/2 Optical Mouse"
PHYS="usb-0000:00:1d.2-1/input0"
UNIQ=""
EV=7
KEY=70000 0 0 0 0
REL=103
MODALIAS=input:b0003v046DpC03Ee0110-e0,1,2,k110,111,112,r0,1,8,amlsfw

udev also sends messages to syslog. The default syslog priority that controls which messages are sent to syslog is specified in the udev configuration file /etc/udev/udev.conf. The log priority of the running daemon can be changed with udevadm control log_priority=level/number.

Influencing Kernel Device Event Handling with udev Rules

A udev rule can match any property the kernel adds to the event itself or any information that the kernel exports to sysfs. The rule can also request additional information from external programs. Every event is matched against all provided rules. All rules are located in the /etc/udev/rules.d directory.

Every line in the rules file contains at least one key value pair. There are two kinds of keys, match and assignment keys. If all match keys match their values, the rule is applied and the assignment keys are assigned the specified value. A matching rule may specify the name of the device node, add symlinks pointing to the node or run a specified program as part of the event handling. If no matching rule is found, the default device node name is used to create the device node. Detailed information about the rule syntax and the provided keys to match or import data are described in the udev man page. The following example rules provide a basic introduction to udev rule syntax. The example rules are all taken from the udev default rule set that is located under /etc/udev/rules.d/50-udev-default.rules.

Example 19.1. Example udev Rules

# console
KERNEL=="console", MODE="0600", OPTIONS="last_rule"

# serial devices
KERNEL=="ttyUSB*", ATTRS{product}=="[Pp]alm*Handheld*", SYMLINK+="pilot"

# printer
SUBSYSTEM=="usb", KERNEL=="lp*", NAME="usb/%k", SYMLINK+="usb%k", GROUP="lp"

# kernel firmware loader
SUBSYSTEM=="firmware", ACTION=="add", RUN+="firmware.sh"

The console rule consists of three keys: one match key (KERNEL) and two assign keys (MODE, OPTIONS). The KERNEL match rule searches the device list for any items of the type console. Only exact matches are valid and trigger this rule to be executed. The MODE key assigns special permissions to the device node, in this case, read and write permissions to the owner of this device only. The OPTIONS key makes this rule the last rule to be applied to any device of this type. Any later rule matching this particular device type does not have any effect.

The serial devices rule is not available in 50-udev-default.rules anymore, but it is still worth considering. It consists of two match keys (KERNEL and ATTRS) and one assign key (SYMLINK). The KERNEL key searches for all devices of the ttyUSB type. Using the * wild card, this key matches several of these devices. The second match key, ATTRS, checks whether the product attribute file in sysfs for any ttyUSB device contains a certain string. The assign key (SYMLINK) triggers the addition of a symbolic link to this device under /dev/pilot. The operator used in this key (+=) tells udev to additionally perform this action, even if previous or later rules add other symbolic links. As this rule contains two match keys, it is only applied if both conditions are met.

The printer rule deals with USB printers and contains two match keys which must both apply to get the entire rule applied (SUBSYSTEM and KERNEL). Three assign keys deal with the naming for this device type (NAME), the creation of symbolic device links (SYMLINK) and the group membership for this device type (GROUP). Using the * wild card in the KERNEL key makes it match several lp printer devices. Substitutions are used in both, the NAME and the SYMLINK keys to extend these strings by the internal device name. For example, the symlink to the first lp USB printer would read /dev/usblp0.

The kernel firmware loader rule makes udev load additional firmware by an external helper script during runtime. The SUBSYSTEM match key searches for the firmware subsystem. The ACTION key checks whether any device belonging to the firmware subsystem has been added. The RUN+= key triggers the execution of the firmware.sh script to locate the firmware that is to be loaded.

Some general characteristics are common to all rules:

Each rule consists of one or more key value pairs separated by a comma.

A key's operation is determined by the operator. udev rules support several different operators.

Each given value must be enclosed by quotation marks.

Each line of the rules file represents one rule. If a rule is longer than just one line, use \ to join the different lines just as you would do in shell syntax.

udev rules support a shell-style pattern that matches the *, ?, and [] patterns.

udev rules support substitutions.

Using Operators in udev Rules

Creating keys you can choose from several different operators, depending on the type of key you want to create. Match keys will normally just be used to find a value that either matches or explicitly mismatches the search value. Match keys contain either of the following operators:

==

Compare for equality. If the key contains a search pattern, all results matching this pattern are valid.

!=

Compare for non-equality. If the key contains a search pattern, all results matching this pattern are valid.

Any of the following operators can be used with assign keys:

=

Assign a value to a key. If the key previously consisted of a list of values, the key resets and only the single value is assigned.

+=

Add a value to a key that contains a list of entries.

:=

Assign a final value. Disallow any later change by later rules.

Using Substitutions in udev Rules

udev rules support the use of placeholders and substitutions. Use them in a similar fashion as you would do in any other scripts. The following substitutions can be used with udev rules:

%r, $root

The device directory, /dev by default.

%p, $devpath

The value of DEVPATH.

%k, $kernel

The value of KERNEL or the internal device name.

%n, $number

The device number.

%N, $tempnode

The temporary name of the device file.

%M, $major

The major number of the device.

%m, $minor

The minor number of the device.

%s{attribute}, $attr{attribute}

The value of a sysfs attribute (specified by attribute).

%E{variable}, $attr{variable}

The value of an environment variable (specified by variable).

%c, $result

The output of PROGRAM.

%%

The % character.

$$

The $ character.

Using udev Match Keys

Match keys describe conditions that must be met before a udev rule can be applied. The following match keys are available:

ACTION

The name of the event action, for example, add or remove when adding or removing a device.

DEVPATH

The device path of the event device, for example, DEVPATH=/bus/pci/drivers/ipw3945 to search for all events related to the ipw3945 driver.

KERNEL

The internal (kernel) name of the event device.

SUBSYSTEM

The subsystem of the event device, for example, SUBSYSTEM=usb for all events related to USB devices.

ATTR{filename}

sysfs attributes of the event device. To match a string contained in the vendor attribute file name, you could use ATTR{vendor}=="On[sS]tream", for example.

KERNELS

Let udev search the device path upwards for a matching device name.

SUBSYSTEMS

Let udev search the device path upwards for a matching device subsystem name.

DRIVERS

Let udev search the device path upwards for a matching device driver name.

ATTRS{filename}

Let udev search the device path upwards for a device with matching sysfs attribute values.

ENV{key}

The value of an environment variable, for example, ENV{ID_BUS}="ieee1394 to search for all events related to the FireWire bus ID.

PROGRAM

Let udev execute an external program. To be successful, the program must return with exit code zero. The program's output, printed to stdout, is available to the RESULT key.

RESULT

Match the output string of the last PROGRAM call. Either include this key in the same rule as the PROGRAM key or in a later one.

Using udev Assign Keys

In contrast to the match keys described above, assign keys do not describe conditions that must be met. They assign values, names and actions to the device nodes maintained by udev.

NAME

The name of the device node to be created. Once a rule has set a node name, all other rules with a NAME key for this node are ignored.

SYMLINK

The name of a symlink related to the node to be created. Multiple matching rules can add symlinks to be created with the device node. You can also specify multiple symlinks for one node in one rule using the space character to separate the symlink names.

OWNER, GROUP, MODE

The permissions for the new device node. Values specified here overwrite anything that has been compiled in.

ATTR{key}

Specify a value to be written to a sysfs attribute of the event device. If the == operator is used, this key is also used to match against the value of a sysfs attribute.

ENV{key}

Tell udev to export a variable to the environment. If the == operator is used, this key is also used to match against an environment variable.

RUN

Tell udev to add a program to the list of programs to be executed for this device. Keep in mind to restrict this to very short tasks to avoid blocking further events for this device.

LABEL

Add a label where a GOTO can jump to.

GOTO

Tell udev to skip a number of rules and continue with the one that carries the label referenced by the GOTO key.

IMPORT{type}

Load variables into the event environment such as the output of an external program. udev imports variables of several different types. If no type is specified, udev tries to determine the type itself based on the executable bit of the file permissions.

program tells udev to execute an external program and import its output.

file tells udev to import a text file.

parent tells udev to import the stored keys from the parent device.

WAIT_FOR_SYSFS

Tells udev to wait for the specified sysfs file to be created for a certain device. For example, WAIT_FOR_SYSFS="ioerr_cnt" informs udev to wait until the ioerr_cnt file has been created.

OPTIONS

The OPTION key may have several possible values:

last_rule tells udev to ignore all later rules.

ignore_device tells udev to ignore this event completely.

ignore_remove tells udev to ignore all later remove events for the device.

all_partitions tells udev to create device nodes for all available partitions on a block device.

Persistent Device Naming

The dynamic device directory and the udev rules infrastructure make it possible to provide stable names for all disk devices—regardless of their order of recognition or the connection used for the device. Every appropriate block device the kernel creates is examined by tools with special knowledge about certain buses, drive types or file systems. Along with the dynamic kernel-provided device node name, udev maintains classes of persistent symbolic links pointing to the device:

/dev/disk
|-- by-id
|   |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B -> ../../sda
|   |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B-part1 -> ../../sda1
|   |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B-part6 -> ../../sda6
|   |-- scsi-SATA_HTS726060M9AT00_MRH453M4HWHG7B-part7 -> ../../sda7
|   |-- usb-Generic_STORAGE_DEVICE_02773 -> ../../sdd
|   `-- usb-Generic_STORAGE_DEVICE_02773-part1 -> ../../sdd1
|-- by-label
|   |-- Photos -> ../../sdd1
|   |-- SUSE10 -> ../../sda7
|   `-- devel -> ../../sda6
|-- by-path
|   |-- pci-0000:00:1f.2-scsi-0:0:0:0 -> ../../sda
|   |-- pci-0000:00:1f.2-scsi-0:0:0:0-part1 -> ../../sda1
|   |-- pci-0000:00:1f.2-scsi-0:0:0:0-part6 -> ../../sda6
|   |-- pci-0000:00:1f.2-scsi-0:0:0:0-part7 -> ../../sda7
|   |-- pci-0000:00:1f.2-scsi-1:0:0:0 -> ../../sr0
|   |-- usb-02773:0:0:2 -> ../../sdd
|   |-- usb-02773:0:0:2-part1 -> ../../sdd1
`-- by-uuid
    |-- 159a47a4-e6e6-40be-a757-a629991479ae -> ../../sda7
    |-- 3e999973-00c9-4917-9442-b7633bd95b9e -> ../../sda6
    `-- 4210-8F8C -> ../../sdd1

Files used by udev

/sys/*

Virtual file system provided by the Linux kernel, exporting all currently known devices. This information is used by udev to create device nodes in /dev

/dev/*

Dynamically created device nodes and static content copied at boot time from /lib/udev/devices/*

The following files and directories contain the crucial elements of the udev infrastructure:

/etc/udev/udev.conf

Main udev configuration file.

/etc/udev/rules.d/*

udev event matching rules.

/lib/udev/devices/*

Static /dev content.

/lib/udev/*

Helper programs called from udev rules.

For More Information

For more information about the udev infrastructure, refer to the following man pages:

udev

General information about udev, keys, rules and other important configuration issues.

udevadm

udevadm can be used to control the runtime behavior of udev, request kernel events, manage the event queue and provide simple debugging mechanisms.

udevd

Information about the udev event managing daemon.

Chapter 20. Bash and Bash Scripts

Abstract

These days many people use computers with a graphical user interface (GUI) like KDE or GNOME. Although they offer lots of features, their use is limited when it comes to the execution of automatical tasks. Shells are a good addition to GUIs and this chapter gives you an overview of some aspects of shells, in this case Bash.

What is “The Shell”?

Traditionally, the shell is Bash (Bourne again Shell). When this chapter speaks about “the shell” it means Bash. There are actually more available shells than Bash (ash, csh, ksh, zsh, …), each employing different features and characteristics. If you need further information about other shells, search for shell in YaST.

Knowing The Bash Configuration Files

A shell can be invoked as an:

interactive login shell. This is used when logging in to a machine, invoking Bash with the --login option or when logging in to a remote machine with SSH.

“ordinary” interactive shell. This is normally the case when starting xterm, konsole or similar tools.

non-interactive shell. This is used when invoking a shell script at the commandline.

Depending on which type of shell you use, different configuration files are being read. The following tables show the login and non-login shell configuration files.

Table 20.1. Bash Configuration Files for Login Shells

File

Description

/etc/profile

Do not modify this file, otherwise your modifications can be destroyed during your next update!

/etc/profile.local

Use this file if you extend /etc/profile

/etc/profile.d/

Contains system-wide configuration files for specific programs

~/.profile

Insert user specific configuration for login shells here

Table 20.2. Bash Configuration Files for Non-Login Shells

/etc/bash.bashrc

Do not modify this file, otherwise your modifications can be destroyed during your next update!

/etc/bash.bashrc.local

Use this file to insert your system-wide modifications for Bash only

~/bashrc

Insert user specific configuration here

Additionally, Bash uses some more files:

Table 20.3. Special Files for Bash

File

Description

~/.bash_history

Contains a list of all commands you have been typing

~/.bash_logout

Executed when logging out

The Directory Structure

The following table provides a short overview of the most important higher-level directories that you find on a Linux system. Find more detailed information about the directories and important subdirectories in the following list.

Table 20.4. Overview of a Standard Directory Tree

Directory

Contents

/

Root directory—the starting point of the directory tree.

/bin

Essential binary files, such as commands that are needed by both the system administrator and normal users. Usually also contains the shells, such as Bash.

/boot

Static files of the boot loader.

/dev

Files needed to access host-specific devices.

/etc

Host-specific system configuration files.

/home

Holds the home directories of all users who have accounts on the system. However, root's home directory is not located in /home but in /root.

/lib

Essential shared libraries and kernel modules.

/media

Mount points for removable media.

/mnt

Mount point for temporarily mounting a file system.

/opt

Add-on application software packages.

/root

Home directory for the superuser root.

/sbin

Essential system binaries.

/srv

Data for services provided by the system.

/tmp

Temporary files.

/usr

Secondary hierarchy with read-only data.

/var

Variable data such as log files.

/windows

Only available if you have both Microsoft Windows* and Linux installed on your system. Contains the Windows data.

The following list provides more detailed information and gives some examples of which files and subdirectories can be found in the directories:

/bin

Contains the basic shell commands that may be used both by root and by other users. These commands include ls, mkdir, cp, mv, rm and rmdir. /bin also contains Bash, the default shell in openSUSE.

/boot

Contains data required for booting, such as the boot loader, the kernel, and other data that is used before the kernel begins executing user-mode programs.

/dev

Holds device files that represent hardware components.

/etc

Contains local configuration files that control the operation of programs like the X Window System. The /etc/init.d subdirectory contains scripts that are executed during the boot process.

/home/username

Holds the private data of every user who has an account on the system. The files located here can only be modified by their owner or by the system administrator. By default, your e-mail directory and personal desktop configuration are located here in the form of hidden files and directories. KDE users find the personal configuration data for their desktop in .kde or .kde4 . GNOME users find it in .gconf. For information about hidden files, refer to “Key Features” (Chapter “Basic Concepts”, ↑Start-Up).

Home Directory in a Network Environment

If you are working in a network environment, your home directory may be mapped to a directory in the file system other than /home.

/lib

Contains the essential shared libraries needed to boot the system and to run the commands in the root file system. The Windows equivalent for shared libraries are DLL files.

/media

Contains mount points for removable media, such as CD-ROMs, USB sticks and digital cameras (if they use USB). /media generally holds any type of drive except the hard drive of your system. As soon as your removable medium has been inserted or connected to the system and has been mounted, you can access it from here.

/mnt

This directory provides a mount point for a temporarily mounted file system. root may mount file systems here.

/opt

Reserved for the installation of additional software. Optional software and larger add-on program packages can be found here. KDE3 is located here, whereas KDE4 and GNOME have moved to /usr now.

/root

Home directory for the root user. The personal data of root is located here.

/sbin

As the s indicates, this directory holds utilities for the superuser. /sbin contains the binaries essential for booting, restoring and recovering the system in addition to the binaries in /bin.

/srv

Holds data for services provided by the system, such as FTP and HTTP.

/tmp

This directory is used by programs that require the temporary storage of files.

/usr

/usr has nothing to do with users, but is the acronym for UNIX system resources. The data in /usr is static, read-only data that can be shared among various hosts compliant with the Filesystem Hierarchy Standard (FHS). This directory contains all application programs and establishes a secondary hierarchy in the file system. KDE4 and GNOME are also located here. /usr holds a number of subdirectories, such as /usr/bin, /usr/sbin, /usr/local, and /usr/share/doc.

/usr/bin

Contains generally accessible programs.

/usr/sbin

Contains programs reserved for the system administrator, such as repair functions.

/usr/local

In this directory the system administrator can install local, distribution-independent extensions.

/usr/share/doc

Holds various documentation files and the release notes for your system. In the manual subdirectory find an online version of this manual. If more than one language is installed, this directory may contain versions of the manuals for different languages.

Under packages find the documentation included in the software packages installed on your system. For every package, a subdirectory /usr/share/doc/packages/packagename is created that often holds README files for the package and sometimes examples, configuration files or additional scripts.

If HOWTOs are installed on your system /usr/share/doc also holds the howto subdirectory in which to find additional documentation on many tasks related to the setup and operation of Linux software.

/var

Whereas /usr holds static, read-only data, /var is for data which is written during system operation and thus is variable data, such as log files or spooling data. For an overview of the most important log files you can find under /var/log/, refer to “Log Files” (↑Start-Up).

/windows

Only available if you have both Microsoft Windows and Linux installed on your system. Contains the Windows data available on the Windows partition of your system. Whether you can edit the data in this directory depends on the file system your Windows partition uses. If it is FAT32, you can open and edit the files in this directory. For NTFS, openSUSE also includes write access support. However, the driver for the NTFS-3g file system has limited functionality. Learn more in Section “Accessing Files on Different OS on the Same Computer”.

Writing Shell Scripts

Shell scripts are a convenient way of doing all sorts of tasks: collecting data, searching for a word or phrase in a text and many other useful things. The following example shows a small shell script that prints a text:

Example 20.1. A Shell Script Printing a Text

#!/bin/sh
# Output the following line:
echo "Hello World"

The first line begins with the Shebang characters (#!) which is an indicator that this file is a script. The script is executed with the specified interpreter after the Shebang, in this case /bin/sh.

The second line is a comment beginning with the hash sign. It is recommended to comment difficult lines to remember what they do.

The third line uses the built-in command echo to print the corresponding text.

Before you can run this script you need some prerequisites:

Every script should contain a Shebang line (this is already the case with our example above.) If a script does not have this line, you have to call the interpreter manually.

You can save the script wherever you want. However, it is a good idea to save it in a directory where the shell can find it. The search path is determined by the environment variable PATH. Usually a normal user does not have write access to /usr/bin. Therefore it is recommended to save your scripts in the directory ~/bin/. The above example gets the name hello.sh.

The script needs executable permissions. Set the permissions with the following command:

chmod +x ~/bin/hello.sh

If you have fullfilled all of the above prerequisites, you can execute the script with either ~/bin/hello.sh or just hello.sh. The first call uses an absolute path whereas the second one searches for the command in each directory given by the PATH environment variable.

Redirecting Command Events

Each command can use three channels, either for input or output:

Standard Output.  This is the default output channel. Whenever a command prints something, it uses the standard output channel.

Standard Input.  If a command needs input from users or other commands, it uses this channel.

Standard Error.  Commands use this channel for error reporting.

To redirect these channels, there are the following possibilities:

Command > File

Saves the output of the command into a file, an existing file will be deleted. For example, the ls command writes its output into the file listing.txt:

ls > listing.txt

Command >> File

Appends the output of the command to a file. For example, the ls command appends its output to the file listing.txt:

ls >> listing.txt

Command < File

Reads the file as input for the given command. For example, the read command reads in the content of the file into the variable a:

read a < foo

Command1 | Command2

Redirects the output of the left command as input for the right command. For example, the cat command outputs the content of the /proc/cpuinfo file. This output is used by grep to filter only those lines which contain cpu:

cat /proc/cpuinfo | grep cpu

Every channel has a file descriptor: 0 (zero) for standard input, 1 for standard output and 2 for standard error. It is allowed to insert this file descriptor before a < or > character. For example, the following line searches for a file starting with foo, but suppresses its errors by redirecting it to /dev/null:

find / -name "foo*" 2>/dev/null

Using Aliases

An alias is a shortcut definition of one or more commands. The syntax for an alias is:

alias NAME=DEFINITION

For example, the following line defines an alias lt which outputs a long listing (option -l), sorts it by modification time (-t) and prints it in reverse order while sorting (-r):

alias lt='ls -ltr'

To view all alias definitions, use alias. Remove your alias with unalias.

Using Variables in Bash

A shell variable can be global or local. Global variables, or environment variables, can be accessed in all shells. In contrast, local variables are visible in the current shell only.

To view all environment variables, use the printenv command. If you need to know the value of a variable, insert the name of your variable as an argument:

printenv PATH

A variable, be it global or local, can be viewed with echo:

echo $PATH

To set a local variable, use a variable name followed by the equal sign, followed by the value:

PROJECT="SLED"

Do not insert spaces around the equal sign, otherwise you get an error. To set a environment variable, use export:

export NAME="tux"

To remove a variable, use unset:

unset NAME

The following table contains some common environment variables which can be used in you shell scripts:

Table 20.5. Useful Environment Variables

HOME

the home directory of the current user

HOST

the current host name

LANG

when a tool is localized, it uses the language from this environment variable. English can also be set to C

PATH

the search path of the shell, a list of directories separated by colon

PS1

specifies the normal prompt printed before each command

PS2

specifies the secondary prompt printed when you execute a multi-line command

PWD

current working directory

USER

the current user

Using Argument Variables

For example, if you have the script foo.sh you can execute it like this:

foo.sh "Tux Penguin" 2000

To access all the arguments which are passed to your script, you need positional parameters. These are $1 for the first argument, $2 for the second, and so on. You can have up to nine parameters. To get the script name, use $0.

The following script foo.sh prints all arguments from 1 to 4:

#!/bin/sh
echo \"$1\" \"$2\" \"$3\" \"$4\"

If you execute this script with the above arguments, you get:

"Tux Penguin" "2000" "" ""

Using Variable Substitution

Variable substitutions apply a pattern to the content of a variable either from the left or right side. The following list contains the possible syntax forms:

${VAR#pattern}

removes the shortest possible match from the left:

file=/home/tux/book/book.tar.bz2
echo ${file#*/}
home/tux/book/book.tar.bz2

${VAR##pattern}

removes the longest possible match from the left:

file=/home/tux/book/book.tar.bz2
echo ${file##*/}
book.tar.bz2

${VAR%pattern}

removes the shortest possible match from the right:

file=/home/tux/book/book.tar.bz2
echo ${file%.*}
/home/tux/book/book.tar

${VAR%%pattern}

removes the longest possible match from the right:

file=/home/tux/book/book.tar.bz2
echo ${file%%.*}
/home/tux/book/book

Grouping And Combining Commands

Shells allow you to concatenate and group commands for conditional execution. Each command returns an exit code which determines the success or failure of its operation. If it is 0 (zero) the command was successful, everything else marks an error which is specific to the command.

The following list shows, how commands can be grouped:

Command1 ; Command2

executes the commands in sequential order. The exit code is not checked. The following line displays the content of the file with cat and then prints its file properties with ls regardless of their exit codes:

cat filelist.txt ; ls -l filelist.txt

Command1 && Command2

runs the right command, if the left command was successful (logical AND). The following line displays the content of the file and prints its file properties only, when the previous command was successful (compare it with the previous entry in this list):

cat filelist.txt && ls -l filelist.txt

Command1 || Command2

runs the right command, when the left command has failed (logical OR). The following line creates only a directory in /home/wilber/bar when the creation of the directory in /home/tux/foo has failed:

mkdir /home/tux/foo || mkdir /home/wilber/bar

funcname(){ ... }

creates a shell function. You can use the positional parameters to access its arguments. The following line defines the function hello to print a short message:

hello() { echo "Hello $1"; }

You can call this function like this:

hello Tux

which prints:

Hello Tux

Working with Common Flow Constructs

To control the flow of your script, a shell has while, if, for and case constructs.

The if Control Command

The if command is used to check expressions. For example, the following code tests whether the current user is Tux:

if test $USER = "tux" then
  echo "Hello Tux."
else
  echo "You are not Tux."
fi

The test expression can be as complex or simple as possible. The following expression checks if the file foo.txt exists:

if test -e /tmp/foo.txt
then
  echo "Found foo.txt"
fi

Find more useful expressions at http://www.cyberciti.biz/nixcraft/linux/docs/uniqlinuxfeatures/lsst/ch03sec02.html.

Creating Loops With The For Command

The for loop allows you to execute commands to a list of entries. For example, the following code prints some information about PNG files in the current directory:

for i in *.png; do
 ls -l $i
done

For More Information

Important information about Bash is provided in the man pages man sh. More about this topic can be found in the following list:

http://tldp.org/LDP/Bash-Beginners-Guide/html/index.html—Bash Guide for Beginners

http://tldp.org/HOWTO/Bash-Prog-Intro-HOWTO.html—BASH Programming - Introduction HOW-TO

http://tldp.org/LDP/abs/html/index.html—Advanced Bash-Scripting Guide

http://www.grymoire.com/Unix/Sh.html—Sh - the Bourne Shell

Part V. Services

Chapter 21. Basic Networking

Abstract

Linux offers the necessary networking tools and features for integration into all types of network structures. Network access using a network card, modem or other device can be configured with YaST. Manual configuration is also possible. In this chapter only the fundamental mechanisms and the relevant network configuration files are covered.

Linux and other Unix operating systems use the TCP/IP protocol. It is not a single network protocol, but a family of network protocols that offer various services. The protocols listed in Table 21.1, “Several Protocols in the TCP/IP Protocol Family”, are provided for the purpose of exchanging data between two machines via TCP/IP. Networks combined by TCP/IP, comprising a worldwide network, are also referred to as “the Internet.”

RFC stands for Request for Comments. RFCs are documents that describe various Internet protocols and implementation procedures for the operating system and its applications. The RFC documents describe the setup of Internet protocols. To expand your knowledge of any of the protocols, refer to the appropriate RFC documents. These are available at http://www.ietf.org/rfc.html.

Table 21.1. Several Protocols in the TCP/IP Protocol Family

Protocol

Description

TCP

Transmission Control Protocol: a connection-oriented secure protocol. The data to transmit is first sent by the application as a stream of data and converted into the appropriate format by the operating system. The data arrives at the respective application on the destination host in the original data stream format it was initially sent. TCP determines whether any data has been lost or jumbled during the transmission. TCP is implemented wherever the data sequence matters.

UDP

User Datagram Protocol: a connectionless, insecure protocol. The data to transmit is sent in the form of packets generated by the application. The order in which the data arrives at the recipient is not guaranteed and data loss is possible. UDP is suitable for record-oriented applications. It features a smaller latency period than TCP.

ICMP

Internet Control Message Protocol: Essentially, this is not a protocol for the end user, but a special control protocol that issues error reports and can control the behavior of machines participating in TCP/IP data transfer. In addition, it provides a special echo mode that can be viewed using the program ping.

IGMP

Internet Group Management Protocol: This protocol controls machine behavior when implementing IP multicast.

As shown in Figure 21.1, “Simplified Layer Model for TCP/IP”, data exchange takes place in different layers. The actual network layer is the insecure data transfer via IP (Internet protocol). On top of IP, TCP (transmission control protocol) guarantees, to a certain extent, security of the data transfer. The IP layer is supported by the underlying hardware-dependent protocol, such as ethernet.

Figure 21.1. Simplified Layer Model for TCP/IP

The diagram provides one or two examples for each layer. The layers are ordered according to abstraction levels. The lowest layer is very close to the hardware. The uppermost layer, however, is almost a complete abstraction from the hardware. Every layer has its own special function. The special functions of each layer are mostly implicit in their description. The data link and physical layers represent the physical network used, such as ethernet.

Almost all hardware protocols work on a packet-oriented basis. The data to transmit is collected into packets (it cannot be sent all at once). The maximum size of a TCP/IP packet is approximately 64 KB. Packets are normally quite smaller, as the network hardware can be a limiting factor. The maximum size of a data packet on an ethernet is about fifteen hundred bytes. The size of a TCP/IP packet is limited to this amount when the data is sent over an ethernet. If more data is transferred, more data packets need to be sent by the operating system.

For the layers to serve their designated functions, additional information regarding each layer must be saved in the data packet. This takes place in the header of the packet. Every layer attaches a small block of data, called the protocol header, to the front of each emerging packet. A sample TCP/IP data packet traveling over an ethernet cable is illustrated in Figure 21.2, “TCP/IP Ethernet Packet”. The proof sum is located at the end of the packet, not at the beginning. This simplifies things for the network hardware.

Figure 21.2. TCP/IP Ethernet Packet

When an application sends data over the network, the data passes through each layer, all implemented in the Linux kernel except the physical layer. Each layer is responsible for preparing the data so it can be passed to the next layer. The lowest layer is ultimately responsible for sending the data. The entire procedure is reversed when data is received. Like the layers of an onion, in each layer the protocol headers are removed from the transported data. Finally, the transport layer is responsible for making the data available for use by the applications at the destination. In this manner, one layer only communicates with the layer directly above or below it. For applications, it is irrelevant whether data is transmitted via a 100 Mbit/s FDDI network or via a 56-Kbit/s modem line. Likewise, it is irrelevant for the data line which kind of data is transmitted, as long as packets are in the correct format.

IP Addresses and Routing

The discussion in this section is limited to IPv4 networks. For information about IPv6 protocol, the successor to IPv4, refer to Section “IPv6—The Next Generation Internet”.

IP Addresses

Every computer on the Internet has a unique 32-bit address. These 32 bits (or 4 bytes) are normally written as illustrated in the second row in Example 21.1, “Writing IP Addresses”.

Example 21.1. Writing IP Addresses

IP Address (binary):  11000000 10101000 00000000 00010100
IP Address (decimal):      192.     168.       0.      20

In decimal form, the four bytes are written in the decimal number system, separated by periods. The IP address is assigned to a host or a network interface. It can be used only once throughout the world. There are exceptions to this rule, but these are not relevant to the following passages.

The points in IP addresses indicate the hierarchical system. Until the 1990s, IP addresses were strictly categorized in classes. However, this system proved too inflexible and was discontinued. Now, classless routing (CIDR, classless interdomain routing) is used.

Netmasks and Routing

Netmasks are used to define the address range of a subnetwork. If two hosts are in the same subnetwork, they can reach each other directly. If they are not in the same subnetwork, they need the address of a gateway that handles all the traffic for the subnetwork. To check if two IP addresses are in the same subnet, simply “AND” both addresses with the netmask. If the result is identical, both IP addresses are in the same local network. If there are differences, the remote IP address, and thus the remote interface, can only be reached over a gateway.

To understand how the netmask works, look at Example 21.2, “Linking IP Addresses to the Netmask”. The netmask consists of 32 bits that identify how much of an IP address belongs to the network. All those bits that are 1 mark the corresponding bit in the IP address as belonging to the network. All bits that are 0 mark bits inside the subnetwork. This means that the more bits are 1, the smaller the subnetwork is. Because the netmask always consists of several successive 1 bits, it is also possible to just count the number of bits in the netmask. In Example 21.2, “Linking IP Addresses to the Netmask” the first net with 24 bits could also be written as 192.168.0.0/24.

Example 21.2. Linking IP Addresses to the Netmask

IP address (192.168.0.20):  11000000 10101000 00000000 00010100
Netmask   (255.255.255.0):  11111111 11111111 11111111 00000000
---------------------------------------------------------------
Result of the link:         11000000 10101000 00000000 00000000
In the decimal system:           192.     168.       0.       0

IP address (213.95.15.200): 11010101 10111111 00001111 11001000
Netmask    (255.255.255.0): 11111111 11111111 11111111 00000000
---------------------------------------------------------------
Result of the link:         11010101 10111111 00001111 00000000
In the decimal system:           213.      95.      15.       0

To give another example: all machines connected with the same ethernet cable are usually located in the same subnetwork and are directly accessible. Even when the subnet is physically divided by switches or bridges, these hosts can still be reached directly.

IP addresses outside the local subnet can only be reached if a gateway is configured for the target network. In the most common case, there is only one gateway that handles all traffic that is external. However, it is also possible to configure several gateways for different subnets.

If a gateway has been configured, all external IP packets are sent to the appropriate gateway. This gateway then attempts to forward the packets in the same manner—from host to host—until it reaches the destination host or the packet's TTL (time to live) expires.

Table 21.2. Specific Addresses

Address Type

Description

Base Network Address

This is the netmask AND any address in the network, as shown in Example 21.2, “Linking IP Addresses to the Netmask” under Result. This address cannot be assigned to any hosts.

Broadcast Address

This basically says, “Access all hosts in this subnetwork.” To generate this, the netmask is inverted in binary form and linked to the base network address with a logical OR. The above example therefore results in 192.168.0.255. This address cannot be assigned to any hosts.

Local Host

The address 127.0.0.1 is assigned to the “loopback device” on each host. A connection can be set up to your own machine with this address and with all addresses from the complete 127.0.0.0/8 loopback network as defined with IPv4. With IPv6 there is just one loopback address (::1).

Because IP addresses must be unique all over the world, you cannot just select random addresses. There are three address domains to use if you want to set up a private IP-based network. These cannot get any connection from the rest of the Internet, because they cannot be transmitted over the Internet. These address domains are specified in RFC 1597 and listed in Table 21.3, “Private IP Address Domains”.

Table 21.3. Private IP Address Domains

Network/Netmask

Domain

10.0.0.0/255.0.0.0

10.x.x.x

172.16.0.0/255.240.0.0

172.16.x.x – 172.31.x.x

192.168.0.0/255.255.0.0

192.168.x.x

IPv6—The Next Generation Internet

Due to the emergence of the WWW (World Wide Web), the Internet has experienced explosive growth, with an increasing number of computers communicating via TCP/IP in the past fifteen years. Since Tim Berners-Lee at CERN (http://public.web.cern.ch) invented the WWW in 1990, the number of Internet hosts has grown from a few thousand to about a hundred million.

As mentioned, an IPv4 address consists of only 32 bits. Also, quite a few IP addresses are lost—they cannot be used due to the way in which networks are organized. The number of addresses available in your subnet is two to the power of the number of bits, minus two. A subnetwork has, for example, 2, 6, or 14 addresses available. To connect 128 hosts to the Internet, for example, you need a subnetwork with 256 IP addresses, from which only 254 are usable, because two IP addresses are needed for the structure of the subnetwork itself: the broadcast and the base network address.

Under the current IPv4 protocol, DHCP or NAT (network address translation) are the typical mechanisms used to circumvent the potential address shortage. Combined with the convention to keep private and public address spaces separate, these methods can certainly mitigate the shortage. The problem with them lies in their configuration, which is a chore to set up and a burden to maintain. To set up a host in an IPv4 network, you need a number of address items, such as the host's own IP address, the subnetmask, the gateway address and maybe a name server address. All these items need to be known and cannot be derived from somewhere else.

With IPv6, both the address shortage and the complicated configuration should be a thing of the past. The following sections tell more about the improvements and benefits brought by IPv6 and about the transition from the old protocol to the new one.

Advantages

The most important and most visible improvement brought by the new protocol is the enormous expansion of the available address space. An IPv6 address is made up of 128 bit values instead of the traditional 32 bits. This provides for as many as several quadrillion IP addresses.

However, IPv6 addresses are not only different from their predecessors with regard to their length. They also have a different internal structure that may contain more specific information about the systems and the networks to which they belong. More details about this are found in Section “Address Types and Structure”.

The following is a list of some other advantages of the new protocol:

Autoconfiguration

IPv6 makes the network “plug and play” capable, which means that a newly set up system integrates into the (local) network without any manual configuration. The new host uses its automatic configuration mechanism to derive its own address from the information made available by the neighboring routers, relying on a protocol called the neighbor discovery (ND) protocol. This method does not require any intervention on the administrator's part and there is no need to maintain a central server for address allocation—an additional advantage over IPv4, where automatic address allocation requires a DHCP server.

Nevertheless if a router is connected to a switch, the router should send periodic advertisments with flags telling the hosts of a network how they should interact with each other. For more information, see RFC 2462 and the radvd.conf(5) manpage, and RFC 3315.

Mobility

IPv6 makes it possible to assign several addresses to one network interface at the same time. This allows users to access several networks easily, something that could be compared with the international roaming services offered by mobile phone companies: when you take your mobile phone abroad, the phone automatically logs in to a foreign service as soon as it enters the corresponding area, so you can be reached under the same number everywhere and are able to place an outgoing call just like in your home area.

Secure Communication

With IPv4, network security is an add-on function. IPv6 includes IPsec as one of its core features, allowing systems to communicate over a secure tunnel to avoid eavesdropping by outsiders on the Internet.

Backward Compatibility

Realistically, it would be impossible to switch the entire Internet from IPv4 to IPv6 at one time. Therefore, it is crucial that both protocols are able to coexist not only on the Internet, but also on one system. This is ensured by compatible addresses (IPv4 addresses can easily be translated into IPv6 addresses) and through the use of a number of tunnels. See Section “Coexistence of IPv4 and IPv6”. Also, systems can rely on a dual stack IP technique to support both protocols at the same time, meaning that they have two network stacks that are completely separate, such that there is no interference between the two protocol versions.

Custom Tailored Services through Multicasting

With IPv4, some services, such as SMB, need to broadcast their packets to all hosts in the local network. IPv6 allows a much more fine-grained approach by enabling servers to address hosts through multicasting—by addressing a number of hosts as parts of a group (which is different from addressing all hosts through broadcasting or each host individually through unicasting). Which hosts are addressed as a group may depend on the concrete application. There are some predefined groups to address all name servers (the all name servers multicast group), for example, or all routers (the all routers multicast group).

Address Types and Structure

As mentioned, the current IP protocol is lacking in two important aspects: there is an increasing shortage of IP addresses and configuring the network and maintaining the routing tables is becoming a more complex and burdensome task. IPv6 solves the first problem by expanding the address space to 128 bits. The second one is countered by introducing a hierarchical address structure, combined with sophisticated techniques to allocate network addresses, as well as multihoming (the ability to assign several addresses to one device, giving access to several networks).

When dealing with IPv6, it is useful to know about three different types of addresses:

Unicast

Addresses of this type are associated with exactly one network interface. Packets with such an address are delivered to only one destination. Accordingly, unicast addresses are used to transfer packets to individual hosts on the local network or the Internet.

Multicast

Addresses of this type relate to a group of network interfaces. Packets with such an address are delivered to all destinations that belong to the group. Multicast addresses are mainly used by certain network services to communicate with certain groups of hosts in a well-directed manner.

Anycast

Addresses of this type are related to a group of interfaces. Packets with such an address are delivered to the member of the group that is closest to the sender, according to the principles of the underlying routing protocol. Anycast addresses are used to make it easier for hosts to find out about servers offering certain services in the given network area. All servers of the same type have the same anycast address. Whenever a host requests a service, it receives a reply from the server with the closest location, as determined by the routing protocol. If this server should fail for some reason, the protocol automatically selects the second closest server, then the third one, and so forth.

An IPv6 address is made up of eight four-digit fields, each representing 16 bits, written in hexadecimal notation. They are separated by colons (:). Any leading zero bytes within a given field may be dropped, but zeros within the field or at its end may not. Another convention is that more than four consecutive zero bytes may be collapsed into a double colon. However, only one such :: is allowed per address. This kind of shorthand notation is shown in Example 21.3, “Sample IPv6 Address”, where all three lines represent the same address.

Example 21.3. Sample IPv6 Address

fe80 : 0000 : 0000 : 0000 : 0000 : 10 : 1000 : 1a4
fe80 :    0 :    0 :    0 :    0 : 10 : 1000 : 1a4
fe80 :                           : 10 : 1000 : 1a4

Each part of an IPv6 address has a defined function. The first bytes form the prefix and specify the type of address. The center part is the network portion of the address, but it may be unused. The end of the address forms the host part. With IPv6, the netmask is defined by indicating the length of the prefix after a slash at the end of the address. An address, as shown in Example 21.4, “IPv6 Address Specifying the Prefix Length”, contains the information that the first 64 bits form the network part of the address and the last 64 form its host part. In other words, the 64 means that the netmask is filled with 64 1-bit values from the left. Just like with IPv4, the IP address is combined with AND with the values from the netmask to determine whether the host is located in the same subnetwork or in another one.

Example 21.4. IPv6 Address Specifying the Prefix Length

fe80::10:1000:1a4/64

IPv6 knows about several predefined types of prefixes. Some of these are shown in Table 21.4, “Various IPv6 Prefixes”.

Table 21.4. Various IPv6 Prefixes

Prefix (hex)

Definition

00

IPv4 addresses and IPv4 over IPv6 compatibility addresses. These are used to maintain compatibility with IPv4. Their use still requires a router able to translate IPv6 packets into IPv4 packets. Several special addresses, such as the one for the loopback device, have this prefix as well.

2 or 3 as the first digit

Aggregatable global unicast addresses. As is the case with IPv4, an interface can be assigned to form part of a certain subnetwork. Currently, there are the following address spaces: 2001::/16 (production quality address space) and 2002::/16 (6to4 address space).

fe80::/10

Link-local addresses. Addresses with this prefix should not be routed and should therefore only be reachable from within the same subnetwork.

fec0::/10

Site-local addresses. These may be routed, but only within the network of the organization to which they belong. In effect, they are the IPv6 equivalent of the current private network address space, such as 10.x.x.x.

ff

These are multicast addresses.

A unicast address consists of three basic components:

Public Topology

The first part (which also contains one of the prefixes mentioned above) is used to route packets through the public Internet. It includes information about the company or institution that provides the Internet access.

Site Topology

The second part contains routing information about the subnetwork to which to deliver the packet.

Interface ID

The third part identifies the interface to which to deliver the packet. This also allows for the MAC to form part of the address. Given that the MAC is a globally unique, fixed identifier coded into the device by the hardware maker, the configuration procedure is substantially simplified. In fact, the first 64 address bits are consolidated to form the EUI-64 token, with the last 48 bits taken from the MAC, and the remaining 24 bits containing special information about the token type. This also makes it possible to assign an EUI-64 token to interfaces that do not have a MAC, such as those based on PPP or ISDN.

On top of this basic structure, IPv6 distinguishes between five different types of unicast addresses:

:: (unspecified)

This address is used by the host as its source address when the interface is initialized for the first time—when the address cannot yet be determined by other means.

::1 (loopback)

The address of the loopback device.

IPv4 Compatible Addresses

The IPv6 address is formed by the IPv4 address and a prefix consisting of 96 zero bits. This type of compatibility address is used for tunneling (see Section “Coexistence of IPv4 and IPv6”) to allow IPv4 and IPv6 hosts to communicate with others operating in a pure IPv4 environment.

IPv4 Addresses Mapped to IPv6

This type of address specifies a pure IPv4 address in IPv6 notation.

Local Addresses

There are two address types for local use:

link-local

This type of address can only be used in the local subnetwork. Packets with a source or target address of this type should not be routed to the Internet or other subnetworks. These addresses contain a special prefix (fe80::/10) and the interface ID of the network card, with the middle part consisting of zero bytes. Addresses of this type are used during automatic configuration to communicate with other hosts belonging to the same subnetwork.

site-local

Packets with this type of address may be routed to other subnetworks, but not to the wider Internet—they must remain inside the organization's own network. Such addresses are used for intranets and are an equivalent of the private address space defined by IPv4. They contain a special prefix (fec0::/10), the interface ID, and a 16 bit field specifying the subnetwork ID. Again, the rest is filled with zero bytes.

As a completely new feature introduced with IPv6, each network interface normally gets several IP addresses, with the advantage that several networks can be accessed through the same interface. One of these networks can be configured completely automatically using the MAC and a known prefix with the result that all hosts on the local network can be reached as soon as IPv6 is enabled (using the link-local address). With the MAC forming part of it, any IP address used in the world is unique. The only variable parts of the address are those specifying the site topology and the public topology, depending on the actual network in which the host is currently operating.

For a host to go back and forth between different networks, it needs at least two addresses. One of them, the home address, not only contains the interface ID but also an identifier of the home network to which it normally belongs (and the corresponding prefix). The home address is a static address and, as such, it does not normally change. Still, all packets destined to the mobile host can be delivered to it, regardless of whether it operates in the home network or somewhere outside. This is made possible by the completely new features introduced with IPv6, such as stateless autoconfiguration and neighbor discovery. In addition to its home address, a mobile host gets one or more additional addresses that belong to the foreign networks where it is roaming. These are called care-of addresses. The home network has a facility that forwards any packets destined to the host when it is roaming outside. In an IPv6 environment, this task is performed by the home agent, which takes all packets destined to the home address and relays them through a tunnel. On the other hand, those packets destined to the care-of address are directly transferred to the mobile host without any special detours.

Coexistence of IPv4 and IPv6

The migration of all hosts connected to the Internet from IPv4 to IPv6 is a gradual process. Both protocols will coexist for some time to come. The coexistence on one system is guaranteed where there is a dual stack implementation of both protocols. That still leaves the question of how an IPv6 enabled host should communicate with an IPv4 host and how IPv6 packets should be transported by the current networks, which are predominantly IPv4 based. The best solutions offer tunneling and compatibility addresses (see Section “Address Types and Structure”).

IPv6 hosts that are more or less isolated in the (worldwide) IPv4 network can communicate through tunnels: IPv6 packets are encapsulated as IPv4 packets to move them across an IPv4 network. Such a connection between two IPv4 hosts is called a tunnel. To achieve this, packets must include the IPv6 destination address (or the corresponding prefix) as well as the IPv4 address of the remote host at the receiving end of the tunnel. A basic tunnel can be configured manually according to an agreement between the hosts' administrators. This is also called static tunneling.

However, the configuration and maintenance of static tunnels is often too labor-intensive to use them for daily communication needs. Therefore, IPv6 provides for three different methods of dynamic tunneling:

6over4

IPv6 packets are automatically encapsulated as IPv4 packets and sent over an IPv4 network capable of multicasting. IPv6 is tricked into seeing the whole network (Internet) as a huge local area network (LAN). This makes it possible to determine the receiving end of the IPv4 tunnel automatically. However, this method does not scale very well and is also hampered by the fact that IP multicasting is far from widespread on the Internet. Therefore, it only provides a solution for smaller corporate or institutional networks where multicasting can be enabled. The specifications for this method are laid down in RFC 2529.

6to4

With this method, IPv4 addresses are automatically generated from IPv6 addresses, enabling isolated IPv6 hosts to communicate over an IPv4 network. However, a number of problems have been reported regarding the communication between those isolated IPv6 hosts and the Internet. The method is described in RFC 3056.

IPv6 Tunnel Broker

This method relies on special servers that provide dedicated tunnels for IPv6 hosts. It is described in RFC 3053.

Configuring IPv6

To configure IPv6, you normally do not need to make any changes on the individual workstations. IPv6 is enabled by default. You can disable it during installation in the network configuration step described in “Network Configuration” (Chapter “Installation with YaST”, ↑Start-Up). To disable or enable IPv6 on an installed system, use the YaST Network Settings module. On the Global Options tab, check or uncheck the Enable IPv6 option as necessary. To enable or disable IPv6 manually, edit /etc/modprobe.d/50-ipv6.conf and restart the system. If you want to enable it temporarily until the next reboot, enter modprobe -i ipv6 as root. It is basically impossible to unload the ipv6 module once loaded.

Because of the autoconfiguration concept of IPv6, the network card is assigned an address in the link-local network. Normally, no routing table management takes place on a workstation. The network routers can be queried by the workstation, using the router advertisement protocol, for what prefix and gateways should be implemented. The radvd program can be used to set up an IPv6 router. This program informs the workstations which prefix to use for the IPv6 addresses and which routers. Alternatively, use zebra/quagga for automatic configuration of both addresses and routing.

Consult the ifcfg-tunnel (5) man page to get information about how to set up various types of tunnels using the /etc/sysconfig/network files.

For More Information

The above overview does not cover the topic of IPv6 comprehensively. For a more in-depth look at the new protocol, refer to the following online documentation and books:

http://www.ipv6.org/

The starting point for everything about IPv6.

http://www.ipv6day.org

All information needed to start your own IPv6 network.

http://www.ipv6-to-standard.org/

The list of IPv6-enabled products.

http://www.bieringer.de/linux/IPv6/

Here, find the Linux IPv6-HOWTO and many links related to the topic.

RFC 2640

The fundamental RFC about IPv6.

IPv6 Essentials

A book describing all the important aspects of the topic is IPv6 Essentials by Silvia Hagen (ISBN 0-596-00125-8).

Name Resolution

DNS assists in assigning an IP address to one or more names and assigning a name to an IP address. In Linux, this conversion is usually carried out by a special type of software known as bind. The machine that takes care of this conversion is called a name server. The names make up a hierarchical system in which each name component is separated by a period. The name hierarchy is, however, independent of the IP address hierarchy described above.

Consider a complete name, such as jupiter.example.com, written in the format hostname.domain. A full name, referred to as a fully qualified domain name (FQDN), consists of a hostname and a domain name (example.com). The latter also includes the top level domain or TLD (com).

TLD assignment has become quite confusing for historical reasons. Traditionally, three-letter domain names are used in the USA. In the rest of the world, the two-letter ISO national codes are the standard. In addition to that, longer TLDs were introduced in 2000 that represent certain spheres of activity (for example, .info, .name, .museum).

In the early days of the Internet (before 1990), the file /etc/hosts was used to store the names of all the machines represented over the Internet. This quickly proved to be impractical in the face of the rapidly growing number of computers connected to the Internet. For this reason, a decentralized database was developed to store the hostnames in a widely distributed manner. This database, similar to the name server, does not have the data pertaining to all hosts in the Internet readily available, but can dispatch requests to other name servers.

The top of the hierarchy is occupied by root name servers. These root name servers manage the top level domains and are run by the Network Information Center (NIC). Each root name server knows about the name servers responsible for a given top level domain. Information about top level domain NICs is available at http://www.internic.net.

DNS can do more than just resolve hostnames. The name server also knows which host is receiving e-mails for an entire domain—the mail exchanger (MX).

For your machine to resolve an IP address, it must know about at least one name server and its IP address. Easily specify such a name server with the help of YaST. If you have a modem dial-up connection, you may not need to configure a name server manually at all. The dial-up protocol provides the name server address as the connection is made. The configuration of name server access with openSUSE® is described in Section “Configuring Hostname and DNS”. Setting up your own name server is described in Chapter 23, The Domain Name System.

The protocol whois is closely related to DNS. With this program, quickly find out who is responsible for any given domain.

MDNS and .local Domain Names

The .local top level domain is treated as link-local domain by the resolver. DNS requests are send as multicast DNS requests instead of normal DNS requests. If you already use the .local domain in your nameserver configuration, you must switch this option off in /etc/host.conf. For more information, see the host.conf manual page.

If you want to switch off MDNS during installation, use nomdns=1 as a boot parameter.

For more information on multicast DNS, see http://www.multicastdns.org.

Configuring a Network Connection with YaST

There are many supported networking types on Linux. Most of them use different device names and the configuration files are spread over several locations in the file system. For a detailed overview of the aspects of manual network configuration, see Section “Configuring a Network Connection Manually”.

During installation on a laptop (where NetworkManager is active by default) YaST configures all interfaces that have been detected. If NetworkManager is not active, only the first interface with link up (with a network cable connected) is automatically configured. Additional hardware can be configured any time on the installed system. The following sections describe the network configuration for all types of network connections supported by openSUSE.

Configuring the Network Card with YaST

To configure your wired or wireless network card in YaST, select Network Devices+Network Settings. After starting the module, YaST displays the Network Settings dialog with four tabs: Global Options, Overview, Hostname/DNS and Routing.

The Global Options tab allows you to set general networking options such as the use of NetworkManager, IPv6 and general DHCP options. For more information, see Section “Configuring Global Networking Options”.

The Overview tab contains information about installed network interfaces and configurations. Any properly detected network card is listed with its name. You can manually configure new cards, remove or change their configuration in this dialog. If you want to manually configure a card that was not automatically detected, see Section “Configuring an Undetected Network Card”. If you want to change the configuration of an already configured card, see Section “Changing the Configuration of a Network Card”.

The Hostname/DNS tab allows to set the hostname of the machine and name the servers to be used. For more information, see Section “Configuring Hostname and DNS”.

The Routing tab is used for the configuration of routing. See Section “Configuring Routing” for more information.

Figure 21.3. Configuring Network Settings

Configuring Global Networking Options

The Global Options tab of the YaST Network Settings module allows you to set important global networking options, such as the use of NetworkManager, IPv6 and DHCP client options. These settings are applicable for all network interfaces.

In the Network Setup Method choose the way network connections are managed. If you want a NetworkManager desktop applet to manage connections for all interfaces, choose User Controlled with NetworkManager. This option is well suited for switching between multiple wired and wireless networks. If you do not run a desktop environment (GNOME or KDE), or if your computer is a Xen server, virtual system, or provides network services such as DHCP or DNS in your network, use the Traditional Method with ifup. If NetworkManager is used, nm-applet should be used to configure network options and the Overview, Hostname/DNS and Routing tabs of the Network Settings module are disabled. For more information on NetworkManager, see “Using NetworkManager” (↑Start-Up).

In the IPv6 Protocol Settings choose whether you want to use the IPv6 protocol. It is possible to use IPv6 together with IPv4. By default, IPv6 is activated. However, in networks not using IPv6 protocol, response times can be faster with IPv6 protocol disabled. If you want to disable IPv6, uncheck the Enable IPv6 option. This disables autoload of the kernel module for IPv6. This will be applied after reboot.

In the DHCP Client Options configure options for the DHCP client. The DHCP Client Identifier must be different for each DHCP client on a single network. If left empty, it defaults to the hardware address of the network interface. However, if you are running several virtual machines using the same network interface and, therefore, the same hardware address, specify a unique free-form identifier here.

The Hostname to Send specifies a string used for the hostname option field when dhcpcd sends messages to DHCP server. Some DHCP servers update name server zones (forward and reverse records) according to this hostname (Dynamic DNS). Also, some DHCP servers require the Hostname to Send option field to contain a specific string in the DHCP messages from clients. Leave AUTO to send the current hostname (that is the one defined in /etc/HOSTNAME). Leave the option field empty for not sending any hostname. If yo do not want to change the default route according to the information from DHCP, uncheck Change Default Route via DHCP.

Changing the Configuration of a Network Card

To change the configuration of a network card, select a card from the list of the detected cards in Network Settings+Overview in YaST and click Edit. The Network Card Setup dialog appears in which to adjust the card configuration using the General, Address and Hardware tabs. For information about wireless card configuration, see Section “Configuration with YaST”.

Configuring IP Addresses

You can set the IP address of the network card or the way its IP address is determined in the Address tab of the Network Card Setup dialog. Both IPv4 and IPv6 addresses are supported. The network card can have No IP Address (which is useful for bonding devices), a Statically Assigned IP Address (IPv4 or IPv6) or a Dynamic Address assigned via DHCP or Zeroconf or both.

If using Dynamic Address, select whether to use DHCP Version 4 Only (for IPv4), DHCP Version 6 Only (for IPv6) or DHCP Both Version 4 and 6.

If possible, the first network card with link that is available during the installation is automatically configured to use automatic address setup via DHCP. In case of laptop computers where NetworkManager is active by default, all network cards are configured.

DHCP should also be used if you are using a DSL line but with no static IP assigned by the ISP (Internet Service Provider). If you decide to use DHCP, configure the details in DHCP Client Options in the Global Options tab of the Network Settings dialog of the YaST network card configuration module. If you have a virtual host setup where different hosts communicate through the same interface, an DHCP Client Identifier is necessary to distinguish them.

DHCP is a good choice for client configuration but it is not ideal for server configuration. To set a static IP address, proceed as follows:

Select a card from the list of detected cards in the Overview tab of the YaST network card configuration module and click Edit.

In the Address tab, choose Statically Assigned IP Address.

Enter the IP Address. Both IPv4 and IPv6 addresses can be used. Enter the network mask in Subnet Mask. If the IPv6 address is used, use Subnet Mask for prefix length in format /64.

Optionally, you can enter a fully qualified Hostname for this address, which will be written to the /etc/hosts configuration file.

Click Next.

To activate the configuration, click OK.

If you use the static address, the name servers and default gateway are not configured automatically. To configure name servers, proceed as described in Section “Configuring Hostname and DNS”. To configure a gateway, proceed as described in Section “Configuring Routing”.

Configuring Aliases

One network device can have multiple IP addresses, called aliases.

Aliases Are a Compatibility Feature

These so-called aliases resp. labels work with IPv4 only. With IPv6 they will be ignored. Using iproute2 network interfaces can have one or more addresses.

Using YaST to set an alias for your network card, proceed as follows:

Select a card from the list of detected cards in the Overview tab of the YaST network card configuration module and click Edit.

In the Address+Additional Addresses tab, click Add.

Enter Alias Name, IP Address, and Netmask. Do not include the interface name in the alias name.

Click OK.

Click Next.

To activate the configuration, click OK.

Changing the Device Name and Udev Rules

It is possible to change the device name of the network card when it is used. It is also possible to determine whether the network card should be identified by udev via its hardware (MAC) address or via the bus ID. The later option is preferable in large servers to ease hot swapping of cards. To set these options with YaST, proceed as follows:

Select a card from the list of detected cards in the Overview tab of the YaST Network Settings module and click Edit.

Go to the Hardware tab. The current device name is shown in Udev Rules. Click Change.

Select whether udev should identify the card by its MAC Address or Bus ID. The current MAC address and bus ID of the card are shown in the dialog.

To change the device name, check the Change Device Name option and edit the name.

Click OK and Next.

To activate the configuration, click OK.

Changing Network Card Kernel Driver

For some network cards, several kernel drivers may be available. If the card is already configured, YaST allows you to select a kernel driver to be used from a list of available suitable drivers. It is also possible to specify options for the kernel driver. To set these options with YaST, proceed as follows:

Select a card from the list of detected cards in the Overview tab of the YaST Network Settings module and click Edit.

Go to the Hardware tab.

Select the kernel driver to be used in Module Name. Enter any options for the selected driver in Options in the form option=value . If more options are used, they should be space-separated.

Click OK and Next.

To activate the configuration, click OK.

Activating the Network Device

If you use the traditional method with ifup, you can configure your device to either start during boot, on cable connection, on card detection, manually or never. To change device start-up, proceed as follows:

In YaST select a card from the list of detected cards in Network Devices+Network Settings and click Edit.

In the General tab, select the desired entry from Device Activation.

Choose At Boot Time to start the device during the system boot. With On Cable Connection, the interface is watched for any existing physical connection. With On Hotplug, the interface is set as soon as available. It is similar to the At Boot Time option, and only differs in the fact that no error occurs if the interface is not present at boot time. Choose Manually to control the interface manually with ifup. Choose Never to not start the device at all. The On NFSroot is similar to At Boot Time, but the interface does not shut down with the rcnetwork stop command. Use this if you use an nfs or iscsi root file system.

Click Next.

To activate the configuration, click OK.

Usually, only the system administrator can activate and deactivate network interfaces. If you want any user to be able to activate this interface via KInternet, select Enable Device Control for Non-root User via Kinternet.

Setting Up Maximum Transfer Unit Size

You can set a maximum transmission unit (MTU) for the interface. MTU refers to the largest allowed packet size in bytes. A higher MTU brings higher bandwidth efficiency. However, large packets can block up a slow interface for some time, increasing the lag for further packets.

In YaST select a card from the list of detected cards in Network Devices+Network Settings and click Edit.

In the General tab, select the desired entry from the Set MTU list.

Click Next.

To activate the configuration, click OK.

Configuring the Firewall

Without having to enter the detailed firewall setup as described in “Configuring the Firewall with YaST” (Chapter “Masquerading and Firewalls”, ↑Security Guide), you can determine the basic firewall setup for your device as part of the device setup. Proceed as follows:

Open the YaST Network Devices+Network Settings module. In the Overview tab, select a card from the list of detected cards and click Edit.

Enter the General tab of the Network Settings dialog.

Determine the firewall zone to which your interface should be assigned. The following options are available:

Firewall Disabled

This option is available only if the firewall is disabled and the firewall does not run at all. Only use this option if your machine is part of a greater network that is protected by an outer firewall.

Automatically Assign Zone

This option is available only if the firewall is enabled. The firewall is running and the interface is automatically assigned to a firewall zone. The zone which contains the keyword any or the external zone will be used for such an interface.

Internal Zone (Unprotected)

The firewall is running, but does not enforce any rules to protect this interface. Use this option if your machine is part of a greater network that is protected by an outer firewall. It is also useful for the interfaces connected to the internal network, when the machine has more network interfaces.

Demilitarized Zone

A demilitarized zone is an additional line of defense in front of an internal network and the (hostile) Internet. Hosts assigned to this zone can be reached from the internal network and from the Internet, but cannot access the internal network.

External Zone

The firewall is running on this interface and fully protects it against other—presumably hostile—network traffic. This is the default option.

Click Next.

Activate the configuration by clicking OK.

Configuring an Undetected Network Card

Your card may not be detected correctly. In this case, the card is not included in the list of detected cards. If you are sure that your system includes a driver for your card, you can configure it manually. You can also configure special network device types, such as bridge, bond, TUN or TAP. To configure an undetected network card (or a special device) proceed as follows:

In the Network Devices+Network Settings+Overview dialog in YaST click Add.

In the Hardware dialog, set the Device Type of the interface from the available options and Configuration Name. If the network card is a PCMCIA or USB device, activate the respective check box and exit this dialog with Next. Otherwise, you can define the kernel Module Name to be used for the card and its Options, if necessary.

Click Next.

Configure any needed options, such as the IP address, device activation or firewall zone for the interface in the General, Address, and Hardware tabs. For more information about the configuration options, see Section “Changing the Configuration of a Network Card”.

If you selected Wireless as the device type of the interface, configure the wireless connection in the next dialog.

Click Next.

To activate the new network configuration, click OK.

Configuring Hostname and DNS

If you did not change the network configuration during installation and the wired card was already available, a hostname was automatically generated for your computer and DHCP was activated. The same applies to the name service information your host needs to integrate into a network environment. If DHCP is used for network address setup, the list of domain name servers is automatically filled with the appropriate data. If a static setup is preferred, set these values manually.

To change the name of your computer and adjust the name server search list, proceed as follows:

Go to the Network Settings+Hostname/DNS tab in the Network Devices module in YaST.

Enter the Hostname and, if needed, the Domain Name. The domain is especially important if the machine is a mail server. Note that the hostname is global and applies to all set network interfaces.

If you are using DHCP to get an IP address, the hostname of your computer will be automatically set by the DHCP. You may want to disable this behavior if you connect to different networks, because they may assign different hostnames and changing the hostname at runtime may confuse the graphical desktop. To disable using DHCP to get an IP address uncheck Change Hostname via DHCP.

If you are using DHCP to get an IP address, your hostname will be written to /etc/hosts by default and be resolvable as a 127.0.0.2 IP address. To disable this uncheck Write Hostname to /etc/hosts but note that your hostname will not be resolvable without an active network.

In Modify DNS Configuration, select the way the DNS configuration (name servers, search list, the content of the /etc/resolv.conf file) is modified.

If the Use Default Policy option is selected, the configuration is handled by the netconfig script which merges the data defined statically (with YaST or in the configuration files) with data obtained dynamically (from the DHCP client or NetworkManager). This default policy is sufficient in most cases.

If the Only Manually option is selected, netconfig is not allowed to modify the /etc/resolv.conf file. However, this file can be edited manually.

If the Custom Policy option is selected, a Custom Policy Rule string defining the merge policy should be specified. The string consists of a comma-separated list of interface names to be considered a valid source of settings. Except for complete interface names, basic wildcards to match multiple interfaces are allowed, as well. For example, eth* ppp? will first target all eth and then all ppp0-ppp9 interfaces. There are two special policy values that indicate how to apply the static settings defined in the /etc/sysconfig/network/config file:

STATIC

The static settings have to be merged together with the dynamic settings.

STATIC_FALLBACK

The static settings are used only when no dynamic configuration is avalaible.

For more information, see the man 8 netconfig.

Enter the Name Servers and fill in the Domain Search list. Name servers must be specified by IP addresses, such as 192.168.1.116, not by hostnames. Names specified in the Domain Search tab are domain names used for resolving hostnames without a specified domain. If more than one Domain Search is used, separate domains with commas or white space.

To activate the configuration, click OK.

Configuring Routing

To make your machine communicate with other machines and other networks, routing information must be given to make network traffic take the correct path. If DHCP is used, this information is automatically provided. If a static setup is used, this data must be added manually.

In YaST go to Network Settings+Routing.

Enter the IP address of the Default Gateway (IPv4 and IPv6 if necessary). The default gateway matches every possible destination, but if any other entry exists that matches the required address, use this instead of the default route.

More entries can be entered in the Routing Table. Enter the Destination network IP address, Gateway IP address and the Netmask. Select the Device through which the traffic to the defined network will be routed (the minus sign stands for any device). To omit any of these values, use the minus sign -. To enter a default gateway into the table, use default in the Destination field.

Note

If more default routes are used, it is possible to specify the metric option to determine which route has a higher priority. To specify the metric option, enter - metric number in Options. The route with the highest metric is used as default. If the network device is disconnected, its route will be removed and the next one will be used. However, the current kernel does not use metric in static routing, only routing daemons like multipathd do.

If the system is a router, enable the IP Forwarding option in the Network Settings.

To activate the configuration, click OK.

Modem

In the YaST Control Center, access the modem configuration under Network Devices+Modem. If your modem was not automatically detected, go to the Modem Devices tab and open the dialog for manual configuration by clicking Add. Enter the interface to which the modem is connected under Modem Device.

CDMA and GPRS Modems

Configure supported CDMA and GPRS modems with the YaST Modem module just as you would configure regular modems.

Figure 21.4. Modem Configuration

If you are behind a private branch exchange (PBX), you may need to enter a dial prefix. This is often a zero. Consult the instructions that came with the PBX to find out. Also select whether to use tone or pulse dialing, whether the speaker should be on and whether the modem should wait until it detects a dial tone. The last option should not be enabled if the modem is connected to an exchange.

Under Details, set the baud rate and the modem initialization strings. Only change these settings if your modem was not detected automatically or if it requires special settings for data transmission to work. This is mainly the case with ISDN terminal adapters. Leave this dialog by clicking OK. To delegate control over the modem to the normal user without root permissions, activate Enable Device Control for Non-root User via Kinternet. In this way, a user without administrator permissions can activate or deactivate an interface. Under Dial Prefix Regular Expression, specify a regular expression. The Dial Prefix in KInternet, which can be modified by the normal user, must match this regular expression. If this field is left empty, the user cannot set a different Dial Prefix without administrator permissions.

In the next dialog, select the ISP. To choose from a predefined list of ISPs operating in your country, select Country. Alternatively, click New to open a dialog in which to provide the data for your ISP. This includes a name for the dial-up connection and ISP as well as the login and password provided by your ISP. Enable Always Ask for Password to be prompted for the password each time you connect.

In the last dialog, specify additional connection options:

Dial on Demand

If you enable Dial on Demand, set at least one name server. Use this feature only if your Internet connection is inexpensive, because there are programs that periodically request data from the Internet.

Modify DNS when Connected

This option is enabled by default, with the effect that the name server address is updated each time you connect to the Internet.

Automatically Retrieve DNS

If the provider does not transmit its domain name server after connecting, disable this option and enter the DNS data manually.

Automatically Reconnect

If this options is enabled, the connection is automatically reestablished after failure.

Ignore Prompts

This option disables the detection of any prompts from the dial-up server. If the connection build-up is slow or does not work at all, try this option.

External Firewall Interface

Selecting this option activates the firewall and sets the interface as external. This way, you are protected from outside attacks for the duration of your Internet connection.

Idle Time-Out (seconds)

With this option, specify a period of network inactivity after which the modem disconnects automatically.

IP Details

This opens the address configuration dialog. If your ISP does not assign a dynamic IP address to your host, disable Dynamic IP Address then enter your host's local IP address and the remote IP address. Ask your ISP for this information. Leave Default Route enabled and close the dialog by selecting OK.

Selecting Next returns to the original dialog, which displays a summary of the modem configuration. Close this dialog with OK.

ISDN

Use this module to configure one or several ISDN cards for your system. If YaST did not detect your ISDN card, click on Add in the ISDN Devices tab and manually select your card. Multiple interfaces are possible, but several ISPs can be configured for one interface. In the subsequent dialogs, set the ISDN options necessary for the proper functioning of the card.

Figure 21.5. ISDN Configuration

In the next dialog, shown in Figure 21.5, “ISDN Configuration”, select the protocol to use. The default is Euro-ISDN (EDSS1), but for older or larger exchanges, select 1TR6. If you are in the US, select NI1. Select your country in the relevant field. The corresponding country code then appears in the field next to it. Finally, provide your Area Code and the Dial Prefix if necessary. If you do not want to log all your ISDN traffic, uncheck the Start ISDN Log option.

Activate Device defines how the ISDN interface should be started: At Boot Time causes the ISDN driver to be initialized each time the system boots. Manually requires you to load the ISDN driver as root with the command rcisdn start. On Hotplug, used for PCMCIA or USB devices, loads the driver after the device is plugged in. When finished with these settings, select OK.

In the next dialog, specify the interface type for your ISDN card and add ISPs to an existing interface. Interfaces may be either the SyncPPP or the RawIP type, but most ISPs operate in the SyncPPP mode, which is described below.

Figure 21.6. ISDN Interface Configuration

The number to enter for My Phone Number depends on your particular setup:

ISDN Card Directly Connected to Phone Outlet

A standard ISDN line provides three phone numbers (called multiple subscriber numbers, or MSNs). If the subscriber asked for more, there may be up to 10. One of these MSNs must be entered here, but without your area code. If you enter the wrong number, your phone operator automatically falls back to the first MSN assigned to your ISDN line.

ISDN Card Connected to a Private Branch Exchange

Again, the configuration may vary depending on the equipment installed:

Smaller private branch exchanges (PBX) built for home purposes mostly use the Euro-ISDN (EDSS1) protocol for internal calls. These exchanges have an internal S0 bus and use internal numbers for the equipment connected to them.

Use one of the internal numbers as your MSN. You should be able to use at least one of the exchange's MSNs that have been enabled for direct outward dialing. If this does not work, try a single zero. For further information, consult the documentation delivered with your phone exchange.

Larger phone exchanges designed for businesses normally use the 1TR6 protocol for internal calls. Their MSN is called EAZ and usually corresponds to the direct-dial number. For the configuration under Linux, it should be sufficient to enter the last digit of the EAZ. As a last resort, try each of the digits from 1 to 9.

For the connection to be terminated just before the next charge unit is due, enable ChargeHUP. However, remember that may not work with every ISP. You can also enable channel bundling (multilink PPP) by selecting the corresponding option. Finally, you can enable the firewall for your link by selecting External Firewall Interface and Restart Firewall. To enable the normal user without administrator permissions to activate or deactivate the interface, select the Enable Device Control for Non-root User via KInternet.

Details opens a dialog in which to implement more complex connection schemes which are not relevant for normal home users. Leave the Details dialog by selecting OK.

In the next dialog, configure IP address settings. If you have not been given a static IP by your provider, select Dynamic IP Address. Otherwise, use the fields provided to enter your host's local IP address and the remote IP address according to the specifications of your ISP. If the interface should be the default route to the Internet, select Default Route. Each host can only have one interface configured as the default route. Leave this dialog by selecting Next.

The following dialog allows you to set your country and select an ISP. The ISPs included in the list are call-by-call providers only. If your ISP is not in the list, select New. This opens the Provider Parameters dialog in which to enter all the details for your ISP. When entering the phone number, do not include any blanks or commas among the digits. Finally, enter your login and the password as provided by the ISP. When finished, select Next.

To use Dial on Demand on a stand-alone workstation, specify the name server (DNS server) as well. Most ISPs support dynamic DNS, which means the IP address of a name server is sent by the ISP each time you connect. For a single workstation, however, you still need to provide a placeholder address like 192.168.22.99. If your ISP does not support dynamic DNS, specify the name server IP addresses of the ISP. If desired, specify a time-out for the connection—the period of network inactivity (in seconds) after which the connection should be automatically terminated. Confirm your settings with Next. YaST displays a summary of the configured interfaces. To activate these settings, select OK.

Cable Modem

In some countries it is quite common to access the Internet through the TV cable network. The TV cable subscriber usually gets a modem that is connected to the TV cable outlet on one side and to a computer network card on the other (using a 10Base-TG twisted pair cable). The cable modem then provides a dedicated Internet connection with a fixed IP address.

Depending on the instructions provided by your ISP, when configuring the network card either select Dynamic Address or Statically Assigned IP Address. Most providers today use DHCP. A static IP address often comes as part of a special business account.

For further information about the configuration of cable modems, read the Support Database article on the topic, which is available online at http://en.opensuse.org/SDB:Setting_Up_an_Internet_Connection_via_Cable_Modem_with_SuSE_Linux_8.0_or_Higher.

DSL

To configure your DSL device, select the DSL module from the YaST Network Devices section. This YaST module consists of several dialogs in which to set the parameters of DSL links based on one of the following protocols:

PPP over Ethernet (PPPoE)

PPP over ATM (PPPoATM)

CAPI for ADSL (Fritz Cards)

Point-to-Point Tunneling Protocol (PPTP)—Austria

In the DSL Devices tab of the DSL Configuration Overview dialog, you will find a list of installed DSL devices. To change the configuration of a DSL device, select it in the list and click Edit. If you click Add, you can manually configure a new DSL device.

The configuration of a DSL connection based on PPPoE or PPTP requires that the corresponding network card be set up in the correct way. If you have not done so yet, first configure the card by selecting Configure Network Cards (see Section “Configuring the Network Card with YaST”). In the case of a DSL link, addresses may be assigned automatically but not via DHCP, which is why you should not enable the option Dynamic Address. Instead, enter a static dummy address for the interface, such as 192.168.22.1. In Subnet Mask, enter 255.255.255.0. If you are configuring a stand-alone workstation, leave Default Gateway empty.

Tip

Values in IP Address and Subnet Mask are only placeholders. They are only needed to initialize the network card and do not represent the DSL link as such.

In the first DSL configuration dialog (see Figure 21.7, “DSL Configuration”), select the PPP Mode and the Ethernet Card to which the DSL modem is connected (in most cases, this is eth0). Then use Activate Device to specify whether the DSL link should be established during the boot process. Click Enable Device Control for Non-root User via KInternet to authorize the normal user without root permissions to activate or deactivate the interface with KInternet.

In the next dialog select your country and choose from a number of ISPs operating in it. The details of any subsequent dialogs of the DSL configuration depend on the options set so far, which is why they are only briefly mentioned in the following paragraphs. For details on the available options, read the detailed help available from the dialogs.

Figure 21.7. DSL Configuration

To use Dial on Demand on a stand-alone workstation, also specify the name server (DNS server). Most ISPs support dynamic DNS—the IP address of a name server is sent by the ISP each time you connect. For a single workstation, however, provide a placeholder address like 192.168.22.99. If your ISP does not support dynamic DNS, enter the name server IP address provided by your ISP.

Idle Time-Out (seconds) defines a period of network inactivity after which to terminate the connection automatically. A reasonable time-out value is between 60 and 300 seconds. If Dial on Demand is disabled, it may be useful to set the time-out to zero to prevent automatic hang-up.

The configuration of T-DSL is very similar to the DSL setup. Just select T-Online as your provider and YaST opens the T-DSL configuration dialog. In this dialog, provide some additional information required for T-DSL—the line ID, the T-Online number, the user code and your password. All of these should be included in the information you received after subscribing to T-DSL.

NetworkManager

NetworkManager is the ideal solution for laptops and other portable computers. With NetworkManager, you do not need to worry about configuring network interfaces and switching between networks when you are moving.

NetworkManager and ifup

However, NetworkManager is not a suitable solution for all cases, so you can still choose between the traditional method for managing network connections (ifup) and NetworkManager. If you want to manage your network connection with NetworkManager, enable NetworkManager in the YaST Network Settings module as described in “Enabling NetworkManager” (Chapter “Using NetworkManager”, ↑Start-Up) and configure your network connections with NetworkManager. For a list of use cases and a detailed description how to configure and use NetworkManager, refer to “Using NetworkManager” (↑Start-Up).

Some differences between ifup and NetworkManager include:

root Privileges

If you use NetworkManager for network setup, you can easily switch, stop or start your network connection at any time from within your desktop environment using an applet. NetworkManager also makes it possible to change and configure wireless card connections without requiring root privileges. For this reason, NetworkManager is the ideal solution for a mobile workstation.

Traditional configuration with ifup also provides some ways to switch, stop or start the connection with or without user intervention, like user-managed devices. However, this always requires root privileges to change or configure a network device. This is often a problem for mobile computing, where it is not possible to preconfigure all the connection possibilities.

Types of Network Connections

Both traditional configuration and NetworkManager can handle network connections with a wireless network (with WEP, WPA-PSK, and WPA-Enterprise access), dial-up and wired networks using DHCP and static configuration. They also support connection through VPN.

NetworkManager tries to keep your computer connected at all times using the best connection available. If the network cable is accidentally disconnected, it tries to reconnect. It can find the network with the best signal strength from the list of your wireless connections and automatically use it to connect. To get the same functionality with ifup, a great deal of configuration effort is required.

NetworkManager Functionality and Configuration Files

The individual network connection settings created with NetworkManager are stored in configuration profiles. The system connections configured with either NetworkManager or YaST can be found in /etc/sysconfig/network/ifcfg-*. Any user-defined connections are stored in GConf for GNOME or $HOME/.kde4/share/apps/networkmanagement/* for KDE.

In case no profile is configured, NetworkManager automatically creates one and names it Auto $INTERFACE-NAME. That is made in an attempt to work without any configuration for as many cases as (securely) possible. If the automatically created profiles do not suit your needs, use the network connection configuration dialogs provided by KDE or GNOME to modify them as desired. For more information, refer to “Configuring Network Connections” (Chapter “Using NetworkManager”, ↑Start-Up).

Controlling and Locking Down NetworkManager Features

On centrally administered machines, certain NetworkManager features can be controlled or disabled with PolicyKit, for example if a user is allowed to modify administrator defined connections or if a user is allowed to define his own network configurations. To view or change the respective NetworkManager policies, start the graphical Authorizations tool for PolicyKit. In the tree on the left side, find them below the network-manager-settings entry. For an introduction to PolicyKit and details on how to use it, refer to “PolicyKit” (↑Security Guide).

Configuring a Network Connection Manually

Manual configuration of the network software should always be the last alternative. Using YaST is recommended. However, this background information about the network configuration can also assist your work with YaST.

When the kernel detects a network card and creates a corresponding network interface, it assigns the device a name depending on the order of device discovery, or order of the loading of the kernel modules. The default kernel device names are only predictable in very simple or tightly controlled hardware environments. Systems which allow adding or removing hardware during runtime or support automatic configuration of devices cannot expect stable network device names assigned by the kernel across reboots.

However, all system configuration tools rely on persistent interface names. The problem is solved by udev. The udev persistent net generator (/lib/udev/rules.d/75-persistent-net-generator.rules) generates a rule matching the hardware (using its hardware address by default) and assigns a persistently unique interface for the hardware. The udev database of network interfaces is stored in the file /etc/udev/rules.d/70-persistent-net.rules. Every line in the file describes one network interface and specifies its persistent name. System administrators can change the assigned names by editing the NAME="" entries. The persistent rules can also be modified using YaST.

Table 21.5, “Manual Network Configuration Scripts” summarizes the most important scripts involved in the network configuration.

Table 21.5. Manual Network Configuration Scripts

Command

Function

ifup, ifdown, ifstatus

The if scripts start or stop network interfaces, or return the status of the specified interface. For more information, see the ifup manual page.

rcnetwork

The rcnetwork script can be used to start, stop or restart all network interfaces (or just a specified one). Use rcnetwork stop to stop, rcnetwork start to start and rcnetwork restart to restart network interfaces. If you want to stop, start or restart just one interface, use the command followed by the interface name, for example rcnetwork restart eth0. The rcnetwork status command displays the state of the interfaces, their IP addresses and whether a DHCP client is running. With rcnetwork stop-all-dhcp-clients and rcnetwork restart-all-dhcp-clients you can stop or restart DHCP clients running on network interfaces.

For more information about udev and persistent device names, see Chapter 19, Dynamic Kernel Device Management with udev.

Configuration Files

This section provides an overview of the network configuration files and explains their purpose and the format used.

/etc/sysconfig/network/ifcfg-*

These files contain the configurations for network interfaces. They include information such as the start mode and the IP address. Possible parameters are described in the manual page of ifup. Additionally, most variables from the files dhcp, wireless and config can be used in the ifcfg-* files if a general setting should be used for only one interface.

For ifcfg.template, see Section “/etc/sysconfig/network/config, /etc/sysconfig/network/dhcp, and /etc/sysconfig/network/wireless”.

/etc/sysconfig/network/config, /etc/sysconfig/network/dhcp, and /etc/sysconfig/network/wireless

The file config contains general settings for the behavior of ifup, ifdown and ifstatus. dhcp contains settings for DHCP and wireless for wireless LAN cards. The variables in all three configuration files are commented. Some of the variables from /etc/sysconfig/network/config can also be used in ifcfg-* files, where they are given a higher priority. The /etc/sysconfig/network/ifcfg.template file lists variables that can be specified in a per interface scope. However, most of the /etc/sysconfig/network/config variables are global and cannot be overriden in ifcfg-files. For example NETWORKMANAGER or NETCONFIG_* variables are global.

/etc/sysconfig/network/routes and /etc/sysconfig/network/ifroute-*

The static routing of TCP/IP packets is determined here. All the static routes required by the various system tasks can be entered in the /etc/sysconfig/network/routes file: routes to a host, routes to a host via a gateway and routes to a network. For each interface that needs individual routing, define an additional configuration file: /etc/sysconfig/network/ifroute-*. Replace * with the name of the interface. The entries in the routing configuration files look like this:

# Destination     Dummy/Gateway     Netmask            Device
#
127.0.0.0         0.0.0.0           255.255.255.0      lo
204.127.235.0     0.0.0.0           255.255.255.0      eth0
default           204.127.235.41    0.0.0.0            eth0
207.68.156.51     207.68.145.45     255.255.255.255    eth1
192.168.0.0       207.68.156.51     255.255.0.0        eth1

The route's destination is in the first column. This column may contain the IP address of a network or host or, in the case of reachable name servers, the fully qualified network or hostname.

The second column contains the default gateway or a gateway through which a host or network can be accessed. The third column contains the netmask for networks or hosts behind a gateway. For example, the mask is 255.255.255.255 for a host behind a gateway.

The fourth column is only relevant for networks connected to the local host such as loopback, Ethernet, ISDN, PPP and dummy device. The device name must be entered here.

An (optional) fifth column can be used to specify the type of a route. Columns that are not needed should contain a minus sign - to ensure that the parser correctly interprets the command. For details, refer to the routes(5) man page.

/etc/resolv.conf

The domain to which the host belongs is specified in this file (keyword search). Also listed is the status of the name server address to access (keyword nameserver). Multiple domain names can be specified in the file. When resolving a name that is not fully qualified, an attempt is made to generate one by attaching the individual search entries. Multiple name servers can be specified in multiple lines, each beginning with nameserver. Comments are preceded by # signs. Example 21.5, “/etc/resolv.conf” shows what /etc/resolv.conf could look like.

However, the /etc/resolv.conf should not be edited by hand. Instead, it is generated by the netconfig script. To define static DNS configuration without using YaST, edit the appropriate variables manually in the /etc/sysconfig/network/config file: NETCONFIG_DNS_STATIC_SEARCHLIST (list of DNS domain names used for hostname lookup), NETCONFIG_DNS_STATIC_SERVERS (list of name server IP addresses to use for hostname lookup), NETCONFIG_DNS_FORWARDER (defines the name of the DNS forwarder that has to be configured). To disable DNS configuration using netconfig, set NETCONFIG_DNS_POLICY=''. For more information about netconfig, see man 8 netconfig.

Example 21.5. /etc/resolv.conf

# Our domain
search example.com
#
# We use dns.example.com (192.168.1.116) as nameserver
nameserver 192.168.1.116

/sbin/netconfig

netconfig is a modular tool to manage additional network configuration settings. It merges statically defined settings with settings provided by autoconfiguration mechanisms as dhcp or ppp according to a predefined policy. The required changes are applied to the system by calling the netconfig modules that are responsible for modifying a configuration file and restarting a service or a similar action.

netconfig recognizes three main actions. The netconfig modify and netconfig remove commands are used by daemons such as dhcp or ppp to provide or remove settings to netconfig. Only the netconfig update command is available for the user:

modify

The netconfig modify command modifies the current interface and service specific dynamic settings and updates the network configuration. Netconfig reads settings from standard input or from a file specified with the --lease-file filename option and internally stores them until a system reboot (or the next modify or remove action). Already existing settings for the same interface and service combination are overwritten. The interface is specified by the -i interface_name parameter. The service is specified by the -s service_name parameter.

remove

The netconfig remove command removes the dynamic settings provided by a modificatory action for the specified interface and service combination and updates the network configuration. The interface is specified by the -i interface_name parameter. The service is specified by the -s service_name parameter.

update

The netconfig update command updates the network configuration using current settings. This is useful when the policy or the static configuration has changed.

The netconfig policy and the static configuration settings are defined either manually or using YaST in the /etc/sysconfig/network/config file. The dynamic configuration settings provided by autoconfiguration tools as dhcp or ppp are delivered directly by these tools with the netconfig modify and netconfig remove actions. NetworkManager also uses netconfig modify and netconfig remove actions. When NetworkManager is enabled, netconfig (in policy mode auto) uses only NetworkManager settings, ignoring settings from any other interfaces configured using the traditional ifup method. If NetworkManager does not provide any setting, static settings are used as a fallback. A mixed usage of NetworkManager and the traditional ifup method is not supported.

For more information about netconfig, see man 8 netconfig.

/etc/hosts

In this file, shown in Example 21.6, “/etc/hosts”, IP addresses are assigned to hostnames. If no name server is implemented, all hosts to which an IP connection will be set up must be listed here. For each host, enter a line consisting of the IP address, the fully qualified hostname, and the hostname into the file. The IP address must be at the beginning of the line and the entries separated by blanks and tabs. Comments are always preceded by the # sign.

Example 21.6. /etc/hosts

127.0.0.1 localhost
192.168.2.100 jupiter.example.com jupiter
192.168.2.101 venus.example.com venus

/etc/networks

Here, network names are converted to network addresses. The format is similar to that of the hosts file, except the network names precede the addresses. See Example 21.7, “/etc/networks”.

Example 21.7. /etc/networks

loopback     127.0.0.0
localnet     192.168.0.0

/etc/host.conf

Name resolution—the translation of host and network names via the resolver library—is controlled by this file. This file is only used for programs linked to libc4 or libc5. For current glibc programs, refer to the settings in /etc/nsswitch.conf. A parameter must always stand alone in its own line. Comments are preceded by a # sign. Table 21.6, “Parameters for /etc/host.conf” shows the parameters available. A sample /etc/host.conf is shown in Example 21.8, “/etc/host.conf”.

Table 21.6. Parameters for /etc/host.conf

order hosts, bind

Specifies in which order the services are accessed for the name resolution. Available arguments are (separated by blank spaces or commas):

hosts: searches the /etc/hosts file

bind: accesses a name server

nis: uses NIS

multi on/off

Defines if a host entered in /etc/hosts can have multiple IP addresses.

nospoof on spoofalert on/off

These parameters influence the name server spoofing but do not exert any influence on the network configuration.

trim domainname

The specified domain name is separated from the hostname after hostname resolution (as long as the hostname includes the domain name). This option is useful only if names from the local domain are in the /etc/hosts file, but should still be recognized with the attached domain names.

Example 21.8. /etc/host.conf

# We have named running
order hosts bind
# Allow multiple address
multi on

/etc/nsswitch.conf

The introduction of the GNU C Library 2.0 was accompanied by the introduction of the Name Service Switch (NSS). Refer to the nsswitch.conf(5) man page and The GNU C Library Reference Manual for details.

The order for queries is defined in the file /etc/nsswitch.conf. A sample nsswitch.conf is shown in Example 21.9, “/etc/nsswitch.conf”. Comments are preceded by # signs. In this example, the entry under the hosts database means that a request is sent to /etc/hosts (files) via DNS.

Example 21.9. /etc/nsswitch.conf

passwd:     compat
group:      compat

hosts:      files dns
networks:   files dns

services:   db files
protocols:  db files

netgroup:   files
automount:  files nis

The “databases” available over NSS are listed in Table 21.7, “Databases Available via /etc/nsswitch.conf”. In addition, automount, bootparams, netmasks and publickey are expected in the near future. The configuration options for NSS databases are listed in Table 21.8, “Configuration Options for NSS “Databases””.

Table 21.7. Databases Available via /etc/nsswitch.conf

aliases

Mail aliases implemented by sendmail; see man 5 aliases.

ethers

Ethernet addresses.

group

For user groups used by getgrent. See also the man page for group.

hosts

For hostnames and IP addresses, used by gethostbyname and similar functions.

netgroup

Valid host and user lists in the network for the purpose of controlling access permissions; see the netgroup(5) man page.

networks

Network names and addresses, used by getnetent.

passwd

User passwords, used by getpwent; see the passwd(5) man page.

protocols

Network protocols, used by getprotoent; see the protocols(5) man page.

rpc

Remote procedure call names and addresses, used by getrpcbyname and similar functions.

services

Network services, used by getservent.

shadow

Shadow passwords of users, used by getspnam; see the shadow(5) man page.

Table 21.8. Configuration Options for NSS “Databases”

files

directly access files, for example, /etc/aliases

db

access via a database

nis, nisplus

NIS, see also “Using NIS” (↑Security Guide)

dns

can only be used as an extension for hosts and networks

compat

can only be used as an extension for passwd, shadow and group

/etc/nscd.conf

This file is used to configure nscd (name service cache daemon). See the nscd(8) and nscd.conf(5) man pages. By default, the system entries of passwd and groups are cached by nscd. This is important for the performance of directory services, like NIS and LDAP, because otherwise the network connection needs to be used for every access to names or groups. hosts is not cached by default, because the mechanism in nscd to cache hosts makes the local system unable to trust forward and reverse lookup checks. Instead of asking nscd to cache names, set up a caching DNS server.

If the caching for passwd is activated, it usually takes about fifteen seconds until a newly added local user is recognized. Reduce this waiting time by restarting nscd with the command rcnscd restart.

/etc/HOSTNAME

This contains the hostname without the domain name attached. This file is read by several scripts while the machine is booting. It must contain only one line (in which the hostname is set).

Testing the Configuration

Before you write your configuration to the configuration files, you can test it. To set up a test configuration, use the ip command. To test the connection, use the ping command. Older configuration tools, ifconfig and route, are also available.

The commands ip, ifconfig and route change the network configuration directly without saving it in the configuration file. Unless you enter your configuration in the correct configuration files, the changed network configuration is lost on reboot.

Configuring a Network Interface with ip

ip is a tool to show and configure routing, network devices, policy routing and tunnels.

ip is a very complex tool. Its common syntax is ip options object command. You can work with the following objects:

link

This object represents a network device.

address

This object represents the IP address of device.

neighbour

This object represents a ARP or NDISC cache entry.

route

This object represents the routing table entry.

rule

This object represents a rule in the routing policy database.

maddress

This object represents a multicast address.

mroute

This object represents a multicast routing cache entry.

tunnel

This object represents a tunnel over IP.

If no command is given, the default command is used (usually list).

Change the state of a device with the command ip link set device_name command. For example, to deactivate device eth0, enter ip link set eth0 down. To activate it again, use ip link set eth0 up.

After activating a device, you can configure it. To set the IP address, use ip addr add ip_address + dev device_name. For example, to set the address of the interface eth0 to 192.168.12.154/30 with standard broadcast (option brd), enter ip addr add 192.168.12.154/30 brd + dev eth0.

To have a working connection, you must also configure the default gateway. To set a gateway for your system, enter ip route add gateway_ip_address. To translate one IP address to another, use nat: ip route add nat ip_address via other_ip_address.

To display all devices, use ip link ls. To display the running interfaces only, use ip link ls up. To print interface statistics for a device, enter ip -s link ls device_name. To view addresses of your devices, enter ip addr. In the output of the ip addr, also find information about MAC addresses of your devices. To show all routes, use ip route show.

For more information about using ip, enter ip help or see the ip(8) man page. The help option is also available for all ip objects. If, for example, you want to read help for ip addr, enter ip addr help. Find the ip manual in /usr/share/doc/packages/iproute2/ip-cref.pdf.

Testing a Connection with ping

The ping command is the standard tool for testing whether a TCP/IP connection works. It uses the ICMP protocol to send a small data packet, ECHO_REQUEST datagram, to the destination host, requesting an immediate reply. If this works, ping displays a message to that effect, which indicates that the network link is basically functioning.

ping does more than test only the function of the connection between two computers: it also provides some basic information about the quality of the connection. In Example 21.10, “Output of the Command ping”, you can see an example of the ping output. The second-to-last line contains information about number of transmitted packets, packet loss, and total time of ping running.

As the destination, you can use a hostname or IP address, for example, ping example.com or ping 192.168.3.100. The program sends packets until you press Ctrl+C.

If you only need to check the functionality of the connection, you can limit the number of the packets with the -c option. For example to limit ping to three packets, enter ping -c 3 example.com.

Example 21.10. Output of the Command ping

ping -c 3 example.com
PING example.com (192.168.3.100) 56(84) bytes of data.
64 bytes from example.com (192.168.3.100): icmp_seq=1 ttl=49 time=188 ms
64 bytes from example.com (192.168.3.100): icmp_seq=2 ttl=49 time=184 ms
64 bytes from example.com (192.168.3.100): icmp_seq=3 ttl=49 time=183 ms
--- example.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2007ms
rtt min/avg/max/mdev = 183.417/185.447/188.259/2.052 ms

The default interval between two packets is one second. To change the interval, ping provides option -i. For example to increase ping interval to ten seconds, enter ping -i 10 example.com.

In a system with multiple network devices, it is sometimes useful to send the ping through a specific interface address. To do so, use the -I option with the name of the selected device, for example, ping -I wlan1 example.com.

For more options and information about using ping, enter ping -h or see the ping (8) man page.

Configuring the Network with ifconfig

ifconfig is a traditional network configuration tool. In contrast to ip, you can use it only for interface configuration. If you want to configure routing, use route.

ifconfig and ip

The program ifconfig is obsolete. Use ip instead.

Without arguments, ifconfig displays the status of the currently active interfaces. As you can see in Example 21.11, “Output of the ifconfig Command”, ifconfig has very well-arranged and detailed output. The output also contains information about the MAC address of your device (the value of HWaddr) in the first line.

Example 21.11. Output of the ifconfig Command

eth0      Link encap:Ethernet  HWaddr 00:08:74:98:ED:51
          inet6 addr: fe80::208:74ff:fe98:ed51/64 Scope:Link
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:634735 errors:0 dropped:0 overruns:4 frame:0
          TX packets:154779 errors:0 dropped:0 overruns:0 carrier:1
          collisions:0 txqueuelen:1000
          RX bytes:162531992 (155.0 Mb)  TX bytes:49575995 (47.2 Mb)
          Interrupt:11 Base address:0xec80

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:8559 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8559 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:533234 (520.7 Kb)  TX bytes:533234 (520.7 Kb)

wlan1     Link encap:Ethernet  HWaddr 00:0E:2E:52:3B:1D
          inet addr:192.168.2.4  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: fe80::20e:2eff:fe52:3b1d/64 Scope:Link
          UP BROADCAST NOTRAILERS RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:50828 errors:0 dropped:0 overruns:0 frame:0
          TX packets:43770 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:45978185 (43.8 Mb)  TX bytes:7526693 (7.1 MB)

For more options and information about using ifconfig, enter ifconfig -h or see the ifconfig (8) man page.

Configuring Routing with route

route is a program for manipulating the IP routing table. You can use it to view your routing configuration and add or remove of routes.

route and ip

The program route is obsolete. Use ip instead.

route is especially useful if you need quick and comprehensible information about your routing configuration to determine problems with routing. To view your current routing configuration, enter route -n as root.

Example 21.12. Output of the route -n Command

route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
10.20.0.0       *               255.255.248.0   U         0 0          0 eth0
link-local      *               255.255.0.0     U         0 0          0 eth0
loopback        *               255.0.0.0       U         0 0          0 lo
default         styx.exam.com   0.0.0.0         UG        0 0          0 eth0

For more options and information about using route, enter route -h or see the route (8) man page.

Start-Up Scripts

Apart from the configuration files described above, there are also various scripts that load the network programs while the machine is booting. These are started as soon as the system is switched to one of the multiuser runlevels. Some of these scripts are described in Table 21.9, “Some Start-Up Scripts for Network Programs”.

Table 21.9. Some Start-Up Scripts for Network Programs

/etc/init.d/network

This script handles the configuration of the network interfaces. If the network service was not started, no network interfaces are implemented.

/etc/init.d/xinetd

Starts xinetd. xinetd can be used to make server services available on the system. For example, it can start vsftpd whenever an FTP connection is initiated.

/etc/init.d/rpcbind

Starts the rpcbind utility that converts RPC program numbers to universal addresses. It is needed for RPC services, such as an NFS server.

/etc/init.d/nfsserver

Starts the NFS server.

/etc/init.d/postfix

Controls the postfix process.

/etc/init.d/ypserv

Starts the NIS server.

/etc/init.d/ypbind

Starts the NIS client.

smpppd as Dial-up Assistant

Some home users do not have a dedicated line connecting them to the Internet. Instead, they use dial-up connections. Depending on the dial-up method (ISDN or DSL), the connection is controlled by ipppd or pppd. Basically, all that needs to be done to go online is to start these programs correctly.

If you have a flat-rate connection that does not generate any additional costs for the dial-up connection, simply start the respective daemon. Control the dial-up connection with a desktop applet or a command-line interface. If the Internet gateway is not the host you are using, you might want to control the dial-up connection by way of a network host.

This is where smpppd is involved. It provides a uniform interface for auxiliary programs and acts in two directions. First, it programs the required pppd or ipppd and controls its dial-up properties. Second, it makes various providers available to the user programs and transmits information about the current status of the connection. As smpppd can also be controlled by way of the network, it is suitable for controlling dial-up connections to the Internet from a workstation in a private subnetwork.

Configuring smpppd

The connections provided by smpppd are automatically configured by YaST. The actual dial-up programs KInternet and cinternet are also preconfigured. Manual settings are only required to configure additional features of smpppd such as remote control.

The configuration file of smpppd is /etc/smpppd.conf. By default, it does not enable remote control. The most important options of this configuration file are:

open-inet-socket = yes|no

To control smpppd via the network, set this option to yes. smpppd listens on port 3185. If this parameter is set to yes, the parameters bind-address, host-range and password must be set accordingly.

bind-address = ip address

If a host has several IP addresses, use this parameter to determine at which IP address smpppd should accept connections. The default is to listen at all addresses.

host-range = min ipmax ip

The parameter host-range defines a network range. Hosts whose IP addresses are within this range are granted access to smpppd. All hosts not within this range are denied access.

password = password

By assigning a password, limit the clients to authorized hosts. As this is a plain-text password, you should not overrate the security it provides. If no password is assigned, all clients are permitted to access smpppd.

slp-register = yes|no

With this parameter, the smpppd service can be announced in the network via SLP.

More information about smpppd is available in the smpppd(8) and smpppd.conf(5) man pages.

Configuring KInternet and cinternet for Remote Use

KInternet and cinternet can be used to control a local or remote smpppd. cinternet is the command-line counterpart of the graphical KInternet. To prepare these utilities for use with a remote smpppd, edit the configuration file /etc/smpppd-c.conf manually or using KInternet. This file only uses four options:

sites = list of sites

list of sites where the front-ends search for smpppd. The front-ends test the options in the order specified here. local orders the establishment of a connection to the local smpppd. gateway points to an smpppd on the gateway. config-file indicates that the connection should be established to the smpppd specified in the server and port options in /etc/smpppd-c.conf. slp orders the front-ends to connect to an smpppd found via SLP.

server = server

The host on which smpppd runs.

port = port

The port on which smpppd runs.

password = password

The password selected for smpppd.

If smpppd is active, try to access it. For example, with cinternet --verbose --interface-list. In case of difficulties at this point, refer to the smpppd-c.conf(5) and cinternet(8) man pages.

Chapter 22. SLP Services in the Network

Abstract

The service location protocol (SLP) was developed to simplify the configuration of networked clients within a local network. To configure a network client, including all required services, the administrator traditionally needs detailed knowledge of the servers available in the network. SLP makes the availability of selected services known to all clients in the local network. Applications that support SLP can use the information distributed and be configured automatically.

openSUSE® supports installation using installation sources provided with SLP and contains many system services with integrated support for SLP. YaST and Konqueror both have appropriate front-ends for SLP. You can use SLP to provide networked clients with central functions, such as an installation server, file server, or print server on your system.

SLP Support in openSUSE

Services that offer SLP support include cupsd, rsyncd, ypserv, openldap2, ksysguardd, saned, kdm, vnc, login, smpppd, rpasswd, postfix, and sshd (via fish).

Installation

Only an SLP client and slptools are installed by default. If you want to provide services via SLP, install the package openslp-server. To install the package, start YaST and select Software+Software Management. Now choose Filter+Patterns and click Misc. Server. Select openslp-server. Confirm the installation of the required packages to finish the installation process.

Activating SLP

slpd must run on your system to offer services with SLP. If the machine should only operate as client, and does not offer services, it is not necessary to run slpd. Like most system services in openSUSE, the slpd daemon is controlled by means of a separate init script. After the installation, the daemon is inactive by default. To activate it temporarily, run rcslpd start as root or rcslpd stop to stop it. Perform a restart or status check with restart or status. If slpd should be always active after booting, enable slpd in YaST System+System Services (Runlevel) or run the insserv slpd command as root. This includes slpd in the set of services to be started at boot time.

SLP Front-Ends in openSUSE

To find services provided via SLP in your network, use an SLP front-end. openSUSE contains several front-ends:

slptool

slptool is a simple command line program that can be used to announce SLP inquiries in the network or announce proprietary services. slptool --help lists all available options and functions. slptool can also be called from scripts that process SLP information. For example, to find all network time servers that annouce themselves in the current network, run the command:

slptool findsrvs service:ntp

YaST

Within YaST there is also a SLP browser available. However, this browser is not available through the YaST Control Center. To start this YaST module, run yast2 slp as root user. Click on the different protocols on the lefthand side of the user interface to get more information about the respective service.

Installation over SLP

If you offer an installation server with openSUSE installation media within your network, this can be registered with SLP. For details, see Section “Setting Up the Server Holding the Installation Sources”. If SLP installation is selected, linuxrc starts an SLP inquiry after the system has booted from the selected boot medium and displays the sources found.

Providing Services via SLP

Many applications in openSUSE have integrated SLP support through the use of the libslp library. If a service has not been compiled with SLP support, use one of the following methods to make it available via SLP:

Static Registration with /etc/slp.reg.d

Create a separate registration file for each new service. The following is an example of a file for registering a scanner service:

## Register a saned service on this system
## en means english language
## 65535 disables the timeout, so the service registration does
## not need refreshes
service:scanner.sane://$HOSTNAME:6566,en,65535
watch-port-tcp=6566
description=SANE scanner daemon

The most important line in this file is the service URL, which begins with service:. This contains the service type (scanner.sane) and the address under which the service is available on the server. $HOSTNAME is automatically replaced with the full hostname. The name of the TCP port on which the relevant service can be found follows, separated by a colon. Then enter the language in which the service should appear and the duration of registration in seconds. These should be separated from the service URL by commas. Set the value for the duration of registration between 0 and 65535. 0 prevents registration. 65535 removes all restrictions.

The registration file also contains the two variables watch-port-tcp and description. watch-port-tcp links the SLP service announcement to whether the relevant service is active by having slpd check the status of the service. The second variable contains a more precise description of the service that is displayed in suitable browsers.

Static Registration with /etc/slp.reg

The only difference between this method and the procedure with /etc/slp.reg.d is that all services are grouped within a central file.

Dynamic Registration with slptool

If a service needs to be registered dynamically without the need of configuration files, use the slptool command line utility. The same utility can also be used to deregister an existing service offering without restarting slpd.

For More Information

The following sources provide further information about SLP:

RFC 2608, 2609, 2610

RFC 2608 generally deals with the definition of SLP. RFC 2609 deals with the syntax of the service URLs used in greater detail and RFC 2610 deals with DHCP via SLP.

http://www.openslp.org/

The home page of the OpenSLP project.

/usr/share/doc/packages/openslp

This directory contains all available documentation for SLP, including a README.SuSE containing the openSUSE details, the RFCs, and two introductory HTML documents. Programmers who want to use the SLP functions find more information in the Programmers Guide that is included in the openslp-devel package.

Chapter 23. The Domain Name System

Abstract

DNS (domain name system) is needed to resolve the domain names and hostnames into IP addresses. In this way, the IP address 192.168.2.100 is assigned to the hostname jupiter, for example. Before setting up your own name server, read the general information about DNS in Section “Name Resolution”. The following configuration examples refer to BIND.

DNS Terminology

Zone

The domain namespace is divided into regions called zones. For instance, if you have example.com, you have the example section (or zone) of the com domain.

DNS server

The DNS server is a server that maintains the name and IP information for a domain. You can have a primary DNS server for master zone, a secondary server for slave zone, or a slave server without any zones for caching.

Master zone DNS server

The master zone includes all hosts from your network and a DNS server master zone stores up-to-date records for all the hosts in your domain.

Slave zone DNS server

A slave zone is a copy of the master zone. The slave zone DNS server obtains its zone data with zone transfer operations from its master server. The slave zone DNS server responds authoritatively for the zone as long as it has valid (not expired) zone data. If the slave cannot obtain a new copy of the zone data, it stops responding for the zone.

Forwarder

Forwarders are DNS servers to which your DNS server should send queries it cannot answer. To enable different configuration sources in one configuration, netconfig is used (see also man 8 netconfig).

Record

The record is information about name and IP address. Supported records and their syntax are described in BIND documentation. Some special records are:

NS record

An NS record tells name servers which machines are in charge of a given domain zone.

MX record

The MX (mail exchange) records describe the machines to contact for directing mail across the Internet.

SOA record

SOA (Start of Authority) record is the first record in a zone file. The SOA record is used when using DNS to synchronize data between multiple computers.

Installation

To install a DNS server, start YaST and select Software+Software Management. Choose Filter+Patterns and select DHCP and DNS Server. Confirm the installation of the dependent packages to finish the installation process.

Configuration with YaST

You can use the DNS module of YaST to configure a DNS server for your local network. When starting the module for the first time, a wizard starts, prompting you to make just a few basic decisions concerning administration of the server. Completing this initial setup produces a very basic server configuration that should be functioning in its essential aspects. The expert mode can be used to deal with more advanced configuration tasks.

Wizard Configuration

The wizard consists of three steps or dialogs. At the appropriate places in the dialogs, you are given the opportunity to enter the expert configuration mode.

When starting the module for the first time, the Forwarder Settings dialog, shown in Figure 23.1, “DNS Server Installation: Forwarder Settings”, opens. The Netconfig DNS Policy decides which devices should provide forwarders or whether you want to supply your own Forwarder List. For more information about netconfig, see man 8 netconfig.

Figure 23.1. DNS Server Installation: Forwarder Settings

The DNS Zones dialog consists of several parts and is responsible for the management of zone files, described in Section “Zone Files”. For a new zone, provide a name for it in Zone Name. To add a reverse zone, the name must end in .in-addr.arpa. Finally, select the Zone Type (master or slave). See Figure 23.2, “DNS Server Installation: DNS Zones”. Click Edit Zone to configure other settings of an existing zone. To remove a zone, click Delete Zone.

Figure 23.2. DNS Server Installation: DNS Zones

In the final dialog, you can open the DNS port in the firewall by clicking Open Port in Firewall. Then decide whether or not the DNS server should be started (On or Off). You can also activate LDAP support. See Figure 23.3, “DNS Server Installation: Finish Wizard”.

Figure 23.3. DNS Server Installation: Finish Wizard

Expert Configuration

After starting the module, YaST opens a window displaying several configuration options. Completing it results in a DNS server configuration with the basic functions in place:

Start-Up

Under Start-Up, define whether the DNS server should be started on startup (during the booting the system) or manually. To start the DNS server immediately, select Start DNS Server Now. To stop the DNS server, select Stop DNS Server Now. To save the current settings, select Save Settings and Restart DNS Server Now. You can open the DNS port in the firewall with Open Port in Firewall and modify the firewall settings with Firewall Details.

By selecting LDAP Support Active, the zone files are managed by an LDAP database. Any changes to zone data written to the LDAP database are picked up by the DNS server as soon as it is restarted or prompted to reload its configuration.

Forwarders

If your local DNS server cannot answer a request, it tries to forward the request to a Forwarder, if configured so. This forwarder may be added manually to the Forwarder List. If the forwarder is not static like in dial-up connections, netconfig handles the configuration. For more information about netconfig, see man 8 netconfig.

Basic Options

In this section, set basic server options. From the Option menu, select the desired item then specify the value in the corresponding entry field. Include the new entry by selecting Add.

Logging

To set what the DNS server should log and how, select Logging. Under Log Type, specify where the DNS server should write the log data. Use the systemwide log file /var/log/messages by selecting System Log or specify a different file by selecting File. In the latter case, additionally specify a name, the maximum file size in megabytes and the number of logfile versions to store.

Further options are available under Additional Logging. Enabling Log All DNS Queries causes every query to be logged, in which case the log file could grow extremely large. For this reason, it is not a good idea to enable this option for other than debugging purposes. To log the data traffic during zone updates between DHCP and DNS server, enable Log Zone Updates. To log the data traffic during a zone transfer from master to slave, enable Log Zone Transfer. See Figure 23.4, “DNS Server: Logging”.

Figure 23.4. DNS Server: Logging

Using ACLs

Use this window to define ACLs (access control lists) to enforce access restrictions. After providing a distinct name under Name, specify an IP address (with or without netmask) under Value in the following fashion:

{ 192.168.1/24; }

The syntax of the configuration file requires that the address ends with a semicolon and is put into curly braces.

TSIG Keys

The main purpose of TSIGs (transaction signatures) is to secure communications between DHCP and DNS servers. They are described in Section “Secure Transactions”.

To generate a TSIG key, enter a distinctive name in the field labeled Key ID and specify the file where the key should be stored (Filename). Confirm your choices with Add.

To use a previously created key, leave the Key ID field blank and select the file where it is stored under File Name. After that, confirm with Add.

Adding a Slave Zone

To add a slave zone, select DNS Zones, choose the zone type Slave, write the name of the new zone, and click Add.

In the Zone Editor under Master DNS Server IP, specify the master from which the slave should pull its data. To limit access to the server, select one of the ACLs from the list.

Adding a Master Zone

To add a master zone, select DNS Zones, choose the zone type Master, write the name of the new zone, and click Add. When adding a master zone, a reverse zone is also needed. For example, when adding the zone example.com that points to hosts in a subnet 192.168.1.0/24, you should also add a reverse zone for the IP-address range covered. By definition, this should be named 1.168.192.in-addr.arpa.

Editing a Master Zone

To edit a master zone, select DNS Zones, select the master zone from the table, and click Edit. The dialog consists of several pages: Basics (the one opened first), NS Records, MX Records, SOA, and Records.

In the basic dialog, select whether to enable zone transfers. Use the listed ACLs to define who can download zones.

Zone Editor (NS Records)

This dialog allows you to define alternative name servers for the zones specified. Make sure that your own name server is included in the list. To add a record, enter its name under Name Server to Add then confirm with Add. See Figure 23.5, “DNS Server: Zone Editor (NS Records)”.

Figure 23.5. DNS Server: Zone Editor (NS Records)

Zone Editor (MX Records)

To add a mail server for the current zone to the existing list, enter the corresponding address and priority value. After doing so, confirm by selecting Add. See Figure 23.6, “DNS Server: Zone Editor (MX Records)”.

Figure 23.6. DNS Server: Zone Editor (MX Records)

Zone Editor (SOA)

This page allows you to create SOA (start of authority) records. For an explanation of the individual options, refer to Example 23.6, “File /var/lib/named/example.com.zone”.

Figure 23.7. DNS Server: Zone Editor (SOA)

Zone Editor (Records)

This dialog manages name resolution. In Record Key, enter the hostname then select its type. A-Record represents the main entry. The value for this should be an IP address. CNAME is an alias. Use the types NS and MX for detailed or partial records that expand on the information provided in the NS Records and MX Records tabs. These three types resolve to an existing A record. PTR is for reverse zones. It is the opposite of an A record, for example:

hostname.example.com. IN A 192.168.0.1
1.0.168.192.in-addr.arpa IN PTR hostname.example.com.

Editing the Reverse Zone

After adding a forward zone, go back to the main menu and select the reverse zone for editing. There in the tab Basics activate the checkbox Automatically Generate Records From and select your forward zone. That way, all changes to the forward zone are automatically updated in the reverse zone.

Starting the Name Server BIND

On a openSUSE® system, the name server BIND (Berkeley Internet Name Domain) comes preconfigured so it can be started right after installation without any problem. If you already have a functioning Internet connection and have entered 127.0.0.1 as the name server address for localhost in /etc/resolv.conf, you normally already have a working name resolution without needing to know the DNS of the provider. BIND carries out name resolution via the root name server, a notably slower process. Normally, the DNS of the provider should be entered with its IP address in the configuration file /etc/named.conf under forwarders to ensure effective and secure name resolution. If this works so far, the name server runs as a pure caching-only name server. Only when you configure its own zones will it become a proper DNS. A simple example of this is included in the documentation in /usr/share/doc/packages/bind/config.

Automatic Adaptation of the Name Server Information

Depending on the type of Internet connection or the network connection, the name server information can automatically be adapted to the current conditions. To do this, set the variable MODIFY_NAMED_CONF_DYNAMICALLY in the file /etc/sysconfig/network/config to yes.

However, do not set up any official domains until assigned one by the responsible institution. Even if you have your own domain and it is managed by the provider, you are better off not using it, because BIND would otherwise not forward requests for this domain. The Web server at the provider, for example, would not be accessible for this domain.

To start the name server, enter the command rcnamed start as root. If “done” appears to the right in green then named (as the name server process is called) has been started successfully. Test the name server immediately on the local system with the host or dig programs, which should return localhost as the default server with the address 127.0.0.1. If this is not the case, /etc/resolv.conf probably contains an incorrect name server entry or the file does not exist at all. For the first test, enter host 127.0.0.1, which should always work. If you get an error message, use rcnamed status to see whether the server is actually running. If the name server does not start or behaves unexpectedly, you can usually find the cause in the log file /var/log/messages.

To use the name server of the provider (or one already running on your network) as the forwarder, enter the corresponding IP address or addresses in the options section under forwarders. The addresses included in Example 23.1, “Forwarding Options in named.conf” are just examples. Adjust these entries to your own setup.

Example 23.1. Forwarding Options in named.conf

options {
        directory "/var/lib/named";
        forwarders { 10.11.12.13; 10.11.12.14; };
        listen-on { 127.0.0.1; 192.168.1.116; };
        allow-query { 127/8; 192.168/16 };
        notify no;
        };

The options entry is followed by entries for the zone, localhost, and 0.0.127.in-addr.arpa. The type hint entry under “.” should always be present. The corresponding files do not need to be modified and should work as they are. Also make sure that each entry is closed with a “;” and that the curly braces are in the correct places. After changing the configuration file /etc/named.conf or the zone files, tell BIND to reread them with rcnamed reload. Achieve the same by stopping and restarting the name server with rcnamed restart. Stop the server at any time by entering rcnamed stop.

The Configuration File /etc/named.conf

All the settings for the BIND name server itself are stored in the file /etc/named.conf. However, the zone data for the domains to handle (consisting of the hostnames, IP addresses, and so on) are stored in separate files in the /var/lib/named directory. The details of this are described later.

/etc/named.conf is roughly divided into two areas. One is the options section for general settings and the other consists of zone entries for the individual domains. A logging section and acl (access control list) entries are optional. Comment lines begin with a # sign or //. A minimal /etc/named.conf is shown in Example 23.2, “A Basic /etc/named.conf”.

Example 23.2. A Basic /etc/named.conf

options {
        directory "/var/lib/named";
        forwarders { 10.0.0.1; };
        notify no;
};

zone "localhost" in {
       type master;
       file "localhost.zone";
};

zone "0.0.127.in-addr.arpa" in {
        type master;
        file "127.0.0.zone";
};

zone "." in {
        type hint;
        file "root.hint";
};

Important Configuration Options

directory "filename";

Specifies the directory in which BIND can find the files containing the zone data. Usually, this is /var/lib/named.

forwarders { ip-address; };

Specifies the name servers (mostly of the provider) to which DNS requests should be forwarded if they cannot be resolved directly. Replace ip-address with an IP address like 192.168.1.116.

forward first;

Causes DNS requests to be forwarded before an attempt is made to resolve them via the root name servers. Instead of forward first, forward only can be written to have all requests forwarded and none sent to the root name servers. This makes sense for firewall configurations.

listen-on port 53 { 127.0.0.1; ip-address; };

Tells BIND on which network interfaces and port to accept client queries. port 53 does not need to be specified explicitly, because 53 is the default port. Enter 127.0.0.1 to permit requests from the local host. If you omit this entry entirely, all interfaces are used by default.

listen-on-v6 port 53 {any; };

Tells BIND on which port it should listen for IPv6 client requests. The only alternative to any is none. As far as IPv6 is concerned, the server only accepts wild card addresses.

query-source address * port 53;

This entry is necessary if a firewall is blocking outgoing DNS requests. This tells BIND to post requests externally from port 53 and not from any of the high ports above 1024.

query-source-v6 address * port 53;

Tells BIND which port to use for IPv6 queries.

allow-query { 127.0.0.1; net; };

Defines the networks from which clients can post DNS requests. Replace net with address information like 192.168.2.0/24. The /24 at the end is an abbreviated expression for the netmask (in this case 255.255.255.0).

allow-transfer ! *;;

Controls which hosts can request zone transfers. In the example, such requests are completely denied with ! *. Without this entry, zone transfers can be requested from anywhere without restrictions.

statistics-interval 0;

In the absence of this entry, BIND generates several lines of statistical information per hour in /var/log/messages. Set it to 0 to suppress these statistics completely or set an interval in minutes.

cleaning-interval 720;

This option defines at which time intervals BIND clears its cache. This triggers an entry in /var/log/messages each time it occurs. The time specification is in minutes. The default is 60 minutes.

interface-interval 0;

BIND regularly searches the network interfaces for new or nonexistent interfaces. If this value is set to 0, this is not done and BIND only listens at the interfaces detected at start-up. Otherwise, the interval can be defined in minutes. The default is sixty minutes.

notify no;

no prevents other name servers from being informed when changes are made to the zone data or when the name server is restarted.

For a list of available options, read the manual page man 5 named.conf.

Logging

What, how, and where logging takes place can be extensively configured in BIND. Normally, the default settings should be sufficient. Example 23.3, “Entry to Disable Logging”, shows the simplest form of such an entry and completely suppresses any logging.

Example 23.3. Entry to Disable Logging

logging {
        category default { null; };
};

Zone Entries

Example 23.4. Zone Entry for example.com

zone "example.com" in {
      type master;
      file "example.com.zone";
      notify no;
};

After zone, specify the name of the domain to administer (example.com) followed by in and a block of relevant options enclosed in curly braces, as shown in Example 23.4, “Zone Entry for example.com”. To define a slave zone, switch the type to slave and specify a name server that administers this zone as master (which, in turn, may be a slave of another master), as shown in Example 23.5, “Zone Entry for example.net”.

Example 23.5. Zone Entry for example.net

zone "example.net" in {
      type slave;
      file "slave/example.net.zone";
      masters { 10.0.0.1; };
};

The zone options:

type master;

By specifying master, tell BIND that the zone is handled by the local name server. This assumes that a zone file has been created in the correct format.

type slave;

This zone is transferred from another name server. It must be used together with masters.

type hint;

The zone . of the hint type is used to set the root name servers. This zone definition can be left as is.

file example.com.zone or file “slave/example.net.zone”;

This entry specifies the file where zone data for the domain is located. This file is not required for a slave, because this data is pulleds from another name server. To differentiate master and slave files, use the directory slave for the slave files.

masters { server-ip-address; };

This entry is only needed for slave zones. It specifies from which name server the zone file should be transferred.

allow-update {! *; };

This option controls external write access, which would allow clients to make a DNS entry—something not normally desirable for security reasons. Without this entry, zone updates are not allowed at all. The above entry achieves the same because ! * effectively bans any such activity.

Zone Files

Two types of zone files are needed. One assigns IP addresses to hostnames and the other does the reverse: it supplies a hostname for an IP address.

Using the Dot (Period, Fullstop) in Zone Files

The "." has an important meaning in the zone files. If hostnames are given without a final ., the zone is appended. Complete hostnames specified with a full domain name must end with a . to avoid having the domain added to it again. A missing or wrongly placed "." is probably the most frequent cause of name server configuration errors.

The first case to consider is the zone file example.com.zone, responsible for the domain example.com, shown in Example 23.6, “File /var/lib/named/example.com.zone”.

Example 23.6. File /var/lib/named/example.com.zone

1.  $TTL 2D
2.  example.com. IN SOA      dns  root.example.com. (
3.               2003072441  ; serial
4.               1D          ; refresh
5.               2H          ; retry
6.               1W          ; expiry
7.               2D )        ; minimum
8.
9.               IN NS       dns
10.              IN MX       10 mail
11.
12. gate         IN A        192.168.5.1
13.              IN A        10.0.0.1
14. dns          IN A        192.168.1.116
15. mail         IN A        192.168.3.108
16. jupiter      IN A        192.168.2.100
17. venus        IN A        192.168.2.101
18. saturn       IN A        192.168.2.102
19. mercury      IN A        192.168.2.103
20. ntp          IN CNAME    dns
21. dns6         IN A6  0    2002:c0a8:174::

Line 1:

$TTL defines the default time to live that should apply to all the entries in this file. In this example, entries are valid for a period of two days (2 D).

Line 2:

This is where the SOA (start of authority) control record begins:

The name of the domain to administer is example.com in the first position. This ends with ".", because otherwise the zone would be appended a second time. Alternatively, @ can be entered here, in which case the zone would be extracted from the corresponding entry in /etc/named.conf.

After IN SOA is the name of the name server in charge as master for this zone. The name is expanded from dns to dns.example.com, because it does not end with a ".".

An e-mail address of the person in charge of this name server follows. Because the @ sign already has a special meaning, "." is entered here instead. For root@example.com the entry must read root.example.com.. The "." must be included at the end to prevent the zone from being added.

The ( includes all lines up to ) into the SOA record.

Line 3:

The serial number is an arbitrary number that is increased each time this file is changed. It is needed to inform the secondary name servers (slave servers) of changes. For this, a 10 digit number of the date and run number, written as YYYYMMDDNN, has become the customary format.

Line 4:

The refresh rate specifies the time interval at which the secondary name servers verify the zone serial number. In this case, one day.

Line 5:

The retry rate specifies the time interval at which a secondary name server, in case of error, attempts to contact the primary server again. Here, two hours.

Line 6:

The expiration time specifies the time frame after which a secondary name server discards the cached data if it has not regained contact to the primary server. Here, a week.

Line 7:

The last entry in the SOA record specifies the negative caching TTL—the time for which results of unresolved DNS queries from other servers may be cached.

Line 9:

The IN NS specifies the name server responsible for this domain. dns is extended to dns.example.com because it does not end with a ".". There can be several lines like this—one for the primary and one for each secondary name server. If notify is not set to no in /etc/named.conf, all the name servers listed here are informed of the changes made to the zone data.

Line 10:

The MX record specifies the mail server that accepts, processes, and forwards e-mails for the domain example.com. In this example, this is the host mail.example.com. The number in front of the hostname is the preference value. If there are multiple MX entries, the mail server with the smallest value is taken first and, if mail delivery to this server fails, an attempt is made with the next higher value.

Lines 12–19:

These are the actual address records where one or more IP addresses are assigned to hostnames. The names are listed here without a "." because they do not include their domain, so example.com is added to all of them. Two IP addresses are assigned to the host gate, as it has two network cards. Wherever the host address is a traditional one (IPv4), the record is marked with A. If the address is an IPv6 address, the entry is marked with AAAA.

IPv6 Syntax

The IPv6 record has a slightly different syntax than IPv4. Because of the fragmentation possibility, it is necessary to provide information about missed bits before the address. To just fill up the IPv6 address with the needed number of “0”, add two colons at the correct place in the address.

pluto     AAAA 2345:00C1:CA11::1234:5678:9ABC:DEF0
pluto     AAAA 2345:00D2:DA11::1234:5678:9ABC:DEF0

Line 20:

The alias ntp can be used to address dns (CNAME means canonical name).

The pseudodomain in-addr.arpa is used for the reverse lookup of IP addresses into hostnames. It is appended to the network part of the address in reverse notation. So 192.168 is resolved into 168.192.in-addr.arpa. See Example 23.7, “Reverse Lookup”.

Example 23.7. Reverse Lookup

1.  $TTL 2D
2.  168.192.in-addr.arpa.   IN SOA dns.example.com. root.example.com. (
3.                          2003072441      ; serial
4.                          1D              ; refresh
5.                          2H              ; retry
6.                          1W              ; expiry
7.                          2D )            ; minimum
8.
9.                          IN NS           dns.example.com.
10.
11. 1.5                     IN PTR          gate.example.com.
12. 100.3                   IN PTR          www.example.com.
13. 253.2                   IN PTR          cups.example.com.

Line 1:

$TTL defines the standard TTL that applies to all entries here.

Line 2:

The configuration file should activate reverse lookup for the network 192.168. Given that the zone is called 168.192.in-addr.arpa, it should not be added to the hostnames. Therefore, all hostnames are entered in their complete form—with their domain and with a "." at the end. The remaining entries correspond to those described for the previous example.com example.

Lines 3–7:

See the previous example for example.com.

Line 9:

Again this line specifies the name server responsible for this zone. This time, however, the name is entered in its complete form with the domain and a "." at the end.

Lines 11–13:

These are the pointer records hinting at the IP addresses on the respective hosts. Only the last part of the IP address is entered at the beginning of the line, without the "." at the end. Appending the zone to this (without the .in-addr.arpa) results in the complete IP address in reverse order.

Normally, zone transfers between different versions of BIND should be possible without any problem.

Dynamic Update of Zone Data

The term dynamic update refers to operations by which entries in the zone files of a master server are added, changed, or deleted. This mechanism is described in RFC 2136. Dynamic update is configured individually for each zone entry by adding an optional allow-update or update-policy rule. Zones to update dynamically should not be edited by hand.

Transmit the entries to update to the server with the command nsupdate. For the exact syntax of this command, check the manual page for nsupdate (man 8 nsupdate). For security reasons, any such update should be performed using TSIG keys as described in Section “Secure Transactions”.

Secure Transactions

Secure transactions can be made with the help of transaction signatures (TSIGs) based on shared secret keys (also called TSIG keys). This section describes how to generate and use such keys.

Secure transactions are needed for communication between different servers and for the dynamic update of zone data. Making the access control dependent on keys is much more secure than merely relying on IP addresses.

Generate a TSIG key with the following command (for details, see man dnssec-keygen):

dnssec-keygen -a hmac-md5 -b 128 -n HOST host1-host2

This creates two files with names similar to these:

Khost1-host2.+157+34265.private Khost1-host2.+157+34265.key

The key itself (a string like ejIkuCyyGJwwuN3xAteKgg==) is found in both files. To use it for transactions, the second file (Khost1-host2.+157+34265.key) must be transferred to the remote host, preferably in a secure way (using scp, for example). On the remote server, the key must be included in the file /etc/named.conf to enable a secure communication between host1 and host2:

key host1-host2 {
 algorithm hmac-md5;
 secret "ejIkuCyyGJwwuN3xAteKgg==";
};

File Permissions of /etc/named.conf

Make sure that the permissions of /etc/named.conf are properly restricted. The default for this file is 0640, with the owner being root and the group named. As an alternative, move the keys to an extra file with specially limited permissions, which is then included from /etc/named.conf. To include an external file, use:

include  "filename"

Replace filename with an absolute path to your file with keys.

To enable the server host1 to use the key for host2 (which has the address 10.1.2.3 in this example), the server's /etc/named.conf must include the following rule:

server 10.1.2.3 {
  keys { host1-host2. ;};
};

Analogous entries must be included in the configuration files of host2.

Add TSIG keys for any ACLs (access control lists, not to be confused with file system ACLs) that are defined for IP addresses and address ranges to enable transaction security. The corresponding entry could look like this:

allow-update { key host1-host2. ;};

This topic is discussed in more detail in the BIND Administrator Reference Manual under update-policy.

DNS Security

DNSSEC, or DNS security, is described in RFC 2535. The tools available for DNSSEC are discussed in the BIND Manual.

A zone considered secure must have one or several zone keys associated with it. These are generated with dnssec-keygen, just like the host keys. The DSA encryption algorithm is currently used to generate these keys. The public keys generated should be included in the corresponding zone file with an $INCLUDE rule.

With the command dnssec-makekeyset, all keys generated are packaged into one set, which must then be transferred to the parent zone in a secure manner. On the parent, the set is signed with dnssec-signkey. The files generated by this command are then used to sign the zones with dnssec-signzone, which in turn generates the files to include for each zone in /etc/named.conf.

For More Information

For additional information, refer to the BIND Administrator Reference Manual from package bind-doc, which is installed under /usr/share/doc/packages/bind/. Consider additionally consulting the RFCs referenced by the manual and the manual pages included with BIND. /usr/share/doc/packages/bind/README.SuSE contains up-to-date information about BIND in openSUSE.

Chapter 24. DHCP

Abstract

The purpose of the dynamic host configuration protocol (DHCP) is to assign network settings centrally (from a server) rather than configuring them locally on each and every workstation. A host configured to use DHCP does not have control over its own static address. It is enabled to configure itself completely and automatically according to directions from the server. If you use the NetworkManager on the client side, you do not need to configure the client at all. This is useful if you have changing environments and only one interface active at a time. Never use NetworkManager on a machine that runs a DHCP server.

One way to configure a DHCP server is to identify each client using the hardware address of its network card (which should be fixed in most cases), then supply that client with identical settings each time it connects to the server. DHCP can also be configured to assign addresses to each relevant client dynamically from an address pool set up for this purpose. In the latter case, the DHCP server tries to assign the same address to the client each time it receives a request, even over extended periods. This works only if the network does not have more clients than addresses.

DHCP makes life easier for system administrators. Any changes, even bigger ones, related to addresses and the network configuration in general can be implemented centrally by editing the server's configuration file. This is much more convenient than reconfiguring numerous workstations. It is also much easier to integrate machines, particularly new machines, into the network, because they can be given an IP address from the pool. Retrieving the appropriate network settings from a DHCP server is especially useful in the case of laptops regularly used in different networks.

In this chapter, the DHCP server will run in the same subnet as the workstations, 192.168.2.0/24 with 192.168.2.1 as gateway. It has the fixed IP address 192.168.2.254 and serves two address ranges, 192.168.2.10 to 192.168.2.20 and 192.168.2.100 192.168.2.200;.

A DHCP server supplies not only the IP address and the netmask, but also the hostname, domain name, gateway, and name server addresses for the client to use. In addition to that, DHCP allows a number of other parameters to be configured in a centralized way, for example, a time server from which clients may poll the current time or even a print server.

Configuring a DHCP Server with YaST

LDAP Support

In this version of openSUSE, the YaST DHCP module can be set up to store the server configuration locally (on the host that runs the DHCP server) or to have its configuration data managed by an LDAP server. If you want to use LDAP, set up your LDAP environment before configuring the DHCP server.

The YaST DHCP module allows you to set up your own DHCP server for the local network. The module can run in simple mode or expert mode.

Initial Configuration (Wizard)

When the module is started for the first time, a wizard starts, prompting you to make a few basic decisions concerning server administration. Completing this initial setup produces a very basic server configuration that should function in its essential aspects. The expert mode can be used to deal with more advanced configuration tasks.

Card Selection

In the first step, YaST looks for the network interfaces available on your system, then displays them in a list. From the list, select the interface on which the DHCP server should listen and click Add. After this, select Open Firewall for Selected Interfaces to open the firewall for this interface. See Figure 24.1, “DHCP Server: Card Selection”.

Figure 24.1. DHCP Server: Card Selection

Global Settings

Use the check box to determine whether your DHCP settings should be automatically stored by an LDAP server. In the entry fields, provide the network specifics for all clients the DHCP server should manage. These specifics are the domain name, address of a time server, addresses of the primary and secondary name server, addresses of a print and a WINS server (for a mixed network with both Windows and Linux clients), gateway address, and lease time. See Figure 24.2, “DHCP Server: Global Settings”.

Figure 24.2. DHCP Server: Global Settings

Dynamic DHCP

In this step, configure how dynamic IP addresses should be assigned to clients. To do so, specify an IP range from which the server can assign addresses to DHCP clients. All these addresses must be covered by the same netmask. Also specify the lease time during which a client may keep its IP address without needing to request an extension of the lease. Optionally, specify the maximum lease time—the period during which the server reserves an IP address for a particular client. See Figure 24.3, “DHCP Server: Dynamic DHCP”.

Figure 24.3. DHCP Server: Dynamic DHCP

Finishing the Configuration and Setting the Start Mode

After the third part of the configuration wizard, a last dialog is shown in which you can define how the DHCP server should be started. Here, specify whether to start the DHCP server automatically when the system is booted or manually when needed (for example, for test purposes). Click Finish to complete the configuration of the server. See Figure 24.4, “DHCP Server: Start-Up”.

Figure 24.4. DHCP Server: Start-Up

DHCP Software Packages

Both the DHCP server and the DHCP clients are available for openSUSE. The DHCP server available is dhcpd (published by the Internet Systems Consortium). On the client side, choose between two different DHCP client programs: dhcp-client (also from ISC) and the DHCP client daemon in the dhcpcd package.

openSUSE installs dhcpcd by default. The program is very easy to handle and is launched automatically on each system boot to watch for a DHCP server. It does not need a configuration file to do its job and works out of the box in most standard setups. For more complex situations, use the ISC dhcp-client, which is controlled by means of the configuration file /etc/dhclient.conf.

The DHCP Server dhcpd

The core of any DHCP system is the dynamic host configuration protocol daemon. This server leases addresses and watches how they are used, according to the settings defined in the configuration file /etc/dhcpd.conf. By changing the parameters and values in this file, a system administrator can influence the program's behavior in numerous ways. Look at the basic sample /etc/dhcpd.conf file in Example 24.1, “The Configuration File /etc/dhcpd.conf”.

Example 24.1. The Configuration File /etc/dhcpd.conf

default-lease-time 600;         # 10 minutes
max-lease-time 7200;            # 2  hours

option domain-name "example.com";
option domain-name-servers 192.168.1.116;
option broadcast-address 192.168.2.255;
option routers 192.168.2.1;
option subnet-mask 255.255.255.0;

subnet 192.168.2.0 netmask 255.255.255.0
 {
  range 192.168.2.10 192.168.2.20;
  range 192.168.2.100 192.168.2.200;
 }

This simple configuration file should be sufficient to get the DHCP server to assign IP addresses in the network. Make sure that a semicolon is inserted at the end of each line, because otherwise dhcpd is not started.

The sample file can be divided into three sections. The first one defines how many seconds an IP address is leased to a requesting client by default (default-lease-time) before it should apply for renewal. This section also includes a statement of the maximum period for which a machine may keep an IP address assigned by the DHCP server without applying for renewal (max-lease-time).

In the second part, some basic network parameters are defined on a global level:

The line option domain-name defines the default domain of your network.

With the entry option domain-name-servers, specify up to three values for the DNS servers used to resolve IP addresses into hostnames and vice versa. Ideally, configure a name server on your machine or somewhere else in your network before setting up DHCP. That name server should also define a hostname for each dynamic address and vice versa. To learn how to configure your own name server, read Chapter 23, The Domain Name System.

The line option broadcast-address defines the broadcast address the requesting client should use.

With option routers, set where the server should send data packets that cannot be delivered to a host on the local network (according to the source and target host address and the subnet mask provided). In most cases, especially in smaller networks, this router is identical to the Internet gateway.

With option subnet-mask, specify the netmask assigned to clients.

The last section of the file defines a network, including a subnet mask. To finish, specify the address range that the DHCP daemon should use to assign IP addresses to interested clients. In Example 24.1, “The Configuration File /etc/dhcpd.conf”, clients may be given any address between 192.168.2.10 and 192.168.2.20 as well as 192.168.2.100 and 192.168.2.200.

After editing these few lines, you should be able to activate the DHCP daemon with the command rcdhcpd start. It will be ready for use immediately. Use the command rcdhcpd check-syntax to perform a brief syntax check. If you encounter any unexpected problems with your configuration (the server aborts with an error or does not return done on start) ,you should be able to find out what has gone wrong by looking for information either in the main system log /var/log/messages or on console 10 (Ctrl+Alt+F10).

On a default openSUSE system, the DHCP daemon is started in a chroot environment for security reasons. The configuration files must be copied to the chroot environment so the daemon can find them. Normally, there is no need to worry about this because the command rcdhcpd start automatically copies the files.

Clients with Fixed IP Addresses

DHCP can also be used to assign a predefined, static address to a specific client. Addresses assigned explicitly always take priority over dynamic addresses from the pool. A static address never expires in the way a dynamic address would, for example, if there were not enough addresses available and the server needed to redistribute them among clients.

To identify a client configured with a static address, dhcpd uses the hardware address (which is a globally unique, fixed numerical code consisting of six octet pairs) for the identification of all network devices (for example, 00:30:6E:08:EC:80). If the respective lines, like the ones in Example 24.2, “Additions to the Configuration File”, are added to the configuration file of Example 24.1, “The Configuration File /etc/dhcpd.conf”, the DHCP daemon always assigns the same set of data to the corresponding client.

Example 24.2. Additions to the Configuration File

host jupiter {
hardware ethernet 00:30:6E:08:EC:80;
fixed-address 192.168.2.100;
}

The name of the respective client (host hostname, here jupiter) is entered in the first line and the MAC address in the second line. On Linux hosts, find the MAC address with the command ip link show followed by the network device (for example, eth0). The output should contain something like

link/ether 00:30:6E:08:EC:80

In the preceding example, a client with a network card having the MAC address 00:30:6E:08:EC:80 is assigned the IP address 192.168.2.100 and the hostname jupiter automatically. The type of hardware to enter is ethernet in nearly all cases, although token-ring, which is often found on IBM systems, is also supported.

The openSUSE Version

To improve security, the openSUSE version of the ISC's DHCP server comes with the non-root/chroot patch by Ari Edelkind applied. This enables dhcpd to run with the user ID nobody and run in a chroot environment (/var/lib/dhcp). To make this possible, the configuration file dhcpd.conf must be located in /var/lib/dhcp/etc. The init script automatically copies the file to this directory when starting.

Control the server's behavior regarding this feature by means of entries in the file /etc/sysconfig/dhcpd. To run dhcpd without the chroot environment, set the variable DHCPD_RUN_CHROOTED in /etc/sysconfig/dhcpd to “no”.

To enable dhcpd to resolve hostnames even from within the chroot environment, some other configuration files must be copied as well:

/etc/localtime

/etc/host.conf

/etc/hosts

/etc/resolv.conf

These files are copied to /var/lib/dhcp/etc/ when starting the init script. Take these copies into account for any changes that they require if they are dynamically modified by scripts like /etc/ppp/ip-up. However, there should be no need to worry about this if the configuration file only specifies IP addresses (instead of hostnames).

If your configuration includes additional files that should be copied into the chroot environment, set these under the variable DHCPD_CONF_INCLUDE_FILES in the file /etc/sysconfig/dhcpd. To ensure that the DHCP logging facility keeps working even after a restart of the syslog-ng daemon, there is an additional entry SYSLOGD_ADDITIONAL_SOCKET_DHCP in the file /etc/sysconfig/syslog.

For More Information

More information about DHCP is available at the Web site of the Internet Systems Consortium (http://www.isc.org/products/DHCP/). Information is also available in the dhcpd, dhcpd.conf, dhcpd.leases, and dhcp-options man pages.

Chapter 25. Time Synchronization with NTP

Abstract

The NTP (network time protocol) mechanism is a protocol for synchronizing the system time over the network. First, a machine can obtain the time from a server that is a reliable time source. Second, a machine can itself act as a time source for other computers in the network. The goal is twofold—maintaining the absolute time and synchronizing the system time of all machines within a network.

Maintaining an exact system time is important in many situations. The built-in hardware (BIOS) clock does often not meet the requirements of applications like databases. Manual correction of the system time would lead to severe problems because, for example, a backward leap can cause malfunction of critical applications. Within a network, it is usually necessary to synchronize the system time of all machines, but manual time adjustment is a bad approach. ntp provides a mechanism to solve these problems. It continuously adjusts the system time with the help of reliable time servers in the network. It further enables the management of local reference clocks, such as radio-controlled clocks.

Configuring an NTP Client with YaST

ntp is preset to use the local computer clock as a time reference. Using the (BIOS) clock, however, only serves as a fallback for the case that no time source of greater precision is available. YaST facilitates the configuration of an NTP client. For a system that is not running a firewall, use either the quick or advanced configuration. For a firewall-protected system, the advanced configuration can open the required ports in SuSEfirewall2.

Quick NTP Client Configuration

The quick NTP client configuration (Network Services+NTP Configuration) consists of two dialogs. Set the start mode of ntpd and the server to query in the first dialog. To start ntpd automatically when the system is booted, click Now and On Boot. Then specify the NTP Server Configuration. Either of 0.opensuse.pool.ntp.org, 1.opensuse.pool.ntp.org, 2.opensuse.pool.ntp.org, or 3.opensuse.pool.ntp.org is pre-selected. Click Use Random Servers from pool.ntp.org if you do not want to use the pre-selected time server. Alternatively, click Select to access a second dialog in which to select a suitable time server for your network.

In the pull-down Select list, determine whether to implement time synchronization using a time server from your local network (Local NTP Server) or an Internet-based time server that takes care of your time zone (Public NTP Server). For a local time server, click Lookup to start an SLP query for available time servers in your network. Select the most suitable time server from the list of search results and exit the dialog with OK. For a public time server, select your country (time zone) and a suitable server from the list under Public NTP Server then exit the dialog with OK. In the main dialog, test the availability of the selected server with Test and quit the dialog with Finish.

Advanced NTP Client Configuration

The advanced configuration of an NTP client can be accessed under Advanced Configuration from the main dialog of the NTP Configuration module, after selecting the start-up mode as described in the quick configuration.

Figure 25.1. Advanced NTP Configuration: General Settings

You can either configure the NTP client manually or automatically to get a list of the NTP servers available in your network via DHCP. If you choose Configure NTP Daemon via DHCP, the manual options explained below are not available.

The servers and other time sources for the client to query are listed in the lower part of the General Settings tab. Modify this list as needed with Add, Edit, and Delete. Display Log provides the possibility to view the log files of your client.

Click Add to add a new source of time information. In the following dialog, select the type of source with which the time synchronization should be made. The following options are available:

Server

Another dialog enables you to select an NTP server (as described in Section “Quick NTP Client Configuration”). Activate Use for Initial Synchronization to trigger the synchronization of the time information between the server and the client when the system is booted. Options allows you to specify additional options for ntpd.

Using Access Control Options, you can restrict the actions that the remote computer can perform with the daemon running on your computer. This field is enabled only after checking Restrict NTP Service to Configured Servers Only on the Security Settings tab. The options correspond to the restrict clauses in /etc/ntp.conf. For example, nomodify notrap noquery disallows the server to modify NTP settings of your computer and to use the trap facility (a remote event logging feature) of your NTP daemon. Using these restrictions is recommended for servers out of your control (for example, on the Internet).

Refer to /usr/share/doc/packages/ntp-doc (part of the ntp-doc package) for detailed information.

Peer

A peer is a machine to which a symmetric relationship is established: it acts both as a time server and as a client. To use a peer in the same network instead of a server, enter the address of the system. The rest of the dialog is identical to the Server dialog.

Radio Clock

To use a radio clock in your system for the time synchronization, enter the clock type, unit number, device name, and other options in this dialog. Click Driver Calibration to fine-tune the driver. Detailed information about the operation of a local radio clock is available in /usr/share/doc/packages/ntp-doc/refclock.html.

Outgoing Broadcast

Time information and queries can also be transmitted by broadcast in the network. In this dialog, enter the address to which such broadcasts should be sent. Do not activate broadcasting unless you have a reliable time source like a radio controlled clock.

Incoming Broadcast

If you want your client to receive its information via broadcast, enter the address from which the respective packets should be accepted in this fields.

Figure 25.2. Advanced NTP Configuration: Security Settings

In the Security Settings tab, determine whether ntpd should be started in a chroot jail. By default, Run NTP Daemon in Chroot Jail is activated. This increases the security in the event of an attack over ntpd, as it prevents the attacker from compromising the entire system.

Restrict NTP Service to Configured Servers Only increases the security of your system by disallowing remote computers to view and modify NTP settings of your computer and to use the trap facility for remote event logging. Once enabled, these restrictions apply to all remote computers, unless you override the access control options for individual computers in the list of time sources in the General Settings tab. For all other remote computers, only querying for local time is allowed.

Enable Open Port in Firewall if SuSEfirewall2 is active (which it is by default). If you leave the port closed, it is not possible to establish a connection to the time server.

Manually Configuring ntp in the Network

The easiest way to use a time server in the network is to set server parameters. For example, if a time server called ntp.example.com is reachable from the network, add its name to the file /etc/ntp.conf by adding the following line:

server ntp.example.com

To add more time servers, insert additional lines with the keyword server. After initializing ntpd with the command rcntp start, it takes about one hour until the time is stabilized and the drift file for correcting the local computer clock is created. With the drift file, the systematic error of the hardware clock can be computed as soon as the computer is powered on. The correction is used immediately, resulting in a higher stability of the system time.

There are two possible ways to use the NTP mechanism as a client: First, the client can query the time from a known server in regular intervals. With many clients, this approach can cause a high load on the server. Second, the client can wait for NTP broadcasts sent out by broadcast time servers in the network. This approach has the disadvantage that the quality of the server is unknown and a server sending out wrong information can cause severe problems.

If the time is obtained via broadcast, you do not need the server name. In this case, enter the line broadcastclient in the configuration file /etc/ntp.conf. To use one or more known time servers exclusively, enter their names in the line starting with servers.

Setting Up a Local Reference Clock

The software package ntp contains drivers for connecting local reference clocks. A list of supported clocks is available in the ntp-doc package in the file /usr/share/doc/packages/ntp-doc/refclock.html. Every driver is associated with a number. In ntp, the actual configuration takes place by means of pseudo IP addresses. The clocks are entered in the file /etc/ntp.conf as though they existed in the network. For this purpose, they are assigned special IP addresses in the form 127.127.t.u. Here, t stands for the type of the clock and determines which driver is used and u for the unit, which determines the interface used.

Normally, the individual drivers have special parameters that describe configuration details. The file /usr/share/doc/packages/ntp-doc/drivers/driverNN.html (where NN is the number of the driver) provides information about the particular type of clock. For example, the “type 8” clock (radio clock over serial interface) requires an additional mode that specifies the clock more precisely. The Conrad DCF77 receiver module, for example, has mode 5. To use this clock as a preferred reference, specify the keyword prefer. The complete server line for a Conrad DCF77 receiver module would be:

server 127.127.8.0 mode 5 prefer

Other clocks follow the same pattern. Following the installation of the ntp-doc package, the documentation for ntp is available in the directory /usr/share/doc/packages/ntp-doc. The file /usr/share/doc/packages/ntp-doc/refclock.html provides links to the driver pages describing the driver parameters.

Chapter 26. Sharing File Systems with NFS

Distributing and sharing file systems over a network is a common task in corporate environments. NFS is a proven system that also works together with the yellow pages protocol NIS. For a more secure protocol that works together with LDAP and may also be kerberized, check NFSv4.

NFS works with NIS to make a network transparent to the user. With NFS, it is possible to distribute arbitrary file systems over the network. With an appropriate setup, users always find themselves in the same environment regardless of the terminal they currently use.

Like NIS, NFS is a client/server system. However, a machine can be both—it can supply file systems over the network (export) and mount file systems from other hosts (import).

Need for DNS

In principle, all exports can be made using IP addresses only. To avoid time-outs, you should have a working DNS system. This is necessary at least for logging purposes, because the mountd daemon does reverse lookups.

Installing the Required Software

To configure your host as an NFS client, you do not need to install additional software. All packages needed to configure an NFS client are installed by default.

NFS server software is not part of the default installation. To install the NFS server software, start YaST and select Software+Software Management. Now choose Filter+Patterns and select Misc. Server or use the Search option and search for NFS Server. Confirm the installation of the packages to finish the installation process.

Importing File Systems with YaST

Users authorized to do so can mount NFS directories from an NFS server into their own file trees. This can be achieved using the YaST module NFS Client. Click on Add and enter the hostname of the NFS server, the directory to import, and the mount point at which to mount this directory locally. The changes will take effect after Finish is clicked in the first dialog.

In the NFS Settings tab, click Open Port in Firewall to open the firewall to allow access to the service from remote computers. The firewall status is displayed next to the check box. When using NFSv4, make sure that the checkbox Enable NFSv4 is enabled, and that the NFSv4 Domain Name contains the same value as used by the NFSv4 server. The default domain is localdomain.

Click Finish to save your changes. See Figure 26.1, “NFS Client Configuration with YaST”.

The configuration is written to /etc/fstab and the specified file systems are mounted. When you start the YaST configuration client at a later time, it also reads the existing configuration from this file.

Figure 26.1. NFS Client Configuration with YaST

Importing File Systems Manually

File systems can also be imported manually from an NFS server. The prerequisite for this is a running RPC port mapper, which can be started by entering rcrpcbind start as root. Once this prerequisite is met, remote exported file systems can be mounted in the file system just like local hard disks using the mount command in the following manner:

mount host:remote-path local-path

If user directories from the machine nfs.example.com, for example, should be imported, use the following command:

mount nfs.example.com:/home /home

Using the Automount Service

As well as the regular local device mounts, the autofs daemon can be used to mount remote file systems automatically, as well. To do this, add the following entry in the your /etc/auto.master file:

/nfsmounts /etc/auto.nfs

Now the /nfsmounts directory acts as a root for all the NFS mounts on the client if the auto.nfs file is completed appropriately. The name auto.nfs is chosen for sake of convenience—you can choose any name. In the selected file (create it if it does not exist), add entries for all the NFS mounts as in the following example:

localdata -fstype=nfs server1:/data
nfs4mount -fstype=nfs4 server2:/

Activate the settings with rcautofs start. For this example, /nfsmounts/localdata, the /data directory of server1, is then mounted with NFS and /nfsmounts/nfs4mount from server2 is mounted with NFSv4.

If the /etc/auto.master file is edited while the service autofs is running, the automounter must be restarted for the changes to take effect. Do this with rcautofs restart.

Manually Editing /etc/fstab

A typical NFSv3 mount entry in /etc/fstab looks like this:

nfs.example.com:/data /local/path nfs rw,noauto 0 0

NFSv4 mounts may also be added to the /etc/fstab file manually. For these mounts, use nfs4 instead of nfs in the third column and make sure that the remote file system is given as / after the nfs.example.com: in the first column. A sample line for an NFSv4 mount in /etc/fstab looks like this:

nfs.example.com:/ /local/pathv4 nfs4 rw,noauto 0 0

The noauto option prevents the file system from being mounted automatically at start up. If you want to mount the respective file system manually, it is possible to shorten the command for mounting and it is only needed to provide the mount point as in:

mount /local/path

Note, that if you do not enter the noauto option, the initialization scripts of the system will handle the mount of those file systems at start up.

Exporting File Systems with YaST

With YaST, turn a host in your network into an NFS server—a server that exports directories and files to all hosts granted access to it. This could be done to provide applications to all members of a group without installing them locally on each and every host. To install such a server, start YaST and select Network Services+NFS Server. A dialog like the one in Figure 26.2, “NFS Server Configuration Tool” opens.

Figure 26.2. NFS Server Configuration Tool

Then activate Start NFS Server and enter the NFSv4 Domain Name.

Click Enable GSS Security if you need secure access to the server. A prerequisite for this is to have Kerberos installed on your domain and to have both the server and the clients kerberized. Click Next.

In the upper text field, enter the directories to export. Below, enter the hosts that should have access to them. This dialog is shown in Figure 26.3, “Configuring an NFS Server with YaST”. The figure shows the scenario where NFSv4 is enabled in the previous dialog. Bindmount Targets is shown in the right pane. For more details, refer to the help shown on the left pane. In the lower half of the dialog, there are four options that can be set for each host: single host, netgroups, wildcards, and IP networks. For a more thorough explanation of these options, refer to the exports man page. Click Finish to complete the configuration.

Figure 26.3. Configuring an NFS Server with YaST

Automatic Firewall Configuration

If a firewall is active on your system (SuSEfirewall2), YaST adapts its configuration for the NFS server by enabling the nfs service when Open Ports in Firewall is selected.

Exporting for NFSv4 Clients

Activate Enable NFSv4 to support NFSv4 clients. Clients with NFSv3 can still access the server's exported directories if they are exported appropriately. This is explained in detail in Section “Coexisting v3 and v4 Exports”.

After activating NFSv4, enter an appropriate domain name. Make sure the name is the same as the one in the /etc/idmapd.conf file of any NFSv4 client that accesses this particular server. This parameter is for the idmapd service that is required for NFSv4 support (on both server and client). Leave it as localdomain (the default) if you do not have special requirements. For more information, see Section “For More Information”.

Click Next. The dialog that follows has two sections. The upper half consists of two columns named Directories and Bind Mount Targets. Directories is a directly editable column that lists the directories to export.

For a fixed set of clients, there are two types of directories that can be exported—directories that act as pseudo root file systems and those that are bound to some subdirectory of the pseudo file system. This pseudo file system acts as a base point under which all file systems exported for the same client set take their place. For a client or set of clients, only one directory on the server can be configured as pseudo root for export. For this client, export multiple directories by binding them to some existing subdirectory in the pseudo root.

Figure 26.4. Exporting Directories with NFSv4

In the lower half of the dialog, enter the client (wild card) and export options for a particular directory. After adding a directory in the upper half, another dialog for entering the client and option information pops up automatically. After that, to add a new client (client set), click Add Host.

In the small dialog that opens, enter the host wild card. There are four possible types of host wild cards that can be set for each host: a single host (name or IP address), netgroups, wild cards (such as * indicating all machines can access the server), and IP networks. Then, in Options, include fsid=0 in the comma-separated list of options to configure the directory as pseudo root. If this directory needs to be bound to another directory under an already configured pseudo root, make sure that a target bind path is given in the option list with bind=/target/path.

For example, suppose that the directory /exports is chosen as the pseudo root directory for all the clients that can access the server. Then add this in the upper half and make sure that the options entered for this directory include fsid=0. If there is another directory, /data, that also needs to be NFSv4 exported, add this directory to the upper half. While entering options for this, make sure that bind=/exports/data is in the list and that /exports/data is an already existing subdirectory of /exports. Any change in the option bind=/target/path, whether addition, deletion, or change in value, is reflected in Bindmount targets. This column is not a directly editable column, but instead summarizes directories and their nature. After the information is complete, click Finish to complete the configuration or Start to restart the service.

NFSv3 and NFSv2 Exports

Make sure that Enable NFSv4 is not checked in the initial dialog before clicking Next.

The next dialog has two parts. In the upper text field, enter the directories to export. Below, enter the hosts that should have access to them. There are four types of host wild cards that can be set for each host: a single host (name or IP address), netgroups, wild cards (such as * indicating all machines can access the server), and IP networks.

This dialog is shown in Figure 26.5, “Exporting Directories with NFSv2 and v3”. Find a more thorough explanation of these options in man exports. Click Finish to complete the configuration.

Figure 26.5. Exporting Directories with NFSv2 and v3

Coexisting v3 and v4 Exports

Both, NFSv3 and NFSv4 exports can coexist on a server. After enabling the support for NFSv4 in the initial configuration dialog, those exports for which fsid=0 and bind=/target/path are not included in the option list are considered v3 exports. Consider the example in Figure 26.3, “Configuring an NFS Server with YaST”. If you add another directory, such as /data2, using Add Directory then in the corresponding options list do not mention either fsid=0 or bind=/target/path, this export acts as a v3 export.

Important

Automatic Firewall Configuration

If SuSEfirewall2 is active on your system, YaST adapts its configuration for the NFS server by enabling the nfs service when Open Ports in Firewall is selected.

Exporting File Systems Manually

The configuration files for the NFS export service are /etc/exports and /etc/sysconfig/nfs. In addition to these files, /etc/idmapd.conf is needed for the NFSv4 server configuration. To start or restart the services, run the command rcnfsserver restart. This also starts the rpc.idmapd if NFSv4 is configured in /etc/sysconfig/nfs. The NFS server depends on a running RPC portmapper. Therefore, also start or restart the portmapper service with rcrpcbind restart.

Exporting File Systems with NFSv4

NFSv4 is the latest version of NFS protocol available on openSUSE. Configuring the directories for export with NFSv4 differs slightly from the previous NFS versions.

The /etc/exports File

This file contains a list of entries. Each entry indicates a directory that is shared and how it is shared. A typical entry in /etc/exports consists of:

/shared/directory host(option_list)

For example:

/export 192.168.1.2(rw,fsid=0,sync,crossmnt)
/export/data 192.168.1.2(rw,bind=/data,sync)

Here the IP address 192.168.1.2 is used to identify the allowed client. You can also use the name of the host, a wild card indicating a set of hosts (*.abc.com, *, etc.), or netgroups (@my-hosts).

The directory which specifies fsid=0 is special in that it is the root of the filesystem that is exported, sometime referred to as the pseudo root filesystem. This directory must also have the crossmnt for correct operation with NFSv4. All other directories exported via NFSv4 must be mounted below this point. If you want to export a directory that is not normally below this exported root, it needs to be bound into the exported tree. This can be done using the bind= syntax.

In the example above, /data is not below the /export, but we want to export it anyway, so we export /export/data, and specify that the /data directory should be bound to that name. The directory /export/data must exist and should normally be empty.

When clients mount from this server, that should just mount servername:/ rather than servername:/export. It is not necessary to also mount servername:/data and that will automatically appear beneath wherever servername:/ was mounted.

/etc/sysconfig/nfs

This file contains a few parameters that determine NFSv4 server daemon behavior. Importantly, the parameter NFSv4_SUPPORT must be set to yes. This parameter determines whether the NFS server supports NFSv4 exports and clients.

/etc/idmapd.conf

Every user on a Linux machine has a name and ID. idmapd does the name-to-ID mapping for NFSv4 requests to the server and replies to the client. This must be running on both server and client for NFSv4, because NFSv4 uses only names for its communication.

Make sure that there is a uniform way in which usernames and IDs (uid) are assigned to users across machines that might probably be sharing file systems using NFS. This can be achieved by using NIS, LDAP, or any uniform domain authentication mechanism in your domain.

For proper function, the parameter Domain must be set the same for both, client and server in this file. If you are not sure, leave the domain as localdomain in the server and client files. A sample configuration file looks like the following:

[General]

Verbosity = 0
Pipefs-Directory = /var/lib/nfs/rpc_pipefs
Domain = localdomain

[Mapping]

Nobody-User = nobody
Nobody-Group = nobody

Do not change these parameters unless you know exactly what you are doing. For further reference, read the man page of idmapd and idmapd.conf; man idmapd, man idmapd.conf.

Starting and Stopping Services

After changing /etc/exports or /etc/sysconfig/nfs, start or restart the nfs server service with rcnfsserver restart. After changing /etc/idmapd.conf, reload the configuration file with the command killall -HUP rpc.idmapd.

If this service needs to start at boot time, run the command chkconfig nfsserver on.

Exporting File Systems with NFSv2 and NFSv3

This is specific to NFSv3 and NFSv2 exports. Refer to Section “Exporting for NFSv4 Clients” for exporting with NFSv4.

Exporting file systems with NFS involves two configuration files: /etc/exports and /etc/sysconfig/nfs. A typical /etc/exports file entry is in the format:

/shared/directory host(list_of_options)

For example:

/export 192.168.1.2(rw,sync)

Here, the directory /export is shared with the host 192.168.1.2 with the option list rw,sync. This IP address can be replaced with a client name or set of clients using a wild card (such as *.abc.com) or even netgroups.

For a detailed explanation of all options and their meanings, refer to the man page of exports (man exports).

After changing /etc/exports or /etc/sysconfig/nfs, start or restart the NFS server using the command rcnfsserver restart.

NFS with Kerberos

To use Kerberos authentication for NFS, GSS security must be enabled. To do so, select Enable GSS Security in the initial YaST dialog. Note, that you must have a working Kerberos server to use this feature. YaST does not set up the server but only uses the provided functionality. If you want to use Kerberos authentication in addition to the YaST configuration, complete at least the following steps before running the NFS configuration:

Make sure that both the server and the client are in the same Kerberos domain. This means that they access the same KDC (Key Distribution Center) server and share their krb5.keytab file (the default location on any machine is /etc/krb5.keytab).

Start the gssd service on the client with rcgssd start.

Start the svcgssd service on the server with rcsvcgssd start.

For further information about configuring kerberized NFS, refer to the links in Section “For More Information”.

For More Information

As well as the man pages of exports, nfs, and mount, information about configuring an NFS server and client is available in /usr/share/doc/packages/nfsidmap/README. Online documentation can be found at the following Web documents:

Find the detailed technical documentation online at SourceForge.

For instructions for setting up kerberized NFS, refer to NFS Version 4 Open Source Reference Implementation.

If you have any questions on NFSv4, refer to the Linux NFSv4 Frequently Asked Questions FAQ.

Chapter 27. Samba

Abstract

Using Samba, a Unix machine can be configured as a file and print server for Mac OS X, Windows, and OS/2 machines. Samba has developed into a fully-fledged and rather complex product. Configure Samba with YaST, SWAT (a Web interface), or by editing the configuration file manually.

Terminology

The following are some terms used in Samba documentation and in the YaST module.

SMB protocol

Samba uses the SMB (server message block) protocol that is based on the NetBIOS services. Microsoft released the protocol so other software manufacturers could establish connections to a Microsoft domain network. With Samba, the SMB protocol works on top of the TCP/IP protocol, so the TCP/IP protocol must be installed on all clients.

CIFS protocol

CIFS (common Internet file system) protocol is another protocol supported by Samba. CIFS defines a standard remote file system access protocol for use over the network, enabling groups of users to work together and share documents across the network.

NetBIOS

NetBIOS is a software interface (API) designed for communication between machines providing a name service. It enables machines connected to the network to reserve names for themselves. After reservation, these machines can be addressed by name. There is no central process that checks names. Any machine on the network can reserve as many names as it wants as long as the names are not already in use. The NetBIOS interface can be implemented for different network architectures. An implementation that works relatively closely with network hardware is called NetBEUI, but this is often referred to as NetBIOS. Network protocols implemented with NetBIOS are IPX from Novell (NetBIOS via TCP/IP) and TCP/IP.

The NetBIOS names sent via TCP/IP have nothing in common with the names used in /etc/hosts or those defined by DNS. NetBIOS uses its own, completely independent naming convention. However, it is recommended to use names that correspond to DNS hostnames to make administration easier or use DNS natively. This is the default used by Samba.

Samba server

Samba server provides SMB/CIFS services and NetBIOS over IP naming services to clients. For Linux, there are three daemons for Samba server: smnd for SMB/CIFS services, nmbd for naming services, and winbind for authentication.

Samba client

The Samba client is a system that uses Samba services from a Samba server over the SMB protocol. All common operating systems, such as Mac OS X, Windows, and OS/2, support the SMB protocol. The TCP/IP protocol must be installed on all computers. Samba provides a client for the different UNIX flavors. For Linux, there is a kernel module for SMB that allows the integration of SMB resources on the Linux system level. You do not need to run any daemon for the Samba client.

Shares

SMB servers provide resources to the clients by means of shares. Shares are printers and directories with their subdirectories on the server. It is exported by means of a name and can be accessed by its name. The share name can be set to any name—it does not have to be the name of the export directory. A printer is also assigned a name. Clients can access the printer by its name.

DC

A domain controller (DC) is a server that handles accounts in domain. For data replication, additional domain controllers are available in one domain.

Installing a Samba Server

To install a Samba server, start YaST and select Software+Software Management. Choose Filter+Patterns and select File Server. Confirm the installation of the required packages to finish the installation process.

Starting and Stopping Samba

You can start or stop the Samba server automatically (during boot) or manually. Starting and stopping policy is a part of the YaST Samba server configuration described in Section “Configuring a Samba Server with YaST”.

To stop or start running Samba services with YaST, use System+System Services (Runlevel) and check winbind, smb, and nmb. From a command line, stop services required for Samba with rcsmb stop && rcnmb stop and start them with rcnmb start && rcsmb start; rcsmb cares about winbind if needed.

Configuring a Samba Server

A Samba server in openSUSE® can be configured in two different ways: with YaST or manually. Manual configuration offers a higher level of detail, but lacks the convenience of the YaST GUI.

Configuring a Samba Server with YaST

To configure a Samba server, start YaST and select Network Services+Samba Server.

Initial Samba Configuration

When starting the module for the first time, the Samba Installation dialog starts, prompting you to make just a few basic decisions concerning administration of the server then at the end of the configuration prompts for the password of Samba root. For later starts, the Samba Server Configuration dialog appears.

The Samba Installation dialog consists of two steps and optional detailed settings:

Workgroup or Domain Name

Select an existing name from Workgroup or Domain Name or enter a new one and click Next.

Samba Server Type

In the next step, specify whether your server should act as CD (PDC) and click Next.

Start-Up

Select whether you want to start Samba During Boot or Manually and click OK. Then in the final popup box, set the Samba root Password.

You can change all settings later in the Samba Configuration dialog with the Start-Up, Shares, and Identity tabs.

Advanced Samba Configuration

During the first start of the Samba server module the Samba Configuration dialog appears directly after the two initial steps described in Section “Initial Samba Configuration”. Use it to adjust your Samba server configuration.

After editing your configuration, click OK to save your settings.

Starting the Server

In the Start Up tab, configure the start of the Samba server. To start the service every time your system boots, select During Boot. To activate manual start, choose Manually. More information about starting a Samba server is provided in Section “Starting and Stopping Samba”.

In this tab, you can also open ports in your firewall. To do so, select Open Port in Firewall. If you have multiple network interfaces, select the network interface for Samba services by clicking Firewall Details, selecting the interfaces, and clicking OK.

Shares

In the Shares tab, determine the Samba shares to activate. There are some predefined shares, like homes and printers. Use Toggle Status to switch between Active and Inactive. Click Add to add new shares and Delete to delete the selected share.

Allow Users to Share Their Directories enables members of the group in Permitted Group to share directories they own with other users. For example, users for a local scope or DOMAIN\Users for a domain scope. The user also must make sure that the file system permissions allow access. With Maximum Number of Shares, limit the total amount of shares that may be created. To permit access to user shares without authentication, enable Allow Guest Access.

Identity

In the Identity tab, you can determine the domain with which the host is associated (Base Settings) and whether to use an alternative hostname in the network (NetBIOS Hostname). It is also possible to use Microsoft Windows Internet Name Service (WINS) for name resolution. In this case, activate Use WINS for Hostname Resolution and decide whether to Retrieve WINS server via DHCP. To set expert global settings or set user authentication, click Advanced Settings.

Web Administration with SWAT

An alternative tool for Samba server administration is SWAT (Samba Web Administration Tool). It provides a simple Web interface with which to configure the Samba server. To use SWAT, open http://localhost:901 in a Web browser and log in as user root. If you do not have a special Samba root account, use the system root account.

Activating SWAT

After Samba server installation, SWAT is not activated. To activate it, open Network Services+Network Services (xinetd) in YaST, enable the network services configuration, select swat from the table, and click Toggle Status (On or Off).

Configuring the Server Manually

If you intend to use Samba as a server, install samba. The main configuration file of Samba is /etc/samba/smb.conf. This file can be divided into two logical parts. The [global] section contains the central and global settings. The [share] sections contain the individual file and printer shares. By means of this approach, details regarding the shares can be set differently or globally in the [global] section, which enhances the structural transparency of the configuration file.

The global Section

The following parameters of the [global] section need some adjustment to match the requirements of your network setup so other machines can access your Samba server via SMB in a Windows environment.

workgroup = TUX-NET

This line assigns the Samba server to a workgroup. Replace TUX-NET with an appropriate workgroup of your networking environment. Your Samba server appears under its DNS name unless this name has been assigned to some other machine in the network. If the DNS name is not available, set the server name using netbiosname=MYNAME. For more details about this parameter, see the smb.conf man page.

os level = 2

This parameter triggers whether your Samba server tries to become LMB (local master browser) for its workgroup. Choose a very low value to spare the existing Windows network from any disturbances caused by a misconfigured Samba server. More information about this important topic can be found in the files BROWSING.txt and BROWSING-Config.txt under the textdocs subdirectory of the package documentation.

If no other SMB server is present in your network (such as a Windows 2000 server) and you want the Samba server to keep a list of all systems present in the local environment, set the os level to a higher value (for example, 65). Your Samba server is then chosen as LMB for your local network.

When changing this setting, consider carefully how this could affect an existing Windows network environment. First test the changes in an isolated network or at a noncritical time of day.

wins support and wins server

To integrate your Samba server into an existing Windows network with an active WINS server, enable the wins server option and set its value to the IP address of that WINS server.

If your Windows machines are connected to separate subnets and need to still be aware of each other, you need to set up a WINS server. To turn a Samba server into such a WINS server, set the option wins support = Yes. Make sure that only one Samba server of the network has this setting enabled. The options wins server and wins support must never be enabled at the same time in your smb.conf file.

Shares

The following examples illustrate how a CD-ROM drive and the user directories (homes) are made available to the SMB clients.

[cdrom]

To avoid having the CD-ROM drive accidentally made available, these lines are deactivated with comment marks (semicolons in this case). Remove the semicolons in the first column to share the CD-ROM drive with Samba.

Example 27.1. A CD-ROM Share (deactivated)

;[cdrom]
;       comment = Linux CD-ROM
;       path = /media/cdrom
;       locking = No

[cdrom] and comment

The entry [cdrom] is the name of the share that can be seen by all SMB clients on the network. An additional comment can be added to further describe the share.

path = /media/cdrom

path exports the directory /media/cdrom.

By means of a very restrictive default configuration, this kind of share is only made available to the users present on this system. If this share should be made available to everybody, add a line guest ok = yes to the configuration. This setting gives read permissions to anyone on the network. It is recommended to handle this parameter with great care. This applies even more to the use of this parameter in the [global] section.

[homes]

The [homes] share is of special importance here. If the user has a valid account and password for the Linux file server and his own home directory, he can be connected to it.

Example 27.2. homes Share

[homes]
	comment = Home Directories
	valid users = %S
	browseable = No
	read only = No
	create mask = 0640
	directory mask = 0750

[homes]

As long as there is no other share using the share name of the user connecting to the SMB server, a share is dynamically generated using the [homes] share directives. The resulting name of the share is the username.

valid users = %S

%S is replaced with the concrete name of the share as soon as a connection has been successfully established. For a [homes] share, this is always the username. As a consequence, access rights to a user's share are restricted exclusively to that user.

browseable = No

This setting makes the share invisible in the network environment.

read only = No

By default, Samba prohibits write access to any exported share by means of the read only = Yes parameter. To make a share writable, set the value read only = No, which is synonymous with writable = Yes.

create mask = 0640

Systems that are not based on MS Windows NT do not understand the concept of UNIX permissions, so they cannot assign permissions when creating a file. The parameter create mask defines the access permissions assigned to newly created files. This only applies to writable shares. In effect, this setting means the owner has read and write permissions and the members of the owner's primary group have read permissions. valid users = %S prevents read access even if the group has read permissions. For the group to have read or write access, deactivate the line valid users = %S.

Security Levels

To improve security, each share access can be protected with a password. SMB has four possible ways of checking the permissions:

Share Level Security (security = share)

A password is firmly assigned to a share. Everyone who knows this password has access to that share.

User Level Security (security = user)

This variation introduces the concept of the user to SMB. Each user must register with the server with his or her own password. After registration, the server can grant access to individual exported shares dependent on usernames.

Server Level Security (security = server)

To its clients, Samba pretends to be working in user level mode. However, it passes all password queries to another user level mode server, which takes care of authentication. This setting requires an additional parameter (password server).

ADS Level Security (security = ADS)

In this mode, Samba will act as a domain member in an Active Directory environment. To operate in this mode, the machine running Samba needs Kerberos installed and configured. You must join the machine using Samba to the ADS realm. This can be done using the YaST Windows Domain Membership module.

Domain Level Security (security = domain)

This mode will only work correctly if the machine has been joined into a Windows NT Domain. Samba will try to validate username and password by passing it to a Windows NT Primary or Backup Domain Controller. The same way as a Windows NT Server would do. It expects the encrypted passwords parameter to be set to yes.

The selection of share, user, server, or domain level security applies to the entire server. It is not possible to offer individual shares of a server configuration with share level security and others with user level security. However, you can run a separate Samba server for each configured IP address on a system.

More information about this subject can be found in the Samba HOWTO Collection. For multiple servers on one system, pay attention to the options interfaces and bind interfaces only.

Configuring Clients

Clients can only access the Samba server via TCP/IP. NetBEUI and NetBIOS via IPX cannot be used with Samba.

Configuring a Samba Client with YaST

Configure a Samba client to access resources (files or printers) on the Samba server. Enter the domain or workgroup in the dialog Network Services+Windows Domain Membership. If you activate Also Use SMB Information for Linux Authentication, the user authentication runs over the Samba server. After completing all settings, click Finish to finish the configuration.

Samba as Login Server

In networks where predominantly Windows clients are found, it is often preferable that users may only register with a valid account and password. In a Windows-based network, this task is handled by a primary domain controller (PDC). You can use a Windows NT server configured as PDC, but this task can also be done with the help of a Samba server. The entries that must be made in the [global] section of smb.conf are shown in Example 27.3, “Global Section in smb.conf”.

Example 27.3. Global Section in smb.conf

[global]
    workgroup = TUX-NET
    domain logons = Yes
    domain master = Yes

If encrypted passwords are used for verification purposes the Samba server must be able to handle these. The entry encrypt passwords = yes in the [global] section enables this (with Samba version 3, this is now the default). In addition, it is necessary to prepare user accounts and passwords in an encryption format that conforms with Windows. Do this with the command smbpasswd -a name. Create the domain account for the computers, required by the Windows domain concept, with the following commands:

useradd hostname\$
smbpasswd -a -m hostname

With the useradd command, a dollar sign is added. The command smbpasswd inserts this automatically when the parameter -m is used. The commented configuration example (/usr/share/doc/packages/samba/examples/smb.conf.SUSE) contains settings that automate this task.

add machine script = /usr/sbin/useradd -g nogroup -c "NT Machine Account" \
-s /bin/false %m\$

To make sure that Samba can execute this script correctly, choose a Samba user with the required administrator permissions. To do so, select one user and add it to the ntadmin group. After that, all users belonging to this Linux group can be assigned Domain Admin status with the command:

net groupmap add ntgroup="Domain Admins" unixgroup=ntadmin

More information about this topic is provided in Chapter 12 of the Samba 3 HOWTO, found in /usr/share/doc/packages/samba/Samba3-HOWTO.pdf.

For More Information

Detailed Samba information is available in the digital documentation. Enter apropos samba at the command line to display some manual pages or just browse the /usr/share/doc/packages/samba directory if Samba documentation is installed for more online documentation and examples. Find a commented example configuration (smb.conf.SUSE) in the examples subdirectory.

The Samba 3 HOWTO provided by the Samba team includes a section about troubleshooting. In addition to that, Part V of the document provides a step-by-step guide to checking your configuration. You can find Samba 3 HOWTO in /usr/share/doc/packages/samba/Samba3-HOWTO.pdf after installing the package samba-doc.

Also read the Samba page in the openSUSE wiki at http://en.openSUSE.org/Samba.

Chapter 28. The Apache HTTP Server

Abstract

With a share of more than 70%, the Apache HTTP Server (Apache) is the world's most widely-used Web server according to the Survey from http://www.netcraft.com/. Apache, developed by the Apache Software Foundation (http://www.apache.org/), is available for most operating systems. openSUSE® includes Apache version 2.2. In this chapter, learn how to install, configure and set up a Web server; how to use SSL, CGI, and additional modules; and how to troubleshoot Apache.

Quick Start

With the help of this section, quickly set up and start Apache. You must be root to install and configure Apache.

Requirements

Make sure that the following requirements are met before trying to set up the Apache Web server:

The machine's network is configured properly. For more information about this topic, refer to Chapter 21, Basic Networking.

The machine's exact system time is maintained by synchronizing with a time server. This is necessary because parts of the HTTP protocol depend on the correct time. See Chapter 25, Time Synchronization with NTP to learn more about this topic.

The latest security updates are installed. If in doubt, run a YaST Online Update.

The default Web server port (port 80) is opened in the firewall. For this, configure the SUSEFirewall2 to allow the service HTTP Server in the external zone. This can be done using YaST. “Configuring the Firewall with YaST” (Chapter “Masquerading and Firewalls”, ↑Security Guide) gives details.

Installation

Apache on openSUSE is not installed by default. To install it, start YaST and select Software+Software Management. Now choose Filter+Patterns and select Web and LAMP Server under Server Functions. Confirm the installation of the dependent packages to finish the installation process.

Apache is installed with a standard, predefined configuration that runs “out of the box”. The installation includes the multiprocessing module apache2-prefork as well the PHP5 module. Refer to Section “Installing, Activating, and Configuring Modules” for more information about modules.

Start

To start Apache and make sure that it is automatically started during boot, start YaST and select System+System Services (Runlevel). Search for apache2 and Enable the service. The Web server starts immediately. By saving your changes with Finish, the system is configured to automatically start Apache in runlevels 3 and 5 during boot. For more information about the runlevels in openSUSE and a description of the YaST runlevel editor, refer to Section “Configuring System Services (Runlevel) with YaST”.

To start Apache using the shell, run rcapache2 start. To make sure that Apache is automatically started during boot in runlevels 3 and 5, use chkconfig -a apache2.

If you do not receive error messages when starting Apache, the Web server should be running. Start a browser and open http://localhost/. You should see an Apache test page stating “It works!”. If you do not see this page, refer to Section “Troubleshooting”.

Now that the Web server is running, you can add your own documents, adjust the configuration according to your needs, or add functionality by installing modules.

Configuring Apache

Apache in openSUSE can be configured in two different ways: with YaST or manually. Manual configuration offers a higher level of detail, but lacks the convenience of the YaST GUI.

Configuration Changes

Changes to most configuration values for Apache only take effect after Apache is restarted or reloaded. This happens automatically when using YaST and finishing the configuration with Enabled checked for the HTTP Service. Manual restart is described in Section “Starting and Stopping Apache”. Most configuration changes only require a reload with rcapache2 reload.

Configuring Apache Manually

Configuring Apache manually involves editing the plain text configuration files as the user root.

Configuration Files

Apache configuration files can be found in two different locations:

/etc/sysconfig/apache2

/etc/apache2/

/etc/sysconfig/apache2

/etc/sysconfig/apache2 controls some global settings of Apache, like modules to load, additional configuration files to include, flags with which the server should be started, and flags that should be added to the command line. Every configuration option in this file is extensively documented and therefore not mentioned here. For a general-purpose Web server, the settings in /etc/sysconfig/apache2 should be sufficient for any configuration needs.

/etc/apache2/

/etc/apache2/ hosts all configuration files for Apache. In the following, the purpose of each file is explained. Each file includes several configuration options (also referred to as directives). Every configuration option in these files is extensively documented and therefore not mentioned here.

The Apache configuration files are organized as follows:

/etc/apache2/
 |
 |- charset.conv
 |- conf.d/
 |   |
 |   |- *.conf
 |
 |- default-server.conf
 |- errors.conf
 |- httpd.conf
 |- listen.conf
 |- magic
 |- mime.types
 |- mod_*.conf
 |- server-tuning.conf
 |- ssl.*
 |- ssl-global.conf
 |- sysconfig.d
 |   |
 |   |- global.conf
 |   |- include.conf
 |   |- loadmodule.conf . .
 |
 |- uid.conf
 |- vhosts.d
 |   |- *.conf

Apache Configuration Files in /etc/apache2/

charset.conv

Specifies which character sets to use for different languages. Do not edit.

conf.d/*.conf

Configuration files added by other modules. These configuration files can be included into your virtual host configuration where needed. See vhosts.d/vhost.template for examples. By doing so, you can provide different module sets for different virtual hosts.

default-server.conf

Global configuration for all virtual hosts with reasonable defaults. Instead of changing the values, overwrite them with a virtual host configuration.

errors.conf

Defines how Apache responds to errors. To customize these messages for all virtual hosts, edit this file. Otherwise overwrite these directives in your virtual host configurations.

httpd.conf

The main Apache server configuration file. Avoid changing this file. It primarily contains include statements and global settings. Overwrite global settings in the pertinent configuration files listed here. Change host-specific settings (such as document root) in your virtual host configuration.

listen.conf

Binds Apache to specific IP addresses and ports. Name-based virtual hosting (see Section “Name-Based Virtual Hosts” is also configured here.

magic

Data for the mime_magic module that helps Apache automatically determine the MIME type of an unknown file. Do not change.

mime.types

MIME types known by the system (this actually is a link to /etc/mime.types). Do not edit. If you need to add MIME types not listed here, add them to mod_mime-defaults.conf.

mod_*.conf

Configuration files for the modules that are installed by default. Refer to Section “Installing, Activating, and Configuring Modules” for details. Note that configuration files for optional modules reside in the directory conf.d.

server-tuning.conf

Contains configuration directives for the different MPMs (see Section “Multiprocessing Modules”) as well as general configuration options that control Apache's performance. Properly test your Web server when making changes here.

ssl-global.conf and ssl.*

Global SSL configuration and SSL certificate data. Refer to Section “Setting Up a Secure Web Server with SSL” for details.

sysconfig.d/*.conf

Configuration files automatically generated from /etc/sysconfig/apache2. Do not change any of these files—edit /etc/sysconfig/apache2 instead. Put no other configuration files in this directory.

uid.conf

Specifies under which user and group ID Apache runs. Do not change.

vhosts.d/*.conf

Your virtual host configuration should go here.The directory contains template files for virtual hosts with and without SSL. Every file in this directory ending in .conf is automatically included in the Apache configuration. Refer to Section “Virtual Host Configuration” for details.

Virtual Host Configuration

The term virtual host refers to Apache's ability to serve multiple URIs (universal resource identifiers) from the same physical machine. This means that several domains, such as www.example.com and www.example.net, are run by a single Web server on one physical machine.

It is common practice to use virtual hosts to save administrative effort (only a single Web server needs to be maintained) and hardware expenses (each domain does not require a dedicated server). Virtual hosts can be name based, IP based, or port based.

To list all existing virtual hosts, use the command httpd2 -S. This outputs a list showing the default server and all virtual hosts together with their IP addresses and listening ports. Furthermore, the list also contains an entry for each virtual host showing its location in the configuration files.

Virtual hosts can be configured via YaST (see Section “Virtual Hosts”) or by manually editing a configuration file. By default, Apache in openSUSE is prepared for one configuration file per virtual host in /etc/apache2/vhosts.d/. All files in this directory with the extension .conf are automatically included to the configuration. A basic template for a virtual host is provided in this directory (vhost.template or vhost-ssl.template for a virtual host with SSL support).

Always Create a Virtual Host Configuration

It is recommended to always create a virtual host configuration file, even if your Web server only hosts one domain. In doing so, you not only have the domain-specific configuration in one file, but you can always fall back to a working basic configuration by simply moving, deleting, or renaming the configuration file for the virtual host. For the same reason, you should also create separate configuration files for each virtual host.

When using name-based virtual hosts it is recommended to set up a default configuration that will be used when a domain name does not match a virtual host configuration. The default virtual host is the one whose configuration is loaded first. Since the order of the configuration files is determined by filename, start the filename of the default virtual host configuration with an “_”, e.g. _default_vhost.conf, to make sure it is loaded first.

The <VirtualHost></VirtualHost> block holds the information that applies to a particular domain. When Apache receives a client request for a defined virtual host, it uses the directives enclosed in this section. Almost all directives can be used in a virtual host context. See http://httpd.apache.org/docs/2.2/mod/quickreference.html for further information about Apache's configuration directives.

Name-Based Virtual Hosts

With name-based virtual hosts, more than one Web site is served per IP address. Apache uses the host field in the HTTP header sent by the client to connect the request to a matching ServerName entry of one of the virtual host declarations. If no matching ServerName is found, the first specified virtual host is used as a default.

The directive NameVirtualHost tells Apache on which IP address and, optionally, which port to listen for requests by clients containing the domain name in the HTTP header. This option is configured in the configuration file /etc/apache2/listen.conf.

The first argument can be a fully qualified domain name, but it is recommended to use the IP address. The second argument is the port and is optional. By default, port 80 is used and is configured via the Listen directive.

The wild card * can be used for both the IP address and the port number to receive requests on all interfaces. IPv6 addresses must be enclosed in square brackets.

Example 28.1. Variations of Name-Based VirtualHost Entries

# NameVirtualHost IP-address[:Port]
NameVirtualHost 192.168.3.100:80
NameVirtualHost 192.168.3.100
NameVirtualHost *:80
NameVirtualHost *
NameVirtualHost [2002:c0a8:364::]:80

The opening VirtualHost tag takes the IP address (or fully qualified domain name) previously declared with the NameVirtualHost as an argument in a name-based virtual host configuration. A port number previously declared with the NameVirtualHost directive is optional.

The wild card * is also allowed as a substitute for the IP address. This syntax is only valid in combination with the wild card usage in NameVirtualHost * . When using IPv6 addresses, the address must be included in square brackets.

Example 28.2. Name-Based VirtualHost Directives

<VirtualHost 192.168.3.100:80>
  ...
</VirtualHost>

<VirtualHost 192.168.3.100>
  ...
</VirtualHost>

<VirtualHost *:80>
  ...
</VirtualHost>

<VirtualHost *>
  ...
</VirtualHost>

<VirtualHost [2002:c0a8:364::]>
  ...
</VirtualHost>

IP-Based Virtual Hosts

This alternative virtual host configuration requires the setup of multiple IPs for a machine. One instance of Apache hosts several domains, each of which is assigned a different IP.

The physical server must have one IP address for each IP-based virtual host. If the machine does not have multiple network cards, virtual network interfaces (IP aliasing) can also be used.

The following example shows Apache running on a machine with the IP 192.168.3.100, hosting two domains on the additional IPs 192.168.3.101 and 192.168.3.102. A separate VirtualHost block is needed for every virtual server.

Example 28.3. IP-Based VirtualHost Directives

<VirtualHost 192.168.3.101>
  ...
</VirtualHost>

<VirtualHost 192.168.3.102>
  ...
</VirtualHost>

Here, VirtualHost directives are only specified for interfaces other than 192.168.3.100. When a Listen directive is also configured for 192.168.3.100, a separate IP-based virtual host must be created to answer HTTP requests to that interface—otherwise the directives found in the default server configuration (/etc/apache2/default-server.conf) are applied.

Basic Virtual Host Configuration

At least the following directives should be present in each virtual host configuration in order to set up a virtual host. See /etc/apache2/vhosts.d/vhost.template for more options.

ServerName

The fully qualified domain name under which the host should be addressed.

DocumentRoot

Path to the directory from which Apache should serve files for this host. For security reasons, access to the entire file system is forbidden by default, so you must explicitly unlock this directory within a Directory container.

ServerAdmin

E-mail address of the server administrator. This address is, for example, shown on error pages Apache creates.

ErrorLog

The error log file for this virtual host. Although it is not necessary to create separate error log files for each virtual host, it is common practice to do so, because it makes the debugging of errors much easier. /var/log/apache2/ is the default directory for Apache's log files.

CustomLog

The access log file for this virtual host. Although it is not necessary to create separate access log files for each virtual host, it is common practice to do so, because it allows the separate analysis of access statistics for each host. /var/log/apache2/ is the default directory for Apache's log files.

As mentioned above, access to the whole file system is forbidden by default for security reasons. Therefore, explicitly unlock the directories in which you have placed the files Apache should serve—for example the DocumentRoot:

<Directory "/srv/www/www.example.com/htdocs">
  Order allow,deny
  Allow from all
</Directory>

The complete configuration file looks like this:

Example 28.4. Basic VirtualHost Configuration

<VirtualHost 192.168.3.100>
  ServerName www.example.com;
  DocumentRoot /srv/www/www.example.com/htdocs
  ServerAdmin webmaster@example.com
  ErrorLog /var/log/apache2/www.example.com_log
  CustomLog /var/log/apache2/www.example.com-access_log common
  <Directory "/srv/www/www.example.com/htdocs">
    Order allow,deny
    Allow from all
  </Directory>
</VirtualHost>

Configuring Apache with YaST

To configure your Web server with YaST, start YaST and select Network Services+HTTP Server. When starting the module for the first time, the HTTP Server Wizard starts, prompting you to make a few basic decisions concerning administration of the server. After having finished the wizard, the dialog in Section “HTTP Server Configuration” starts each time you call the HTTP Server module.

HTTP Server Wizard

The HTTP Server Wizard consists of five steps. In the last step of the dialog, you are given the opportunity to enter the expert configuration mode to make even more specific settings.

Network Device Selection

Here, specify the network interfaces and ports Apache uses to listen for incoming requests. You can select any combination of existing network interfaces and their respective IP addresses. Ports from all three ranges (well-known ports, registered ports, and dynamic or private ports) that are not reserved by other services can be used. The default setting is to listen on all network interfaces (IP addresses) on port 80.

Check Open Firewall for Selected Ports to open the ports in the firewall that the Web server listens on. This is necessary to make the Web server available on the network, which can be a LAN, WAN, or the public Internet. Keeping the port closed is only useful in test situations where no external access to the Web server is necessary. If you have multiple network interfaces, click on Firewall Details... to specify on which interface(s) the port(s) should be opened.

Click Next to continue with configuration.

Modules

The Modules configuration option allows for the activation or deactivation of the script languages, the Web server should support. For the activation or deactivation of other modules, refer to Section “Server Modules”. Click Next to advance to the next dialog.

Default Host

This option pertains to the default Web server. As explained in Section “Virtual Host Configuration”, Apache can serve multiple virtual hosts from a single physical machine. The first declared virtual host in the configuration file is commonly referred to as the default host. Each virtual host inherits the default host's configuration.

To edit the host settings (also called directives), choose the appropriate entry in the table then click Edit. To add new directives, click Add. To delete a directive, select it and click Delete.

Figure 28.1. HTTP Server Wizard: Default Host

Here is list of the default settings of the server:

Document Root

Path to the directory from which Apache serves files for this host. /srv/www/htdocs is the default location.

Alias

With the help of Alias directives, URLs can be mapped to physical file system locations. This means that a certain path even outside the Document Root in the file system can be accessed via a URL aliasing that path.

The default openSUSE Alias /icons points to /usr/share/apache2/icons for the Apache icons displayed in the directory index view.

ScriptAlias

Similar to the Alias directive, the ScriptAlias directive maps a URL to a file system location. The difference is that ScriptAlias designates the target directory as a CGI location, meaning that CGI scripts should be executed in that location.

Directory

With Directory settings, you can enclose a group of configuration options that will only apply to the specified directory.

Access and display options for the directories /srv/www/htdocs, /usr/share/apache2/icons and /srv/www/cgi-bin are configured here. It should not be necessary to change the defaults.

Include

With include, additional configuration files can be specified. Two Include directives are already preconfigured: /etc/apache2/conf.d/ is the directory containing the configuration files that come with external modules. With this directive, all files in this directory ending in .conf are included. With the second directive, /etc/apache2/conf.d/apache2-manual.conf, the apache2-manual configuration file is included.

Server Name

This specifies the default URL used by clients to contact the Web server. Use a fully qualified domain name (FQDN) to reach the Web server at http://FQDN/ or its IP address. You cannot choose an arbitrary name here—the server must be “known” under this name.

Server Administrator E-Mail

E-mail address of the server administrator. This address is, for example, shown on error pages Apache creates.

After finishing with the Default Host step, click Next to continue with the configuration.

Virtual Hosts

In this step, the wizard displays a list of already configured virtual hosts (see Section “Virtual Host Configuration”). If you have not made manual changes prior to starting the YaST HTTP wizard, no virtual host is present.

To add a host, click Add to open a dialog in which to enter basic information about the host, such as Server Name, Server Contents Root (DocumentRoot), and the Administrator E-Mail. Server Resolution is used to determine how a host is identified (name based or IP based). Specify the name or IP address with Change Virtual Host ID

Clicking Next advances to the second part of the virtual host configuration dialog.

In part two of the virtual host configuration you can specify whether or not to enable CGI scripts and which directory to use for these scripts. It is also possible to enable SSL. If you do so, you must specify the path to the certificate as well. See Section “Configuring Apache with SSL” for details on SSL and certificates. With the Directory Index option, you can specify which file to display when the client requests a directory (by default, index.html). Add one or more filenames (space-separated) if you want to change this. With Enable Public HTML, the content of the users public directories (~user/public_html/) is made available on the server under http://www.example.com/~user.

Creating Virtual Hosts

It is not possible to add virtual hosts at will. If using name-based virtual hosts, each hostname must be resolved on the network. If using IP-based virtual hosts, you can assign only one host to each IP address available.

Summary

This is the final step of the wizard. Here, determine how and when the Apache server is started: when booting or manually. Also see a short summary of the configuration made so far. If you are satisfied with your settings, click Finish to complete configuration. If you want to change something, click Back until you have reached the desired dialog. Clicking HTTP Server Expert Configuration opens the dialog described in Section “HTTP Server Configuration”.

Figure 28.2. HTTP Server Wizard: Summary

HTTP Server Configuration

The HTTP Server Configuration dialog also lets you make even more adjustments to the configuration than the wizard (which only runs if you configure your Web server for the first time). It consists of four tabs described in the following. No configuration option you change here is effective immediately—you always must confirm your changes with Finish to make them effective. Clicking Abort leaves the configuration module and discards your changes.

Listen Ports and Addresses

In HTTP Service, select whether Apache should be running (Enabled) or stopped (Disabled). In Listen on Ports, Add, Edit, or Delete addresses and ports on which the server should be available. The default is to listen on all interfaces on port 80. You should always check Open Firewall on Selected Ports, because otherwise the Web server is not reachable from the outside. Keeping the port closed is only useful in test situations where no external access to the Web server is necessary. If you have multiple network interfaces, click on Firewall Details... to specify on which interface(s) the port(s) should be opened.

With Log Files, watch either the access log or the error log. This is useful if you want to test your configuration. The log file opens in a separate window from which you can also restart or reload the Web server (see Section “Starting and Stopping Apache” for details). These commands are effective immediately and their log messages are also displayed immediately.

Figure 28.3. HTTP Server Configuration: Listen Ports and Addresses

Server Modules

You can change the status (enabled or disabled) of Apache2 modules by clicking Toggle Status. Click Add Module to add a new module that is already installed but not yet listed. Learn more about modules in Section “Installing, Activating, and Configuring Modules”.

Figure 28.4. HTTP Server Configuration: Server Modules

Main Host or Hosts

These dialogs are identical to the ones already described. Refer to Section “Default Host” and Section “Virtual Hosts”.

Starting and Stopping Apache

If configured with YaST (see Section “Configuring Apache with YaST”), Apache is started at boot time in runlevels 3 and 5 and stopped in runlevels 0, 1, 2, and 6. You can change this behavior using YaST's runlevel editor or the command line tool chkconfig.

To start, stop, or manipulate Apache on a running system, use the init script /usr/sbin/rcapache2 (refer to Section “Init Scripts” for a general information about init scripts.). The rcapache2 command takes the following parameters:

status

Checks if Apache is started.

start

Starts Apache if it is not already running.

startssl

Starts Apache with SSL support if it is not already running. For more information about SSL support, refer to Section “Setting Up a Secure Web Server with SSL”.

stop

Stops Apache by terminating the parent process.

restart

Stops and then restarts Apache. Starts the Web server if it was not running before.

try-restart

Stops then restarts Apache only if it is already running.

reload or graceful

Stops the Web server by advising all forked Apache processes to first finish their requests before shutting down. As each process dies, it is replaced by a newly started one, resulting in complete “restart” of Apache.

Tip

rcapache2 reload is the preferred method of restarting Apache in production environments, for example, to activate a change in the configuration, because it allows all clients to be served without causing connection break-offs.

restart-graceful

Starts a second Web server that immediately serves all incoming requests. The previous instance of the Web server continues to handle all existing requests for a defined period of time configured with GracefulShutdownTimeout.

rcapache2 restart-graceful is either useful when upgrading to a new version or when having changed configuration options that require a restart. Using this option ensures a minimum server downtime.

GracefulShutdownTimeout needs to be set, otherwise restart-graceful will result in a regular restart. If set to zero, the server will wait indefinitely until all remaining requests have been fully served.

A graceful restart can fail if the original Apache instance is not able to clear all necessary resources. In this case, the command will result in a graceful stop.

stop-graceful

Stops the Web server after a defined period of time configured with GracefulShutdownTimeout in order to ensure that existing requests can be finished.

GracefulShutdownTimeout needs to be set, otherwise stop-graceful will result in a regular restart. If set to zero, the server will wait indefinitely until all remaining requests have been fully served.

configtest or extreme-configtest

Checks the syntax of the configuration files without affecting a running Web server. Because this check is forced every time the server is started, reloaded, or restarted, it is usually not necessary to run the test explicitly (if a configuration error is found, the Web server is not started, reloaded, or restarted). The extreme-configtest options starts the Web server as user nobody and actually loads the configuration, so more errors can be detected. Note that although the configuration is loaded, it is not possible to test the SSL setup because the SSL certificates cannot be read by nobody.

probe

Probes for the necessity of a reload (checks whether the configuration has changed) and suggests the required arguments for the rcapache2 command.

server-status and full-server-status

Dumps a short or full status screen, respectively. Requires either lynx or w3m installed as well as the module mod_status enabled. In addition to that, status must be added to APACHE_SERVER_FLAGS in the file /etc/sysconfig/apache2.

Additional Flags

If you specify additional flags to the rcapache2, these are passed through to the Web server.

Installing, Activating, and Configuring Modules

The Apache software is built in a modular fashion: all functionality except some core tasks is handled by modules. This has progressed so far that even HTTP is processed by a module (http_core).

Apache modules can be compiled into the Apache binary at build time or dynamically loaded at runtime. Refer to Section “Activation and Deactivation” for details of how to load modules dynamically.

Apache modules can be divided into four different categories:

Base Modules

Base modules are compiled into Apache by default. Apache in openSUSE has only mod_so (needed to load other modules) and http_core compiled in. All others are available as shared objects: rather than being included in the server binary itself, they can be included at runtime.

Extension Modules

In general, modules labeled as extensions are included in the Apache software package, but are usually not compiled into the server statically. In openSUSE, they are available as shared objects that can be loaded into Apache at runtime.

External Modules

Modules labeled external are not included in the official Apache distribution. openSUSE provides several of them readily available for use.

Multiprocessing Modules

MPMs are responsible for accepting and handling requests to the Web server, representing the core of the Web server software.

Module Installation

If you have followed the default way of installing Apache (described in Section “Installation”), it is installed with all base and extension modules, the multiprocessing module Prefork MPM, and the external modules mod_php5 and mod_python.

You can install additional external modules by starting YaST and choosing Software+Software Management. Now choose Filter+Search and search for apache. Among other packages, the results list contains all available external Apache modules.

Activation and Deactivation

Using YaST, you can activate or deactivate the script language modules (PHP5, Perl, and Python) with the module configuration described in Section “HTTP Server Wizard”. All other modules can be enabled or disabled as described in Section “Server Modules”.

If you prefer to activate or deactivate the modules manually, use the commands a2enmod mod_foo or a2dismod mod_foo, respectively. a2enmod -l outputs a list of all currently active modules.

Including Configuration Files for External Modules

If you have activated external modules manually, make sure to load their configuration files in all virtual host configurations. Configuration files for external modules are located under /etc/apache2/conf.d/ and are not loaded by default. If you need the same modules on each virtual host, you can include *.conf from this directory. Otherwise include individual files. See /etc/apache2/vhost.d/vhost.template for examples.

Base and Extension Modules

All base and extension modules are described in detail in the Apache documentation. Only a brief description of the most important modules is available here. Refer to http://httpd.apache.org/docs/2.2/mod/ to learn details about each module.

mod_actions

Provides methods to execute a script whenever a certain MIME type (such as application/pdf), a file with a specific extension (like .rpm), or a certain request method (such as GET) is requested. This module is enabled by default.

mod_alias

Provides Alias and Redirect directives with which you can map a URl to a specific directory (Alias) or redirect a requested URL to another location. This module is enabled by default.

mod_auth*

The authentication modules provide different authentication methods: basic authentication with mod_auth_basic or digest authentication with mod_auth_digest. Digest authentication in Apache 2.2 is considered experimental.

mod_auth_basic and mod_auth_digest must be combined with an authentication provider module, mod_authn_* (for example, mod_authn_file for text file–based authentication) and with an authorization module mod_authz_* (for example, mod_authz_user for user authorization).

More information about this topic is available in the “Authentication HOWTO” at http://httpd.apache.org/docs/2.2/howto/auth.html

mod_autoindex

Autoindex generates directory listings when no index file (for example, index.html) is present. The look and feel of these indexes is configurable. This module is enabled by default. However, directory listings are disabled by default via the Options directive—overwrite this setting in your virtual host configuration. The default configuration file for this module is located at /etc/apache2/mod_autoindex-defaults.conf.

mod_cgi

mod_cgi is needed to execute CGI scripts. This module is enabled by default.

mod_deflate

Using this module, Apache can be configured to compress given file types on the fly before delivering them.

mod_dir

mod_dir provides the DirectoryIndex directive with which you can configure which files are automatically delivered when a directory is requested (index.html by default). It also provides an automatic redirect to the correct URl when a directory request does not contain a trailing slash. This module is enabled by default.

mod_env

Controls the environment that is passed to CGI scripts or SSI pages. Environment variables can be set or unset or passed from the shell that invoked the httpd process. This module is enabled by default.

mod_expires

With mod_expires, you can control how often proxy and browser caches refresh your documents by sending an Expires header. This module is enabled by default.

mod_include

mod_include lets you use Server Side Includes (SSI), which provide a basic functionality to generate HTML pages dynamically. This module is enabled by default.

mod_info

Provides a comprehensive overview of the server configuration under http://localhost/server-info/. For security reasons, you should always limit access to this URL. By default only localhost is allowed to access this URL. mod_info is configured at /etc/apache2/mod_info.conf

mod_log_config

With this module, you can configure the look of the Apache log files. This module is enabled by default.

mod_mime

The mime module makes certain that a file is delivered with the correct MIME header based on the filename's extension (for example text/html for HTML documents). This module is enabled by default.

mod_negotiation

Necessary for content negotiation. See http://httpd.apache.org/docs/2.2/content-negotiation.html for more information. This module is enabled by default.

mod_rewrite

Provides the functionality of mod_alias, but offers more features and flexibility. With mod_rewrite, you can redirect URLs based on multiple rules, request headers, and more.

mod_setenvif

Sets environment variables based on details of the client's request, such as the browser string the client sends, or the client's IP address. This module is enabled by default.

mod_speling

mod_speling attempts to automatically correct typographical errors in URLs, such as capitalization errors.

mod_ssl

Enables encrypted connections between Web server and clients. See Section “Setting Up a Secure Web Server with SSL” for details. This module is enabled by default.

mod_status

Provides information on server activity and performance under http://localhost/server-status/. For security reasons, you should always limit access to this URL. By default, only localhost is allowed to access this URl. mod_status is configured at /etc/apache2/mod_status.conf

mod_suexec

mod_suexec lets you run CGI scripts under a different user and group. This module is enabled by default.

mod_userdir

Enables user-specific directories available under ~user/. The UserDir directive must be specified in the configuration. This module is enabled by default.

Multiprocessing Modules

openSUSE provides two different multiprocessing modules (MPMs) for use with Apache.

Prefork MPM

The prefork MPM implements a nonthreaded, preforking Web server. It makes the Web server behave similarly to Apache version 1.x in that it isolates each request and handles it by forking a separate child process. Thus problematic requests cannot affect others, avoiding a lockup of the Web server.

While providing stability with this process-based approach, the prefork MPM consumes more system resources than its counterpart, the worker MPM. The prefork MPM is considered the default MPM for Unix-based operating systems.

MPMs in This Document

This document assumes Apache is used with the prefork MPM.

Worker MPM

The worker MPM provides a multithreaded Web server. A thread is a “lighter” form of a process. The advantage of a thread over a process is its lower resource consumption. Instead of only forking child processes, the worker MPM serves requests by using threads with server processes. The preforked child processes are multithreaded. This approach makes Apache perform better by consuming fewer system resources than the prefork MPM.

One major disadvantage is the stability of the worker MPM: if a thread becomes corrupt, all threads of a process can be affected. In the worst case, this may result in a server crash. Especially when using the Common Gateway Interface (CGI) with Apache under heavy load, internal server errors might occur due to threads being unable to communicate with system resources. Another argument against using the worker MPM with Apache is that not all available Apache modules are thread-safe and thus cannot be used in conjunction with the worker MPM.

Using PHP Modules with MPMs

Not all available PHP modules are thread-safe. Using the worker MPM with mod_php is strongly discouraged.

External Modules

Find a list of all external modules shipped with openSUSE here. Find the module's documentation in the listed directory.

mod-apparmor

Adds support to Apache to provide Novell AppArmor confinement to individual CGI scripts handled by modules like mod_php5 and mod_perl.

Package Name: apache2-mod_apparmor

More Information: “Confining Privileges with Novell AppArmor” (↑Security Guide)

mod_mono

Using mod_mono allows you to run ASP.NET pages in your server.

Package Name: apache2-mod_mono

Configuration File: /etc/apache2/conf.d/mod_mono.conf

mod_perl

mod_perl enables you to run Perl scripts in an embedded interpreter. The persistent interpreter embedded in the server avoids the overhead of starting an external interpreter and the penalty of Perl start-up time.

Package Name: apache2-mod_perl

Configuration File: /etc/apache2/conf.d/mod_perl.conf

More Information: /usr/share/doc/packages/apache2-mod_perl

mod_php5

PHP is a server-side, cross-platform HTML embedded scripting language.

Package Name: apache2-mod_php5

Configuration File: /etc/apache2/conf.d/php5.conf

More Information: /usr/share/doc/packages/apache2-mod_php5

mod_python

mod_python allows embedding Python within the Apache HTTP server for a considerable boost in performance and added flexibility in designing Web-based applications.

Package Name: apache2-mod_python

More Information: /usr/share/doc/packages/apache2-mod_python

mod_tidy

mod_tidy validates each outgoing HTML page by means of the TidyLib. In case of a validation error, a page with an error list is delivered. Otherwise the original HTML page is delivered.

Package Name: apache2-mod_tidy

Configuration File: /etc/apache2/mod_tidy.conf

More Information: /usr/share/doc/packages/apache2-mod_tidy

Compilation

Apache can be extended by advanced users by writing custom modules. To develop modules for Apache or compile third-party modules, the package apache2-devel is required along with the corresponding development tools. apache2-devel also contains the apxs2 tools, which are necessary for compiling additional modules for Apache.

apxs2 enables the compilation and installation of modules from source code (including the required changes to the configuration files), which creates dynamic shared objects (DSOs) that can be loaded into Apache at runtime.

The apxs2 binaries are located under /usr/sbin:

/usr/sbin/apxs2—suitable for building an extension module that works with any MPM. The installation location is /usr/lib/apache2.

/usr/sbin/apxs2-prefork—suitable for prefork MPM modules. The installation location is /usr/lib/apache2-prefork.

/usr/sbin/apxs2-worker—suitable for worker MPM modules. The installation location is /usr/lib/apache2-worker.

Install and activate a module from source code with the commands cd /path/to/module/source; apxs2 -cia mod_foo.c (-c compiles the module, -i installs it, and -a activates it). Other options of apxs2 are described in the apxs2(1) man page.

Getting CGI Scripts to Work

Apache's Common Gateway Interface (CGI) lets you create dynamic content with programs or scripts usually referred to as CGI scripts. CGI scripts can be written in any programming language. Usually, script languages such as Perl or PHP are used.

To enable Apache to deliver content created by CGI scripts, mod_cgi needs to be activated. mod_alias is also needed. Both modules are enabled by default. Refer to Section “Activation and Deactivation” for details on activating modules.

CGI Security

Allowing the server to execute CGI scripts is a potential security hole. Refer to Section “Avoiding Security Problems” for additional information.

Apache Configuration

In openSUSE, the execution of CGI scripts is only allowed in the directory /srv/www/cgi-bin/. This location is already configured to execute CGI scripts. If you have created a virtual host configuration (see Section “Virtual Host Configuration”) and want to place your scripts in a host-specific directory, you must unlock and configure this directory.

Example 28.5. VirtualHost CGI Configuration

ScriptAlias /cgi-bin/ "/srv/www/www.example.com/cgi-bin/"

<Directory "/srv/www/www.example.com/cgi-bin/">
 Options +ExecCGI
 AddHandler cgi-script .cgi .pl
 Order allow,deny
 Allow from all
</Directory>

Tells Apache to handle all files within this directory as CGI scripts.

Enables CGI script execution

Tells the server to treat files with the extensions .pl and .cgi as CGI scripts. Adjust according to your needs.

The Order and Allow directives control the default access state and the order in which Allow and Deny directives are evaluated. In this case “deny” statements are evaluated before “allow” statements and universal access is enabled.

Running an Example Script

CGI programming differs from "regular" programming in that the CGI programs and scripts must be preceded by a MIME-Type header such as Content-type: text/html. This header is sent to the client, so it understands what kind of content it receives. Secondly, the script's output must be something the client, usually a Web browser, understands—HTML in most cases or plain text or images, for example.

A simple test script available under /usr/share/doc/packages/apache2/test-cgi is part of the Apache package. It outputs the content of some environment variables as plain text. Copy this script to either /srv/www/cgi-bin/ or the script directory of your virtual host (/srv/www/www.example.com/cgi-bin/) and name it test.cgi.

Files accessible by the Web server should be owned by to the user root (see Section “Avoiding Security Problems” for additional information). Because the Web server runs with a different user, the CGI scripts must be world-executable and world-readable. Change into the CGI directory and use the command chmod 755 test.cgi to apply the proper permissions.

Now call http://localhost/cgi-bin/test.cgi or http://www.example.com/cgi-bin/test.cgi. You should see the “CGI/1.0 test script report”.

Troubleshooting

If you do not see the output of the test program but an error message instead, check the following:

CGI Troubleshooting

Have you reloaded the server after having changed the configuration? Check with rcapache2 probe.

If you have configured your custom CGI directory, is it configured properly? If in doubt, try the script within the default CGI directory /srv/www/cgi-bin/ and call it with http://localhost/cgi-bin/test.cgi.

Are the file permissions correct? Change into the CGI directory and execute the ls -l test.cgi. Its output should start with

-rwxr-xr-x  1 root root

Make sure that the script does not contain programming errors. If you have not changed test.cgi, this should not be the case, but if you are using your own programs, always make sure that they do not contain programming errors.

Setting Up a Secure Web Server with SSL

Whenever sensitive data, such as credit card information, is transferred between Web server and client, it is desirable to have a secure, encrypted connection with authentication. mod_ssl provides strong encryption using the secure sockets layer (SSL) and transport layer security (TLS) protocols for HTTP communication between a client and the Web server. Using SSL/TSL, a private connection between Web server and client is established. Data integrity is ensured and client and server are able to authenticate each other.

For this purpose, the server sends an SSL certificate that holds information proving the server's valid identity before any request to a URL is answered. In turn, this guarantees that the server is the uniquely correct end point for the communication. Additionally, the certificate generates an encrypted connection between client and server that can transport information without the risk of exposing sensitive, plain-text content.

mod_ssl does not implement the SSL/TSL protocols itself, but acts as an interface between Apache and an SSL library. In openSUSE, the OpenSSL library is used. OpenSSL is automatically installed with Apache.

The most visible effect of using mod_ssl with Apache is that URLs are prefixed with https:// instead of http://.

Example Certificate

An example certificate for a hypothetical company “Snake Oil” is available when installing the package apache2-example-certificates.

Creating an SSL Certificate

In order to use SSL/TSL with the Web server, you need to create an SSL certificate. This certificate is needed for the authorization between Web server and client, so that each party can clearly identify the other party. To ensure the integrity of the certificate, it must be signed by a party every user trusts.

There are three types of certificates you can create: a “dummy” certificate for testing purposes only, a self-signed certificate for a defined circle of users that trust you, and a certificate signed by an independent, publicly-known certificate authority (CA).

Creating a certificate is basically a two step process. First, a private key for the certificate authority is generated then the server certificate is signed with this key.

For More Information

To learn more about concepts and definitions of SSL/TSL, refer to http://httpd.apache.org/docs/2.2/ssl/ssl_intro.html.

Creating a “Dummy” Certificate

Generating a dummy certificate is simple. Just call the script /usr/bin/gensslcert. It creates or overwrites the files listed below. Make use of gensslcert's optional switches to fine-tune the certificate. Call /usr/bin/gensslcert -h for more information.

/etc/apache2/ssl.crt/ca.crt

/etc/apache2/ssl.crt/server.crt

/etc/apache2/ssl.key/server.key

/etc/apache2/ssl.csr/server.csr

/root/.mkcert.cfg

A copy of ca.crt is also placed at /srv/www/htdocs/CA.crt for download.

Important

A dummy certificate should never be used on a production system. Only use it for testing purposes.

Creating a Self-Signed Certificate

If you are setting up a secure Web server for an Intranet or for a defined circle of users, it might be sufficient if you sign a certificate with your own certificate authority (CA).

Creating a self-signed certificate is an interactive nine-step process. Change into the directory /usr/share/doc/packages/apache2 and run the following command: ./mkcert.sh make --no-print-directory /usr/bin/openssl /usr/sbin/ custom. Do not attempt to run this command from outside this directory. The program provides a series of prompts, some of which require user input.

Procedure 28.1. Creating a Self-Signed Certificate with mkcert.sh

Decide the signature algorithm used for certificates

Choose RSA (R, the default), because some older browsers have problems with DSA.

Generating RSA private key for CA (1024 bit)

No interaction needed.

Generating X.509 certificate signing request for CA

Create the CA's distinguished name here. This requires you to answer a few questions, such as country name or organization name. Enter valid data, because everything you enter here later shows up in the certificate. You do not need to answer every question. If one does not apply to you or you want to leave it blank, use “.”. Common name is the name of the CA itself—choose a significant name, such as My company CA.

Common Name of the CA

The common name of the CA must be different from the server's common name, so do not choose the fully qualified hostname in this step.

Generating X.509 certificate for CA signed by itself

Choose certificate version 3 (the default).

Generating RSA private key for SERVER (1024 bit)

No interaction needed.

Generating X.509 certificate signing request for SERVER

Create the distinguished name for the server key here. Questions are almost identical to the ones already answered for the CA's distinguished name. The data entered here applies to the Web server and does not necessarily need to be identical to the CA's data (for example, if the server is located elsewhere).

Selecting a Common Name

The common name you enter here must be the fully qualified hostname of your secure server (for example, www.example.com). Otherwise the browser issues a warning that the certificate does not match the server when accessing the Web server.

Generating X.509 certificate signed by own CA

Choose certificate version 3 (the default).

Encrypting RSA private key of CA with a pass phrase for security

It is strongly recommended to encrypt the private key of the CA with a password, so choose Y and enter a password.

Encrypting RSA private key of SERVER with a pass phrase for security

Encrypting the server key with a password requires you to enter this password every time you start the Web server. This makes it difficult to automatically start the server on boot or to restart the Web server. Therefore, it is common sense to say N to this question. Keep in mind that your key is unprotected when not encrypted with a password and make sure that only authorized persons have access to the key.

Encrypting the Server Key

If you choose to encrypt the server key with a password, increase the value for APACHE_TIMEOUT in /etc/sysconfig/apache2. Otherwise you do not have enough time to enter the passphrase before the attempt to start the server is stopped unsuccessfully.

The script's result page presents a list of certificates and keys it has generated. Contrary to what the script outputs, the files have not been generated in the local directory conf, but to the correct locations under /etc/apache2/.

The last step is to copy the CA certificate file from /etc/apache2/ssl.crt/ca.crt to a location where your users can access it in order to incorporate it into the list of known and trusted CAs in their Web browsers. Otherwise a browser complains that the certificate was issued by an unknown authority. The certificate is valid for one year.

Self-Signed Certificates

Only use a self-signed certificate on a Web server that is accessed by people who know and trust you as a certificate authority. It is not recommended to use such a certificate on a public shop, for example.

Getting an Officially Signed Certificate

There are a number of official certificate authorities that sign your certificates. The certificate is signed by a trustworthy third party, so can be fully trusted. Publicly operating secure Web servers usually have got an officially signed certificate.

The best-known official CAs are Thawte (http://www.thawte.com/) or Verisign (http://www.verisign.com). These and other CAs are already compiled into all browsers, so certificates signed by these certificate authorities are automatically accepted by the browser.

When requesting an officially signed certificate, you do not send a certificate to the CA. Instead, issue a Certificate Signing Request (CSR). To create a CSR, call the script /usr/share/ssl/misc/CA.sh -newreq.

First the script asks for a password with which the CSR should be encrypted. Then you are asked to enter a distinguished name. This requires you to answer a few questions, such as country name or organization name. Enter valid data—everything you enter here later shows up in the certificate and is checked. You do not need to answer every question. If one does not apply to you or you want to leave it blank, use “.”. Common name is the name of the CA itself—choose a significant name, such as My company CA. Last, a challenge password and an alternative company name must be entered.

Find the CSR in the directory from which you called the script. The file is named newreq.pem.

Configuring Apache with SSL

The default port for SSL and TLS requests on the Web server side is 443. There is no conflict between a “regular” Apache listening on port 80 and an SSL/TLS-enabled Apache listening on port 443. In fact, HTTP and HTTPS can be run with the same Apache instance. Usually separate virtual hosts are used to dispatch requests to port 80 and port 443 to separate virtual servers.

Firewall Configuration

Do not forget to open the firewall for SSL-enabled Apache on port 443. This can be done with YaST as described in “Configuring the Firewall with YaST” (Chapter “Masquerading and Firewalls”, ↑Security Guide).

The SSL module is enabled by default in the global server configuration. In case it has been disabled on your host, activate it with the following command: a2enmod ssl. To finally enable SSL, the server needs to be started with the flag “SSL”. To do so, call a2enflag SSL. If you have chosen to encrypt your server certificate with a password, you should also increase the value for APACHE_TIMEOUT in /etc/sysconfig/apache2, so you have enough time to enter the passphrase when Apache starts. Restart the server to make these changes active. A reload is not sufficient.

The virtual host configuration directory contains a template /etc/apache2/vhosts.d/vhost-ssl.template with SSL-specific directives that are extensively documented. Refer to Section “Virtual Host Configuration” for the general virtual host configuration.

To get started, copy the template to /etc/apache2/vhosts.d/mySSL-host.conf and edit it. Adjusting the values for the following directives should be sufficient:

DocumentRoot

ServerName

ServerAdmin

ErrorLog

TransferLog

Name-Based Virtual Hosts and SSL

It is not possible to run multiple SSL-enabled virtual hosts on a server with only one IP address. Users connecting to such a setup receive a warning message stating that the certificate does not match the server name every time they visit the URL. A separate IP address or port is necessary for every SSL-enabled domain to achieve communication based on a valid SSL certificate.

Avoiding Security Problems

A Web server exposed to the public Internet requires an ongoing administrative effort. It is inevitable that security issues appear, both related to the software and to accidental misconfiguration. Here are some tips for how to deal with them.

Up-to-Date Software

If there are vulnerabilities found in the Apache software, a security advisory will be issued by SUSE. It contains instructions for fixing the vulnerabilities, which in turn should be applied as soon as possible. The SUSE security announcements are available from the following locations:

Web Page.  http://www.novell.com/linux/security/securitysupport.html

Mailing List.  http://en.opensuse.org/Communicate#Mailinglists

RSS Feed.  http://www.novell.com/linux/security/suse_security.xml

DocumentRoot Permissions

By default in openSUSE, the DocumentRoot directory /srv/www/htdocs and the CGI directory /srv/www/cgi-bin belong to the user and group root. You should not change these permissions. If the directories were writable for all, any user could place files into them. These files might then be executed by Apache with the permissions of wwwrun, which may give the user unintended access to file system resources. Use subdirectories of /srv/www to place the DocumentRoot and CGI directories for your virtual hosts and make sure that directories and files belong to user and group root.

File System Access

By default, access to the whole file system is denied in /etc/apache2/httpd.conf. You should never overwrite these directives, but specifically enable access to all directories Apache should be able to read (see Section “Basic Virtual Host Configuration” for details). In doing so, ensure that no critical files, such as password or system configuration files, can be read from the outside.

CGI Scripts

Interactive scripts in Perl, PHP, SSI, or any other programming language can essentially run arbitrary commands and therefore present a general security issue. Scripts that will be executed from the server should only be installed from sources the server administrator trusts—allowing users to run their own scripts is generally not a good idea. It is also recommended to do security audits for all scripts.

To make the administration of scripts as easy as possible, it is common practice to limit the execution of CGI scripts to specific directories instead of globally allowing them. The directives ScriptAlias and Option ExecCGI are used for configuration. The openSUSE default configuration does not allow execution of CGI scripts from everywhere.

All CGI scripts run as the same user, so different scripts can potentially conflict with each other. The module suEXEC lets you run CGI scripts under a different user and group.

User Directories

When enabling user directories (with mod_userdir or mod_rewrite) you should strongly consider not allowing .htaccess files, which would allow users to overwrite security settings. At least you should limit the user's engagement by using the directive AllowOverRide. In openSUSE, .htaccess files are enabled by default, but the user is not allowed to overwrite any Option directives when using mod_userdir (see the /etc/apache2/mod_userdir.conf configuration file).

Troubleshooting

If Apache does not start, the Web page is not accessible, or users cannot connect to the Web server, it is important to find the cause of the problem. Here are some typical places to look for error explanations and important things to check.

First, rcapache2 (described in Section “Starting and Stopping Apache”) is verbose about errors, so can be quite helpful if it is actually used for operating Apache. Sometimes it is tempting to use the binary /usr/sbin/httpd2 for starting or stopping the Web server. Avoid doing this and use the rcapache2 script instead. rcapache2 even provides tips and hints for solving configuration errors.

Second, the importance of log files cannot be overemphasized. In case of both fatal and nonfatal errors, the Apache log files, mainly the error log file, are the places to look for causes. Additionally, you can control the verbosity of the logged messages with the LogLevel directive if more detail is needed in the log files. By default, the error log file is located at /var/log/apache2/error_log.

A Simple Test

Watch the Apache log messages with the command tail -F /var/log/apache2/my_error_log. Then run rcapache2 restart. Now, try to connect with a browser and check the output.

A common mistake is to not open the ports for Apache in the firewall configuration of the server. If you configure Apache with YaST, there is a separate option available to take care of this specific issue (see Section “Configuring Apache with YaST”). If you are configuring Apache manually, open firewall ports for HTTP and HTTPS via YaST's firewall module.

If the error cannot be tracked down with the help of any these, check the online Apache bug database at http://httpd.apache.org/bug_report.html. Additionally, the Apache user community can be reached via a mailing list available at http://httpd.apache.org/userslist.html. A recommended newsgroup is comp.infosystems.www.servers.unix.

For More Information

The package apache2-doc contains the complete Apache manual in various localizations for local installation and reference. It is not installed by default—the quickest way to install it is to use the command zypper in apache2-doc. Once installed, the Apache manual is available at http://localhost/manual/. You may also access it on the Web at http://httpd.apache.org/docs-2.2/. SUSE-specific configuration hints are available in the directory /usr/share/doc/packages/apache2/README.*.

Apache 2.2

For a list of new features in Apache 2.2, refer to http://httpd.apache.org/docs/2.2/new_features_2_2.html. Information about upgrading from version 2.0 to 2.2 is available at http://httpd.apache.org/docs-2.2/upgrading.html.

Apache Modules

More information about external Apache modules from Section “External Modules” is available at the following locations:

mod-apparmor

http://en.opensuse.org/AppArmor

mod_mono

http://www.mono-project.com/Mod_mono

mod_perl

http://perl.apache.org/

mod_php5

http://www.php.net/manual/en/install.unix.apache2.php

mod_python

http://www.modpython.org/

mod_tidy

http://mod-tidy.sourceforge.net/

Development

More information about developing Apache modules or about getting involved in the Apache Web server project are available at the following locations:

Apache Developer Information

http://httpd.apache.org/dev/

Apache Developer Documentation

http://httpd.apache.org/docs/2.2/developer/

Writing Apache Modules with Perl and C

http://www.modperl.com/

Miscellaneous Sources

If you experience difficulties specific to Apache in openSUSE, take a look at the openSUSE wiki at http://en.opensuse.org/Apache. The history of Apache is provided at http://httpd.apache.org/ABOUT_APACHE.html. This page also explains why the server is called Apache.

Chapter 29. Setting up an FTP server with YaST

Abstract

Using the YaST FTP Server module, you can configure your machine to function as an FTP server. Anonymous and/or authenticated users can connect to your machine and download and, depending on the configuration, upload files using the FTP protocol. YaST provides a unified configuration interface for various FTP server daemons installed on your system.

The YaST FTP Server configuration module can be used to configure two different FTP server daemons: vsftpd (Very Secure FTP Daemon) and pure-ftpd. Only installed servers can be configured. Standard openSUSE media does not contain the pure-ftpd package. However, if the pure-ftpd package is installed from another repository, it can be configured using the YaST module.

The vsftpd and pure-ftpd servers have slightly different configuration options, especially in the Experts Settings dialog. This chapter describes the settings of the vsftpd for being the default server for openSUSE server .

If the YaST FTP Server module is not available in your system, install the yast2-ftp-server package.

To configure the FTP server using YaST, follow these steps:

Open YaST Control Center and choose Network Services+FTP Server or run the yast2 ftp-server command as root.

If there is not any FTP server installed in your system, you will be asked which server to install when the YaST FTP Server module starts. Choose a server (vsftpd is the standard server for openSUSE) and confirm the dialog.

In the Start-Up dialog, configure the starting of the FTP server. For more information, see Section “Starting the FTP server”.

In the General dialog, configure FTP directories, welcome message, file creation masks and various other parameters. For more information, see Section “FTP General Settings”.

In the Performance dialog, set the parameters that affect the load on the FTP server. For more information, see Section “FTP Performance Settings”.

In the Authentication dialog, set whether the FTP server should be available for anonymous and/or authenticated users. For more information, see Section “Authentication”.

In the Expert Settings dialog, configure the operation mode of the FTP server, SSL connections and firewall settings. For more information, see Section “Expert Settings”.

Press Finish to save the configurations.

Starting the FTP server

In the Service Start frame of the FTP Start-Up dialog set the way the FTP server is started up. You can choose between starting the server automatically during the system boot and starting it manually. If the FTP server should be started only after FTP connection request, choose Via xinetd.

The current status of the FTP server is shown in the Switch On and Off frame of the FTP Start-Up dialog. Start the FTP server by pressing Start FTP Now. To stop the server, press Stop FTP Now. After having changed the settings of the server press Save Settings and Restart FTP Now. Your configurations will be saved by leaving the configuration module with Finish, as well.

The Selected Service frame of the FTP Start-Up dialog shows which FTP server is used. Either vsftpd (Very Secure FTP Daemon) or pure-ftpd can be used. If both servers are installed, you can switch between them—the current configuration will automatically be converted. The pure-ftpd package is not included in the standard openSUSE media so you have to install it from a different installation source if you want to use it.

Figure 29.1. FTP Server Configuration — Start-Up

FTP General Settings

In the General Settings frame of the FTP General Settings dialog you can set the Welcome message which is shown after connecting to the FTP server.

If you check the Chroot Everyone option, all local users will be placed in a chroot jail in their home directory after login. This option has security implications, especially if the users have upload permission or shell access, so be careful enabling this option.

If you check the Verbose Logging option, all FTP requests and responses are logged.

You can limit permissions of files created by anonymous and/or authenticated users with umask. The bits that are set in the umask identify permissions that are always to be disabled for newly created files. Set the file creation mask for anonymous users in Umask for Anonymous and the file creation mask for authenticated users in Umask for Authenticated Users. The masks should be entered as octal numbers with a leading zero. For more information about umask, see the umask man page (man 1p umask.

In the FTP Directories frame set the directories used for anonymous and authorized users. By pressing Browse, you can select a directory to be used from the local filesystem. The default FTP directory for anonymous users is /srv/ftp. Note that vsftpd does not allow this directory to be writable for all users. The subdirectory upload with write permissions for anonymous users is created instead.

Note

The pure-ftpd server allows the FTP directory for anonymous users to be writable. When switching between servers, make sure you remove the write permissions in the directory that was used with pure-ftpd before switching back to the vsftpd server.

FTP Performance Settings

In the Performance dialog set the parameters which affect the load on the FTP server. Max Idle Time is the maximum time (in minutes) the remote client may spend between FTP commands. In case of longer inactivity, the remote client is disconnected. Max Clients for One IP determines the maximum number of clients which can be connected from a single IP address. Max Clients determines the maximum number of clients which may be connected. Any additional clients will get an error message.

The maximum data transfer rate (in KB/s) is set in Local Max Rate for local authenticated users, and in Anonymous Max Rate for anonymous clients respectively. The default value for the rate settings is 0, which means unlimited data transfer rate.

Authentication

In the Enable/Disable Anonymous and Local Users frame of the Authentication dialog, you are able to set which users are allowed to access your FTP server. You can grant access only for anonymous users, only for authenticated users with accounts on the system or for both types of users.

If you want to allow users to upload files to the FTP server, check Enable Upload in the Uploading frame of the Authentication dialog. Here you are able to allow uploading or creating directories even for anonymous users by checking the respective box.

Note

If a vsftpd server is used and you want anonymous users to be able to upload files or create directories, a subdirectory with writing permissions for all users has to be created in the anonymous FTP directory.

Expert Settings

An FTP server can run in active or in passive mode. By default the server runs in passive mode. To switch into active mode, just uncheck Enable Passive Mode option in Expert Settings dialog. You can also change the range of ports on the server used for the data stream by tweaking the Min Port for Pas. Mode and Max Port for Pas. Mode options.

If you want encrypted communication between clients and the server, you can use the FTPS protocol (FTP/SSH). However note that FTPS is different from the much more common SFTP (SSH File Transport Protocol) protocol. If you want to use the FTPS, you can set SSL options in the Expert Settings dialog.

If your system is protected by a firewall, check Open Port in Firewall to enable a connection to the FTP server.

For more information

For more information about ftp servers read the manual pages of vsftpd and vsftpd.conf.

Part VI. Mobility

Chapter 30. Mobile Computing with Linux

Abstract

Mobile computing is mostly associated with laptops, PDAs and cellular phones (and the data exchange between them). Mobile hardware components, such as external hard disks, flash drives, or digital cameras, can be connected to laptops or desktop systems. A number of software components are involved in mobile computing scenarios and some applications are tailor-made for mobile use.

Laptops

The hardware of laptops differs from that of a normal desktop system. This is because criteria like exchangeability, space requirements and power consumption must be taken into account. The manufacturers of mobile hardware have developed standard interfaces like PCMCIA (Personal Computer Memory Card International Association), Mini PCI and Mini PCIe that can be used to extend the hardware of laptops. The standards cover memory cards, network interface cards, ISDN (and modem cards) and external hard disks.

openSUSE and Tablet PCs

openSUSE also supports Tablet PCs. Tablet PCs come with a touchpad/digitizer that allows you to use a digital pen or even fingertips to edit data right on the screen instead of using mouse and keyboard. They are installed and configured much like any other system. For a detailed introduction to the installation and configuration of Tablet PCs, refer to Chapter 33, Using Tablet PCs.

Power Conservation

The inclusion of energy-optimized system components during laptop manufacturing contributes to their suitability for use without access to the electrical power grid. Their contribution towards conservation of power is at least as important as that of the operating system. openSUSE® supports various methods that influence the power consumption of a laptop and have varying effects on the operating time under battery power. The following list is in descending order of contribution towards power conservation:

Throttling the CPU speed.

Switching off the display illumination during pauses.

Manually adjusting the display illumination.

Disconnecting unused, hotplug-enabled accessories (USB CD-ROM, external mouse, unused PCMCIA cards, WLAN, etc.).

Spinning down the hard disk when idling.

Detailed background information about power management in openSUSE is provided in Chapter 31, Power Management. For more information desktop specific power management, see the “Controlling Your Desktop’s Power Management” (Chapter “Working with Your Desktop”, ↑GNOME User Guide) on how to use the GNOME Power Manager. More information about the KDE power management applet is available at “Controlling Your Desktop’s Power Management” (↑KDE User Guide).

Integration in Changing Operating Environments

Your system needs to adapt to changing operating environments when used for mobile computing. Many services depend on the environment and the underlying clients must be reconfigured. openSUSE handles this task for you.

Figure 30.1. Integrating a Mobile Computer in an Existing Environment

The services affected in the case of a laptop commuting back and forth between a small home network and an office network are:

Network

This includes IP address assignment, name resolution, Internet connectivity and connectivity to other networks.

Printing

A current database of available printers and an available print server must be present, depending on the network.

E-Mail and Proxies

As with printing, the list of the corresponding servers must be current.

X (Graphical Environment)

If your laptop is temporarily connected to a projector or an external monitor, the different display configurations must be available.

openSUSE offers several ways of integrating laptops into existing operating environments:

NetworkManager

NetworkManager is especially tailored for mobile networking on laptops. It provides a means to easily and automatically switch between network environments or different types of networks, such as wireless LAN and ethernet. NetworkManager supports WEP and WPA-PSK encryption in wireless LANs. It also supports dial-up connections (with smpppd). Both desktop environments (GNOME and KDE) include a front-end for NetworkManager. For more information about the desktop applets, see “Using KNetworkManager” (Chapter “Using NetworkManager”, ↑Start-Up) and “Using GNOME NetworkManager Applet” (Chapter “Using NetworkManager”, ↑Start-Up).

Table 30.1. Use Cases for NetworkManager

My computer…

Use NetworkManager

is a laptop

Yes

is sometimes attached to different networks

Yes

provides network services (such as DNS or DHCP)

No

only uses a static IP address

No

Use the YaST tools to configure networking whenever NetworkManager should not handle network configuration.

SCPM

SCPM (system configuration profile management) allows storage of arbitrary configuration states of a system into a kind of “snapshot” called a profile. Profiles can be created for different situations. They are useful when a system is operating in changing environments (home network, office network). It is always possible to switch between profiles. To get SCPM up and running on your system, install the package scpm. Enable SCPM using the YaST Profile Management module and configure the users that should be allowed to switch profiles without the need of entering the root password. Determine whether profile changes should survive a system reboot or whether they should be discarded upon shutdown. Make sure all resource groups (i.e. services like network and printer, for example) are active. Proceed to creating actual profiles using scpm command line tool. Refer to the scpm man page for details. Create profiles for all the different setups you want to use this system in. Switching between profiles can either be done on the running system via scpm switch PROFILENAME or at system boot time via the F3 key. When switching profiles, SCPM automatically adjusts your system configuration to the new environment laid out in the profile you have chosen.

Under KDE, a GUI for scpm is available. Make sure the package kscpm is installed. Start the Profile Management via Applications+System+Configuration from the KDE Main Menu. The Profile Management tools lets you create and manage profiles. You can switch profiles by using the Profile Management applet in the system tray.

SLP

The service location protocol (SLP) simplifies the connection of a laptop to an existing network. Without SLP, the administrator of a laptop usually requires detailed knowledge of the services available in a network. SLP broadcasts the availability of a certain type of service to all clients in a local network. Applications that support SLP can process the information dispatched by SLP and be configured automatically. SLP can even be used for the installation of a system, sparing the effort of searching for a suitable installation source. Find detailed information about SLP in Chapter 22, SLP Services in the Network.

Software Options

There are various special task areas in mobile use that are covered by dedicated software: system monitoring (especially the battery charge), data synchronization, and wireless communication with peripherals and the Internet. The following sections cover the most important applications that openSUSE provides for each task.

System Monitoring

Two KDE system monitoring tools are provided by openSUSE:

KPowersave

KPowersave is an applet that displays the state of the rechargeable battery in the control panel. The icon adjusts to represent the type of power supply. When working on AC power, a small plug icon is displayed. When working on batteries, the icon changes to a battery.

Right-click the KPowersave tray icon to access options to configure KPowersave behavior. You can choose one of four listed schemes, according to your needs. For example, the Presentation scheme disables the screen saver and the power management in general, so that your presentation is not interrupted by system events. You can also tell the system what to do if, for example, you close the laptop lid or press the power button.

KSysguard

KSysguard is an independent application that gathers all measurable parameters of the system into one monitoring environment. KSysguard has monitors for ACPI (battery status), CPU load, network, partitioning and memory usage. It can also watch and display all system processes. The presentation and filtering of the collected data can be customized. It is possible to monitor different system parameters in various data pages or collect the data of various machines in parallel over the network. KSysguard can also run as a daemon on machines without a KDE environment. Find more information about this program in its integrated help function or in the SUSE help pages.

In the GNOME desktop, use GNOME Power Management Preferences and System Monitor.

Synchronizing Data

When switching between working on a mobile machine disconnected from the network and working at a networked workstation in an office, it is necessary to keep processed data synchronized across all instances. This could include e-mail folders, directories and individual files that need to be present for work on the road as well as at the office. The solution in both cases is as follows:

Synchronizing E-Mail

Use an IMAP account for storing your e-mails in the office network. Then access the e-mails from the workstation using any disconnected IMAP–enabled e-mail client, like Mozilla Thunderbird Mail, Evolution, or KMail as described in “GNOME User Guide” (↑GNOME User Guide) and “KDE User Guide” (↑KDE User Guide). The e-mail client must be configured so that the same folder is always accessed for Sent messages. This ensures that all messages are available along with their status information after the synchronization process has completed. Use an SMTP server implemented in the mail client for sending messages instead of the systemwide MTA postfix or sendmail to receive reliable feedback about unsent mail.

Synchronizing Files and Directories

There are several utilities suitable for synchronizing data between a laptop and a workstation. For detailed information, refer to Chapter 34, Copying and Sharing Files.

Wireless Communication

As well as connecting to a home or office network with a cable, a laptop can also wirelessly connect to other computers, peripherals, cellular phones or PDAs. Linux supports three types of wireless communication:

WLAN

With the largest range of these wireless technologies, WLAN is the only one suitable for the operation of large and sometimes even spatially disjointed networks. Single machines can connect with each other to form an independent wireless network or access the Internet. Devices called access points act as base stations for WLAN-enabled devices and act as intermediaries for access to the Internet. A mobile user can switch among access points depending on location and which access point is offering the best connection. Like in cellular telephony, a large network is available to WLAN users without binding them to a specific location for accessing it. Find details about WLAN in Chapter 32, Wireless LAN.

Bluetooth

Bluetooth has the broadest application spectrum of all wireless technologies. It can be used for communication between computers (laptops) and PDAs or cellular phones, as can IrDA. It can also be used to connect various computers within range. Bluetooth is also used to connect wireless system components, like a keyboard or mouse. The range of this technology is, however, not sufficient to connect remote systems to a network. WLAN is the technology of choice for communicating through physical obstacles like walls.

IrDA

IrDA is the wireless technology with the shortest range. Both communication parties must be within viewing distance of each other. Obstacles like walls cannot be overcome. One possible application of IrDA is the transmission of a file from a laptop to a cellular phone. The short path from the laptop to the cellular phone is then covered using IrDA. The long range transport of the file to the recipient of the file is handled by the mobile network. Another application of IrDA is the wireless transmission of printing jobs in the office.

Data Security

Ideally, you protect data on your laptop against unauthorized access in multiple ways. Possible security measures can be taken in the following areas:

Protection against Theft

Always physically secure your system against theft whenever possible. Various securing tools (like chains) are available in retail stores.

Strong Authentication

Use biometric authentication in addition to standard authentication via login and password. openSUSE supports fingerprint authentication. For more details, see “Using the Fingerprint Reader” (↑Security Guide).

Securing Data on the System

Important data should not only be encrypted during transmission, but also on the hard disk. This ensures its safety in case of theft. The creation of an encrypted partition with openSUSE is described in “Encrypting Partitions and Files” (↑Security Guide). Another possibility is to create encrypted home directories when adding the user with YaST.

Data Security and Suspend to Disk

Encrypted partitions are not unmounted during a suspend to disk event. Thus, all data on these partitions is available to any party who manages to steal the hardware and issue a resume of the hard disk.

Network Security

Any transfer of data should be secured, no matter how the transfer is done. Find general security issues regarding Linux and networks in “Security and Confidentiality” (↑Security Guide). Security measures related to wireless networking are provided in Chapter 32, Wireless LAN.

Mobile Hardware

openSUSE supports the automatic detection of mobile storage devices over FireWire (IEEE 1394) or USB. The term mobile storage device applies to any kind of FireWire or USB hard disk, USB flash drive, or digital camera. These devices are automatically detected and configured as soon as they are connected with the system over the corresponding interface. The file managers of both GNOME and KDE offer flexible handling of mobile hardware items. To unmount any of these media safely, use the Safely Remove (KDE) or Unmount (GNOME) feature of either file manager. The handling of removable media by your desktop is described in more detail in “GNOME User Guide” (↑GNOME User Guide) and “KDE User Guide” (↑KDE User Guide).

External Hard Disks (USB and FireWire)

As soon as an external hard disk is correctly recognized by the system, its icon appears in the file manager. Clicking the icon displays the contents of the drive. It is possible to create folders and files here and edit or delete them. To rename a hard disk from the name it had been given by the system, select the corresponding menu item from the menu that opens when the icon is right-clicked. This name change is limited to display in the file manager. The descriptor by which the device is mounted in /media remains unaffected by this.

USB Flash Drives

These devices are handled by the system just like external hard disks. It is similarly possible to rename the entries in the file manager.

Digital Cameras (USB and FireWire)

Digital cameras recognized by the system also appear as external drives in the overview of the file manager. KDE allows reading and accessing the pictures at the URL camera:/ . The images can then be processed using digiKam or f-spot. For advanced photo processing, use GIMP. For a short introduction to digiKam, f-spot and GIMP, see “Managing Your Digital Image Collection with DigiKam” (↑Application Guide), “Managing Your Digital Image Collection with F-Spot” (↑Application Guide) and “Manipulating Graphics with GIMP” (↑Application Guide).

Cellular Phones and PDAs

A desktop system or a laptop can communicate with a cellular phone via Bluetooth or IrDA. Some models support both protocols and some only one of the two. The usage areas for the two protocols and the corresponding extended documentation has already been mentioned in Section “Wireless Communication”. The configuration of these protocols on the cellular phones themselves is described in their manuals.

The support for synchronizing with handheld devices manufactured by Palm, Inc., is already built into Evolution and Kontact. Initial connection with the device is, in both cases, easily performed with the assistance of a wizard. Once the support for Palm Pilots is configured, it is necessary to determine which type of data should be synchronized (addresses, appointments, etc.). For more information, see “GNOME User Guide” (↑GNOME User Guide) and “KDE User Guide” (↑KDE User Guide).

A more sophisticated synchronization solution is available with the program opensync (see packages libopensync, msynctool and the respective plug-ins for the different devices).

For More Information

The central point of reference for all questions regarding mobile devices and Linux is http://tuxmobil.org/. Various sections of that Web site deal with the hardware and software aspects of laptops, PDAs, cellular phones and other mobile hardware.

A similar approach to that of http://tuxmobil.org/ is made by http://www.linux-on-laptops.com/. Information about laptops and handhelds can be found here.

SUSE maintains a mailing list in German dedicated to the subject of laptops. See http://lists.opensuse.org/opensuse-mobile-de/. On this list, users and developers discuss all aspects of mobile computing with openSUSE. Postings in English are answered, but the majority of the archived information is only available in German. Use http://lists.opensuse.org/opensuse-mobile/ for English postings.

Information about OpenSync is available on http://en.opensuse.org/OpenSync.

Chapter 31. Power Management

Power management is especially important on laptop computers, but is also useful on other systems. ACPI (advanced configuration and power interface) is available on all modern computers (laptops, desktops, and servers). Power management technologies require suitable hardware and BIOS routines. Most laptops and many modern desktops and servers meet these requirements. It is also possible to control CPU frequency scaling to save power or decrease noise.

Power Saving Functions

Power saving functions are not only significant for the mobile use of laptops, but also for desktop systems. The main functions and their use in ACPI are:

Standby

not supported.

Suspend (to memory)

This mode writes the entire system state to the RAM. Subsequently, the entire system except the RAM is put to sleep. In this state, the computer consumes very little power. The advantage of this state is the possibility of resuming work at the same point within a few seconds without having to boot and restart applications. This function corresponds to the ACPI state S3. The support of this state is still under development and therefore largely depends on the hardware.

Hibernation (suspend to disk)

In this operating mode, the entire system state is written to the hard disk and the system is powered off. There must be a swap partition at least as big as the RAM to write all the active data. Reactivation from this state takes about 30 to 90 seconds. The state prior to the suspend is restored. Some manufacturers offer useful hybrid variants of this mode, such as RediSafe in IBM Thinkpads. The corresponding ACPI state is S4. In Linux, suspend to disk is performed by kernel routines that are independent from ACPI.

Battery Monitor

ACPI checks the battery charge status and provides information about it. Additionally, it coordinates actions to perform when a critical charge status is reached.

Automatic Power-Off

Following a shutdown, the computer is powered off. This is especially important when an automatic shutdown is performed shortly before the battery is empty.

Processor Speed Control

In connection with the CPU, energy can be saved in three different ways: frequency and voltage scaling (also known as PowerNow! or Speedstep), throttling and putting the processor to sleep (C states). Depending on the operating mode of the computer, these methods can also be combined.

ACPI

ACPI (advanced configuration and power interface) was designed to enable the operating system to set up and control the individual hardware components. ACPI supersedes both PnP and APM. It delivers information about the battery, AC adapter, temperature, fan and system events, like “close lid” or “battery low.”

The BIOS provides tables containing information about the individual components and hardware access methods. The operating system uses this information for tasks like assigning interrupts or activating and deactivating components. Because the operating system executes commands stored in the BIOS, the functionality depends on the BIOS implementation. The tables ACPI can detect and load are reported in /var/log/boot.msg. See Section “Troubleshooting” for more information about troubleshooting ACPI problems.

Controlling the CPU Performance

The CPU can save energy in three ways. Depending on the operating mode of the computer, these methods can be combined. Saving energy also means that the system heats up less and the fans are activated less frequently.

Frequency and Voltage Scaling

PowerNow! and Speedstep are the designations AMD and Intel use for this technology. However, this technology is also applied in processors of other manufacturers. The clock frequency of the CPU and its core voltage are reduced at the same time, resulting in more than linear energy savings. This means that when the frequency is halved (half performance), far less than half of the energy is consumed. This technology is independent from ACPI. There are two main approaches to performing CPU frequency scaling—by the kernel itself or by a userspace application. Therefore, there are different kernel governors that can be set below /sys/devices/system/cpu/cpu*/cpufreq/.

userspace governor

If the userspace governor is set, the kernel gives the control of CPU frequency scaling to a userspace application, usually a daemon. In openSUSE distributions, this daemon is the powersaved package. When this implementation is used, the CPU frequency is adjusted in regard to the current system load. By default, one of the kernel implementations is used. However, on some hardware or in regard to specific processors or drivers, the userspace implementation is still the only working solution.

ondemand governor

This is the kernel implementation of a dynamic CPU frequency policy and should work on most systems. As soon as there is a high system load, the CPU frequency is immediately increased. It is lowered on a low system load.

conservative governor

This governor is similar to the on demand implementation, except that a more conservative policy is used. The load of the system must be high for a specific amount of time before the CPU frequency is increased.

powersave governor

The cpu frequency is statically set to the lowest possible.

performance governor

The cpu frequency is statically set to the highest possible.

Throttling the Clock Frequency

This technology omits a certain percentage of the clock signal impulses for the CPU. At 25% throttling, every fourth impulse is omitted. At 87.5%, only every eighth impulse reaches the processor. However, the energy savings are a little less than linear. Normally, throttling is only used if frequency scaling is not available or to maximize power savings. This technology must be controlled by a special process, as well. The system interface is /proc/acpi/processor/*/throttling.

Putting the Processor to Sleep

The operating system puts the processor to sleep whenever there is no activity. In this case, the operating system sends the CPU a halt command. There are three states: C1, C2, and C3. In the most economic state, C3, even the synchronization of the processor cache with the main memory is halted. Therefore, this state can only be applied if no other device modifies the contents of the main memory via bus master activity. Some drivers prevent the use of C3. The current state is displayed in /proc/acpi/processor/*/power.

Frequency scaling and throttling are only relevant if the processor is busy, because the most economic C state is applied anyway when the processor is idle. If the CPU is busy, frequency scaling is the recommended power saving method. Often the processor only works with a partial load. In this case, it can be run with a lower frequency. Usually, dynamic frequency scaling controlled by the kernel on demand governor or a daemon, such as powersaved, is the best approach. A static setting to a low frequency is useful for battery operation or if you want the computer to run cool or be quiet.

Throttling should be used as the last resort, for example, to extend the battery operation time despite a high system load. However, some systems do not run smoothly when they are throttled too much. Moreover, CPU throttling does not make sense if the CPU has little to do.

ACPI Tools

The range of more or less comprehensive ACPI utilities includes tools that merely display information, like the battery charge level and the temperature (acpi, klaptopdaemon, etc.), tools that facilitate the access to the structures in /proc/acpi/ or that assist in monitoring changes (akpi, acpiw, gtkacpiw) and tools for editing the ACPI tables in the BIOS (package acpica).

Troubleshooting

There are two different types of problems. On one hand, the ACPI code of the kernel may contain bugs that were not detected in time. In this case, a solution will be made available for download. More often, the problems are caused by the BIOS. Sometimes, deviations from the ACPI specification are purposely integrated in the BIOS to circumvent errors in the ACPI implementation of other widespread operating systems. Hardware components that have serious errors in the ACPI implementation are recorded in a blacklist that prevents the Linux kernel from using ACPI for these components.

The first thing to do when problems are encountered is to update the BIOS. If the computer does not boot at all, one of the following boot parameters may be helpful:

pci=noacpi

Do not use ACPI for configuring the PCI devices.

acpi=ht

Only perform a simple resource configuration. Do not use ACPI for other purposes.

acpi=off

Disable ACPI.

Problems Booting without ACPI

Some newer machines (especially SMP systems and AMD64 systems) need ACPI for configuring the hardware correctly. On these machines, disabling ACPI can cause problems.

Sometimes, the machine is confused by hardware that is attached over USB or FireWire. If a machine refuses to boot, unplug all unneeded hardware and try again.

Monitor the boot messages of the system with the command dmesg | grep -2i acpi (or all messages, because the problem may not be caused by ACPI) after booting. If an error occurs while parsing an ACPI table, the most important table—the DSDT (Differentiaed System Description Table)—can be replaced with an improved version. In this case, the faulty DSDT of the BIOS is ignored. The procedure is described in Section “Troubleshooting”.

In the kernel configuration, there is a switch for activating ACPI debug messages. If a kernel with ACPI debugging is compiled and installed, experts searching for an error can be supported with detailed information.

If you experience BIOS or hardware problems, it is always advisable to contact the manufacturers. Especially if they do not always provide assistance for Linux, they should be confronted with the problems. Manufacturers will only take the issue seriously if they realize that an adequate number of their customers use Linux.

Rest for the Hard Disk

In Linux, the hard disk can be put to sleep entirely if it is not needed or it can be run in a more economic or quieter mode. On modern laptops, you do not need to switch off the hard disks manually, because they automatically enter an economic operating mode whenever they are not needed. However, if you want to maximize power savings, test some of the following methods.

The hdparm application can be used to modify various hard disk settings, both for PATA and SATA disks. The option -y instantly switches the hard disk to the standby mode. -Y puts it to sleep. hdparm -S x causes the hard disk to be spun down after a certain period of inactivity. Replace x as follows: 0 disables this mechanism, causing the hard disk to run continuously. Values from 1 to 240 are multiplied by 5 seconds. Values from 241 to 251 correspond to 1 to 11 times 30 minutes.

Internal power saving options of the hard disk can be controlled with the option -B. Select a value from 0 to 255 for maximum saving to maximum throughput. The result depends on the hard disk used and is difficult to assess. To make a hard disk quieter, use the option -M. Select a value from 128 to 254 for quiet to fast.

Often, it is not so easy to put the hard disk to sleep. In Linux, numerous processes write to the hard disk, waking it up repeatedly. Therefore, it is important to understand how Linux handles data that needs to be written to the hard disk. First, all data is buffered in the RAM. This buffer is monitored by the pdflush daemon. When the data reaches a certain age limit or when the buffer is filled to a certain degree, the buffer content is flushed to the hard disk. The buffer size is dynamic and depends on the size of the memory and the system load. By default, pdflush is set to short intervals to achieve maximum data integrity. It checks the buffer every 5 seconds and writes the data to the hard disk. The following variables are interesting:

/proc/sys/vm/dirty_writeback_centisecs

Contains the delay until a pdflush thread wakes up (in hundreths of a second).

/proc/sys/vm/dirty_expire_centisecs

Defines after which timeframe a dirty page should be written out latest. Default is 3000, which means 30 seconds.

/proc/sys/vm/dirty_background_ratio

Maximum percentage of dirty pages until pdflush begins to write them. Default is 5%.

/proc/sys/vm/dirty_ratio

When the dirty page exceeds this percentage of the total memory, processes are forced to write dirty buffers during their time slice instead of continuing to write.

Impairment of the Data Integrity

Changes to the pdflush daemon settings endanger the data integrity.

Apart from these processes, journaling file systems, like ReiserFS, Ext3, Ext4 and others write their metadata independently from pdflush, which also prevents the hard disk from spinning down. To avoid this, a special kernel extension has been developed for mobile devices. See /usr/src/linux/Documentation/laptop-mode.txt for details.

Another important factor is the way active programs behave. For example, good editors regularly write hidden backups of the currently modified file to the hard disk, causing the disk to wake up. Features like this can be disabled at the expense of data integrity.

In this connection, the mail daemon postfix makes use of the variable POSTFIX_LAPTOP. If this variable is set to yes, postfix accesses the hard disk far less frequently.

Troubleshooting

All error messages and alerts are logged in the file /var/log/messages. If you cannot find the needed information, increase the verbosity of the messages of powersave using DEBUG in the file /etc/sysconfig/powersave/common. Increase the value of the variable to 7 or even 15 and restart the daemon. The more detailed error messages in /var/log/messages should help you to find the error. The following sections cover the most common problems with powersave and the different sleep modes.

ACPI Activated with Hardware Support but Functions Do Not Work

If you experience problems with ACPI, use the command dmesg|grep -i acpi to search the output of dmesg for ACPI-specific messages. A BIOS update may be required to resolve the problem. Go to the home page of your laptop manufacturer, look for an updated BIOS version, and install it. Ask the manufacturer to comply with the latest ACPI specification. If the errors persist after the BIOS update, proceed as follows to replace the faulty DSDT table in your BIOS with an updated DSDT:

Download the DSDT for your system from http://acpi.sourceforge.net/dsdt/index.php. Check if the file is decompressed and compiled as shown by the file extension .aml (ACPI machine language). If this is the case, continue with step 3.

If the file extension of the downloaded table is .asl (ACPI source language), compile it with iasl (package acpica). Enter the command iasl -sa file.asl.

Copy the file DSDT.aml to any location (/etc/DSDT.aml is recommended). Edit /etc/sysconfig/kernel and adapt the path to the DSDT file accordingly. Start mkinitrd (package mkinitrd). Whenever you install the kernel and use mkinitrd to create an initrd, the modified DSDT is integrated and loaded when the system is booted.

CPU Frequency Does Not Work

Refer to the kernel sources (kernel-source) to see if your processor is supported. You may need a special kernel module or module option to activate CPU frequency control. This information is available in /usr/src/linux/Documentation/cpu-freq/*.

Suspend and Standby Do Not Work

ACPI systems may have problems with suspend and standby due to a faulty DSDT implementation (BIOS). If this is the case, update the BIOS.

When the system tries to unload faulty modules, the system is arrested or the suspend event is not triggered. The same can also happen if you do not unload modules or stop services that prevent a successful suspend. In both cases, try to identify the faulty module that prevented the sleep mode. The log file /var/log/pm-suspend.log contains detailed information about what is going on and where possible errors are. Modify the SUSPEND_MODULES variable in /usr/lib/pm-utils/defaults to unload problematic modules prior to a suspend or standby.

Refer to http://en.opensuse.org/Pm-utils and http://en.opensuse.org/S2ram to get more detailed information on how to modify the suspend and resume process.

For More Information

http://www.intel.com/technology/iapc/acpi/index.htm (Advanced Configuration & Power Interface)

http://www.lesswatts.org/projects/acpi/ (the ACPI4Linux project at Sourceforge)

http://www.poupinou.org/acpi/ (DSDT patches by Bruno Ducrot)

http://en.opensuse.org/S2ram—How to get Suspend to RAM working

http://www.opensuse.org/Pm-utils—How to modify the general suspend framework

Chapter 32. Wireless LAN

Abstract

Wireless LANs, or Wireless Local Area Network (WLANs), have become an indispensable aspect of mobile computing. Today, most laptops have built-in WLAN cards. This chapter describes how to set up a WLAN card with YaST, encrypt transmissions, and use tips and tricks.

WLAN Standards

WLAN cards communicate using the 802.11 standard, prepared by the IEEE organization. Originally, this standard provided for a maximum transmission rate of 2 Mbit/s. Meanwhile, several supplements have been added to increase the data rate. These supplements define details such as the modulation, transmission output, and transmission rates (see Table 32.1, “Overview of Various WLAN Standards”). Additionally, many companies implement hardware with proprietary or draft features.

Table 32.1. Overview of Various WLAN Standards

Name

Band (GHz)

Maximum Transmission Rate (Mbit/s)

Note

802.11 Legacy

2.4

2

Outdated; virtually no end devices available

802.11a

5

54

Less interference-prone

802.11b

2.4

11

Less common

802.11g

2.4

54

Widespread, backwards-compatible with 11b

802.11n (formerly 802.11n draft)

2.4 and/or 5

300

Common

802.11 Legacy cards are not supported by openSUSE®. Most cards using 802.11a, 802.11b, 802.11g and 802.11n draft are supported. New cards usually comply with the 802.11n draft standard, but cards using 802.11g are still available.

Operating Modes

In wireless networking, various techniques and configurations are used to ensure fast, high-quality, and secure connections. Different operating types suit different setups. It can be difficult to choose the right authentication method. The available encryption methods have different advantages and pitfalls.

Basically, wireless networks can be classified into two network modes:

Managed

Managed networks have a managing element: the access point. In this mode (also referred to as infrastructure mode), all connections of the WLAN stations in the network run through the access point, which may also serve as a connection to an ethernet.

Ad-hoc

Ad-hoc networks do not have an access point. The stations communicate directly with each other, therefore an ad-hoc network is usually faster than a managed network. However, the transmission range and number of participating stations are greatly limited in ad-hoc networks. They also do not support WPA authentication. Therefore, an access point is usually used. It is even possible to use a WLAN card as an access point. Some cards support this functionality.

Master

In master mode your network card is used as the access point. It works only if your WLAN card supports this mode. Find out the details of your WLAN card on http://linux-wless.passys.nl.

Authentication

Because a wireless network is much easier to intercept and compromise than a wired network, the various standards include authentication and encryption methods. In the original version of the IEEE 802.11 standard, these are described under the term WEP (Wired Equivalent Privacy). However, because WEP has proven to be insecure (see Section “Security”), the WLAN industry (joined under the name Wi-Fi Alliance) has defined an extension called WPA, which is supposed to eliminate the weaknesses of WEP. The later IEEE 802.11i standard (also referred to as WPA2, because WPA is based on a draft version of 802.11i) includes WPA and some other authentication and encryption methods.

To make sure that only authorized stations can connect, various authentication mechanisms are used in managed networks:

None (Open)

An open system is a system that does not require authentication. Any station can join the network. Nevertheless, WEP encryption (see Section “Encryption”) can be used.

Shared Key (according to IEEE 802.11)

In this procedure, the WEP key is used for the authentication. However, this procedure is not recommended, because it makes the WEP key more susceptible to attacks. All an attacker needs to do is to listen long enough to the communication between the station and the access point. During the authentication process, both sides exchange the same information, once in encrypted form and once in unencrypted form. This makes it possible for the key to be reconstructed with suitable tools. Because this method makes use of the WEP key for the authentication and for the encryption, it does not enhance the security of the network. A station that has the correct WEP key can authenticate, encrypt, and decrypt. A station that does not have the key cannot decrypt received packets. Accordingly, it cannot communicate, regardless of whether it had to authenticate itself.

WPA-PSK, sometimes WPA-Personal (according to IEEE 802.1x)

WPA-PSK (PSK stands for preshared key) works similarly to the Shared Key procedure. All participating stations as well as the access point need the same key. The key is 256 bits in length and is usually entered as a passphrase. This system does not need a complex key management like WPA-EAP and is more suitable for private use. Therefore, WPA-PSK is sometimes referred to as WPA “Home”.

WPA-EAP, sometimes WPA-Enterprise (according to IEEE 802.1x)

Actually, WPA-EAP (Extensible Authentication Protocol) is not an authentication system but a protocol for transporting authentication information. WPA-EAP is used to protect wireless networks in enterprises. In private networks, it is scarcely used. For this reason, WPA-EAP is sometimes referred to as WPA “Enterprise”.

WPA-EAP needs a Radius server to authenticate users. EAP offers three different methods for connecting and authenticating to the server: TLS (Transport Layer Security), TTLS (Tunneled Transport Layer Security), and PEAP (Protected Extensible Authentication Protocol). In a nutshell, these options work as follows:

EAP-TLS

TLS authentication relies on the mutual exchange of certificates for both server and client. First, the server presents its certificate to the client where it is evaluated. If the certificate is considered valid, the client in turn presents its certificate to the server. While TLS is secure, it requires a working certification management infrastructure in your network. This infrastructure is rarely found in private networks.

EAP-TTLS and PEAP

Both TTLS and PEAP are two-stage protocols. In the first stage, a secure connection is established and in the second the client authentication data is exchanged. They require far less certification management overhead than TLS, if any.

Encryption

There are various encryption methods to ensure that no unauthorized person can read the data packets that are exchanged in a wireless network or gain access to the network:

WEP (defined in IEEE 802.11)

This standard makes use of the RC4 encryption algorithm, originally with a key length of 40 bits, later also with 104 bits. Often, the length is declared as 64 bits or 128 bits, depending on whether the 24 bits of the initialization vector are included. However, this standard has some weaknesses. Attacks against the keys generated by this system may be successful. Nevertheless, it is better to use WEP than to not encrypt the network at all.

Some vendors have implemented the non-standard “Dynamic WEP”. It works exactly as WEP and shares the same weaknesses, except that the key is periodically changed by a key management service.

TKIP (defined in WPA/IEEE 802.11i)

This key management protocol defined in the WPA standard uses the same encryption algorithm as WEP, but eliminates its weakness. Because a new key is generated for every data packet, attacks against these keys are fruitless. TKIP is used together with WPA-PSK.

CCMP (defined in IEEE 802.11i)

CCMP describes the key management. Usually, it is used in connection with WPA-EAP, but it can also be used with WPA-PSK. The encryption takes place according to AES and is stronger than the RC4 encryption of the WEP standard.

Configuration with YaST

Security in Wireless Networks

Be sure to use one of the supported authentication and encryption methods to protect your network traffic. Unencrypted WLAN connections allow third parties to intercept all network data. Even a weak encryption (WEP) is better than none at all. Refer to Section “Encryption” and Section “Security” for information.

A WLAN card is usually detected during the installation. In case you need to configure it later, do the following:

Start YaST as user root.

Select Network Devices+Network Settings in the YaST control center. The Network Settings dialog opens. If your network is currently controlled by NetworkManager, it can not be edited by YaST and you see a warning message. Click Ok and the Global Options tab appears. Select Traditional Method with ifup to enable editing with YaST.

Switch to the Overview tab where all network cards that have been detected by the system are listed. If you need more information about general network configuration, refer to Section “Configuring a Network Connection with YaST”.

Choose your wireless card from the list and click Edit to open the Network Card Setup dialog.

Configure whether to use a dynamic or a static IP address under the tab Address. Usually Dynamic Address is fine.

Click Next to proceed to the Wireless Network Card Configuration dialog.

Figure 32.1. YaST: Configuring the Wireless Network Card

Configure operating mode, network name (ESSID), and authentication mode:

Choose the Operating Mode.

A station can be integrated in a WLAN in three different modes. The suitable mode depends on the network in which to communicate: Ad-hoc (peer-to-peer network without access point), Managed (network is managed by an access point), or Master (your network card should be used as the access point). To use any of the WPA-PSK or WPA-EAP modes, the operating mode must be set to Managed.

Select a Network Name (ESSID).

All stations in a wireless network need the same ESSID for communicating with each other. If nothing is specified, the card may automatically selects an access point, which may not be the one you intended to use. Use Scan Network for a list of available wireless networks.

Select an Authentication Mode.

Select a suitable authentication method for your network: No Encryption (not preferable), WEP-Open, WEP-Shared Key, WPA-EAP (WPA version 1 or2), or WPA-PSK (WPA version 1 or2). If you select WPA authentication, a network name (ESSID) must be set. WEP and WPA-PSK authentication methods require to input a key. The key has to be entered as either a Passphrase, as an ASCII string, or Hexadecimal string. You have the following options for your key input type:

WEP Keys

Either enter the default key here or click WEP Keys to enter the advanced key configuration dialog. Set the length of the key to 128 bit or 64 bit. The default setting is 128 bit. In the list area at the bottom of the dialog, up to four different keys can be specified for your station to use for the encryption. Press Set as Default to define one of them as the default key. Unless you change this, YaST uses the first entered key as the default key. If the standard key is deleted, one of the other keys must be marked manually as the default key. Click Edit to modify existing list entries or create new keys. In this case, a pop-up window prompts you to select an input type (Passphrase, ASCII, or Hexadecimal). If you select Passphrase, enter a word or a character string from which a key is generated according to the length previously specified. ASCII requests an input of 5 characters for a 64-bit key and 13 characters for a 128-bit key. For Hexadecimal, enter 10 characters for a 64-bit key or 26 characters for a 128-bit key in hexadecimal notation.

WPA-PSK

To enter a key for WPA-PSK, select the input method Passphrase or Hexadecimal. In the Passphrase mode, the input must be 8 to 63 characters. In the Hexadecimal mode, enter 64 characters.

If you need detailed configuration of your WLAN connection, use the Expert Settings button. Usually there should be no need to change the preconfigured settings. You have the following options:

Channel

The specification of a channel on which the WLAN station should work is only needed in Ad-hoc and Master modes. In Managed mode, the card automatically searches the available channels for access points. In Ad-hoc mode, select one of the offered channels (11 to 14, depending on your country) for the communication of your station with the other stations. In Master mode, determine on which channel your card should offer access point functionality. The default setting for this option is Auto.

Bit Rate

Depending on the performance of your network, you may want to set a certain bit rate for the transmission from one point to another. In the default setting Auto, the system tries to use the highest possible data transmission rate. Some WLAN cards do not support the setting of bit rates.

Access Point

In an environment with several access points, one of them can be preselected by specifying the MAC address.

Use Power Management

When you are on the road, use power saving technologies to maximize the operating time of your battery. Using power management may affect the connection quality and increase the network latency.

Click Next and finish with Ok.

If you have chosen WPA-EAP authentication, another configuration step is needed before your station is ready for deployment in the WLAN.

Enter the credentials you have been given by your network administrator. For TLS, provide Identity, Client Certificate, Client Key, and Server Certificate. TTLS and PEAP require Identity and Password. Server Certificate and Anonymous Identity are optional. YaST searches for any certificate under /etc/cert. Therefore, save the certificates given to you to this location and restrict access to these files to 0600 (owner read and write).

Click Details to enter the advanced authentication dialog for your WPA-EAP setup.

Select the authentication method for the second stage of EAP-TTLS or EAP-PEAP communication. If you selected TTLS in the previous dialog, choose any, MD5, GTC, CHAP, PAP, MSCHAPv1, or MSCHAPv2. If you selected PEAP, choose any, MD5, GTC, or MSCHAPv2. PEAP version can be used to force the use of a certain PEAP implementation if the automatically-determined setting does not work for you.

Establishing an Ad-Hoc Network

In some cases it is useful to connect two computers equipped with a WLAN card. To establish an ad-hoc network with YaST, do the following:

Perform Step 1 to Step 4 as described in Section “Configuration with YaST”.

Choose Statically assigned IP Address and enter the following data:

IP Address: 192.168.1.1. Change this address on the second computer to 192.168.1.2, for example.

Subnet Mask: /24

Hostname: Choose any name you like.

Proceed with Next.

Configure your operating mode, network name (ESSID), and authentication mode:

Choose from the Operating Mode popup menu the entry Ad-hoc.

Choose a Network Name (ESSID). This can be any name, but it has to be used on every computer.

Choose from Authentication Mode the entry No Encryption.

Click Next and finish with Ok.

If you do not have smpppd installed, YaST asks you to do so.

Utilities

The package wireless-tools contains utilities that allow to set wireless LAN specific parameters and get statistics. See http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html for more information.

kismet (package kismet) is a network diagnosis tool with which to listen to the WLAN packet traffic. In this way, you can also detect any intrusion attempts in your network. More information is available at http://www.kismetwireless.net/ and in the manual page.

Tips and Tricks for Setting Up a WLAN

These tips can help tweak speed and stability as well as security aspects of your WLAN.

Stability and Speed

The performance and reliability of a wireless network mainly depend on whether the participating stations receive a clear signal from the other stations. Obstructions like walls greatly weaken the signal. The more the signal strength sinks, the more the transmission slows down. During operation, check the signal strength with the iwconfig utility on the command line (Link Quality field) or with NetworkManager or KNetworkManager. If you have problems with the signal quality, try to set up the devices somewhere else or adjust the position of the antennas of your access points. Auxiliary antennas that substantially improve the reception are available for a number of PCMCIA WLAN cards. The rate specified by the manufacturer, such as 54 Mbit/s, is a nominal value that represents the theoretical maximum. In practice, the maximum data throughout is no more than half this value.

The useful iwspy command can displays WLAN statistics.

iwspy wlan0
wlan0      Statistics collected:
    00:AA:BB:CC:DD:EE : Quality:0  Signal level:0  Noise level:0
    Link/Cell/AP      : Quality:60/94  Signal level:-50 dBm   Noise level:-140 dBm (updated)
    Typical/Reference : Quality:26/94  Signal level:-60 dBm   Noise level:-90 dBm

Security

If you want to set up a wireless network, remember that anybody within the transmission range can easily access it if no security measures are implemented. Therefore, be sure to activate an encryption method. All WLAN cards and access points support WEP encryption. Although this is not entirely safe, it does present an obstacle for a potential attacker. WEP is usually adequate for private use. WPA-PSK would be even better, but it is not implemented in older access points or routers with WLAN functionality. On some devices, WPA can be implemented by means of a firmware update. Furthermore, although Linux supports WPA on most hardware components, some drivers do not offer WPA support. If WPA is not available, WEP is better than no encryption. In enterprises with advanced security requirements, wireless networks should only be operated with WPA.

Troubleshooting

If your WLAN card is not automatically detected, check whether it is supported by openSUSE. A list of supported WLAN network cards is available under http://en.opensuse.org/HCL/Network_Adapters_(Wireless). If your card is not supported, it may be possible to make it work using the Microsoft Windows drivers with Ndiswrapper. Please refer to http://en.opensuse.org/Ndiswrapper for detailed information.

If your WLAN card fails to respond, check if you have downloaded the needed firmware. Refer to /usr/share/doc/packages/wireless-tools/README.firmware for more information.

Multiple Network Devices

Modern laptops usually have a network card and a WLAN card. If you configured both devices with DHCP (automatic address assignment), you may encounter problems with the name resolution and the default gateway. This is evident from the fact that you can ping the router but cannot surf the Internet. The Support Database features an article on this subject at http://en.opensuse.org/SDB:Name_Resolution_Does_Not_Work_with_Several_Concurrent_DHCP_Clients.

Problems with Prism2 Cards

Several drivers are available for devices with Prism2 chips. The various cards work more or less smoothly with the various drivers. With these cards, WPA is only possible with the hostap driver. If such a card does not work properly or not at all or you want to use WPA, read /usr/share/doc/packages/wireless-tools/README.prism2.

For More Information

More information can be found on the following pages:

http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Wireless.html—The Internet pages of Jean Tourrilhes, who developed the Wireless Tools for Linux, present a wealth of useful information about wireless networks.

tuxmobil.org—Useful hands-on information about mobile computers under Linux .

http://www.linux-on-laptops.com—More information about Linux on laptops.

Chapter 33. Using Tablet PCs

Abstract

openSUSE® comes with support for Tablet PCs. In the following, learn how to install and configure your Tablet PC and discover some useful Linux* applications which accept input from digital pens.

The following Tablet PCs are supported:

Tablet PCs with serial Wacom devices, such as ACER TM C30x series, Fujitsu Lifebook T series (T30xx/T40xx/T50xx), Gateway C-140X/E-295C, HP Compaq TC1100/TC4200/TC4400, 2710p/2730p , IBM/Lenovo X41t/X61t, LG LT20, Motion M1200/M1400, OQO 02, Panasonic Toughbook CF-18, Toshiba Portege/Tecra M series, Satellite R15/R20.

Tablet PCs with Wacom USB devices, such as ASUS R1E/R1F, Gateway C-120X/E-155C, HP Pavilion tx2000/tx2100/tx2500 series.

Tablet PCs with FinePoint devices, such as Gateway C210X/M280E/CX2724, HP Compaq TC1000.

Tablet PCs with touch screen devices, such as Asus R2H, Clevo TN120R, Fujitsu Siemens Computers P-Series, LG C1, Samsung Q1/Q1-Ultra.

After you have installed the Tablet PC packages and configured your digitizer correctly, input with the pen (also called a stylus) can be used for the following actions and applications:

Logging in to KDM or GDM

Unlocking your screen on the KDE and GNOME desktops

Actions that can also be triggered by other pointing devices (such as mouse or touch pad), for example, moving the cursor on the screen, starting applications, closing, resizing and moving windows, shifting window focus and dragging and dropping objects

Using gesture recognition in applications of the X Window System

Drawing with GIMP

Taking notes or sketching with applications like Jarnal or Xournal or editing larger amounts of text with Dasher

Keyboard or Mouse Needed for Installation

During installation of openSUSE, the pen cannot be used as an input device. If your Tablet PC does not feature a built-in keyboard or touch pad, connect an external keyboard or mouse to your Tablet PC for installation of your system.

Installing Tablet PC Packages

The packages needed for Tablet PCs are included in the TabletPC installation pattern—if this is selected during installation, the following packages should already be installed on your system:

cellwriter: a character-based hardwriting input panel

jarnal: a Java-based note taking application

wacom-kmp(-default): the kernel driver for Tablet PCs with USB Wacom devices

xournal: an application for note taking and sketching

xstroke: a gesture recognition program for the X Window System

xvkbd: a virtual keyboard for the X Window System

x11-input-fujitsu: the X input module for Fujitsu P-Series tablets

x11-input-evtouch: the X input module for some Tablet PCs with touch screens

x11-input-wacom: the X input module for Wacom tablets

x11-input-wacom-tools: configuration, diagnostics, and libraries for Wacom tablets

If these packages are not installed, manually install the packages you need from command line or select the TabletPC pattern for installation in YaST.

Configuring Your Tablet Device

You can configure your Tablet PC (this does not include Tablet PCs with touch screens) during the installation process in the Hardware Configuration screen by changing the Graphics Card options. Alternatively you can configure the (internal or external) tablet device at any time after the installation.

Start SaX2 from the command line or by pressing Alt+F2 and entering sax2.

If you use a Wacom or Finepoint device, click Tablet to show the Tablet Properties.

If you use a Tablet PC with a touch screen, click Touchscreen instead.

From the list on the right, select TABLET PCs as vendor, and the name of your tablet and check Activate This Tablet.

If your machine is not listed and you are sure that you have a Wacom device, select either Wacom ISDV4 Tablet PC (SERIAL) or Wacom ISDV4 Tablet PC (USB).

Switch to the Electronic Pens tab and make sure the following options are activated: Add Pen and Add Eraser. If you have a Tablet PC with touch screen, also activate Add Touch.

Click OK to save the changes.

After finishing the X Window System configuration, restart your X server by logging out. Alternatively, leave the user interface and run init 3 && init 5 in a virtual console.

After your tablet device has been configured, you can now make use of your pen (or, depending on your Tablet PC, your finger) as input device.

Using the Virtual Keyboard

To log in to the KDE or GNOME desktop or to unlock the screen, you can either enter your username and password as usual or via the virtual keyboard (xvkbd) displayed below the login field. To configure the keyboard or to access the integrated help, click the xvkbd field at the left lower corner and open the xvkbd main menu.

If your input is not visible (or is not transferred to the window where you need it), redirect the focus by clicking the Focus key in xvkbd and then clicking into the window that should get the keyboard events.

Figure 33.1. xvkbd Virtual Keyboard

If you want to use xvkbd after login, start it from the main menu or with xvkbd from a shell.

Rotating Your Display

Use KRandRTray (KDE) or gnome-display-properties (GNOME) to rotate or resize your display manually on the fly. Both KRandRTray and gnome-display-properties are applets for the RANDR extension of the X server.

Start KRandRTray or gnome-display-properties from the main menu, or enter krandrtray or gnome-display-properties to start the applet from a shell. After you have started the applet, the applet icon is usually added to your system tray. If the gnome-display-properties icon does not automatically appear in the system tray, make sure Show Displays in Panel is activated in the Monitor Resolution Settings dialog.

To rotate your display with KRandRTray, right-click the icon and select Configure Display. Select the desired orientation from the configuration dialog.

To rotate your display with gnome-display-properties, right-click the icon and select the desired orientation. Your display is immediately tilted to the new direction. The orientation of the graphics tablet changes also, so it can still interpret the movement of the pen correctly.

If you have problems changing the orientation of your desktop, refer to Section “Troubleshooting” for more information.

For more information about the desktop-specific applets for the RANDR extension refer to “Monitor Settings” (Chapter “Customizing Your Settings”, ↑KDE User Guide) and “Configuring Screens” (Chapter “Customizing Your Settings”, ↑GNOME User Guide).

Using Gesture Recognition

openSUSE includes both CellWriter and xstroke for gesture recognition. Both applications accept gestures executed with the pen or other pointing devices as input for applications on the X Window System.

Using CellWriter

With CellWriter, you can write characters into a grid of cells—the writing is instantly recognized on a character basis. After you have finished writing, you can send the input to the currently focused application. Before you can use CellWriter for gesture recognition, the application needs to be trained to recognize your handwriting: You need to train each character of a certain map of keys (untrained characters are not activated and thus cannot be used).

Procedure 33.1. Training CellWriter

Start CellWriter from the main menu or with cellwriter from the command line. On the first start, CellWriter automatically starts in the training mode. In training mode it shows a set of characters of the currently chosen key map.

Enter the gesture you would like to use for a character into the respective character's cell. With the first input, the background changes its color to white, whereas the character itself is shown in light grey. Repeat the gesture multiple times until the character changes its color to black. Untrained characters are shown on a light grey or brown background (depending on the desktop's color scheme).

Repeat this step until you have trained CellWriter for all characters you need.

If you want to train CellWriter for another language, click the Setup button and select a language from the Languages tab. Close the configuration dialog. Click the Train button and select the key map from the drop-down box at the bottom right corner of the CellWriter window. Now repeat your training for the new map of keys.

After having finished the training for the map of keys, click the Train button to switch to the normal mode.

In the normal mode, the CellWriter windows shows a couple of empty cells in which to enter the gestures. The characters are not sent to another application until you click the Enter button, so you can correct or delete characters before you use them as input. Characters that have been recognized with a low degree of confidence will appear highlighted. To correct your input, use the context menu that appears on right-clicking a cell. To delete a character, either use your pen's eraser, or middle-click with the mouse to clear the cell. After finishing your input in CellWriter, define which application should receive the input by clicking into the application's window. Then send the input to the application by clicking Enter.

Figure 33.2. Gesture Recognition with CellWriter

If you click the Keys button in CellWriter, you get a virtual keyboard that can be used instead of the handwriting recognition.

To hide CellWriter, close the CellWriter window. The application now appears as icon in your system tray. To show the input window again, click the icon in the system tray.

Using Xstroke

With xstroke, you can use gestures with your pen or other pointing devices as input for applications on the X Window System. The xstroke alphabet is a unistroke alphabet that resembles the Graffiti* alphabet. When activated, xstroke sends the input to the currently focused window.

Start xstroke from the main menu or with xstroke from a shell. This adds a pencil icon to your system tray.

Start the application for which you want to create text input with the pen (for example, a terminal window, a text editor or an OpenOffice.org Writer).

To activate the gesture recognition mode, click the pencil icon once.

Perform some gestures on the graphics tablet with the pen or another pointing device. xstroke captures the gestures and transfers them to text that appears in the application window that has the focus.

To switch focus to a different window, click the desired window with the pen and hold for a moment (or use the keyboard shortcut defined in your desktop's control center).

To deactivate the gesture recognition mode, click the pencil icon again.

Taking Notes and Sketching with the Pen

To create drawings with the pen, you can use a professional graphics editor like GIMP or try one of the note-taking applications, Xournal or Jarnal. With both Xournal and Jarnal, you can take notes, create drawings or comment PDF files with the pen. As a Java-based application available for several platforms, Jarnal also offers basic collaboration features. For more information, refer to http://www.dklevine.com/general/software/tc1000/jarnal-net.htm. When saving your contents, Jarnal stores the data in an archive format (*.jaj) that also contains a file in SVG format.

Start Jarnal or Xournal from the main menu or by entering jarnal or xournal in a shell. To comment a PDF file in Xournal, for example, select File+Annotate PDF and open the PDF file from your file system. Use the pen or another pointing device to annotate the PDF and save your changes with File+Print to PDF.

Figure 33.3. Annotating a PDF with Xournal

Dasher is another useful application. It was designed for situations where keyboard input is impractical or unavailable. With a bit of training, you can rapidly enter larger amounts of text using only the pen (or other input devices—it can even be driven with an eye tracker).

Start Dasher from the main menu or with dasher from a shell. Move your pen in one direction and the application starts to zoom into the letters on the right side. From the letters passing the cross hairs in the middle, the text is created or predicted and is printed to the upper part of the window. To stop or start writing, click the display once with the pen. Modify the zooming speed at the bottom of the window.

Figure 33.4. Editing Texts with Dasher

The Dasher concept works for many languages. For more information, refer to the Dasher Web site, which offers comprehensive documentation, demonstrations and training texts. Find it at http://www.inference.phy.cam.ac.uk/dasher/

Troubleshooting

Virtual Keyboard Does Not Appear on Login Screen

Occasionally, the virtual keyboard is not displayed on the login screen. To solve this, restart the X server by pressing Ctrl+Alt+<— or press the appropriate key on your Tablet PC (if you use a slate model without integrated keyboard). If the virtual keyboard still does not show, connect an external keyboard to your slate model and log in using the hardware keyboard.

Orientation of the Wacom Graphics Tablets Does Not Change

With the xrandr command, you can change the orientation of your display from within a shell. Enter xrandr --help to view the options available. To simultaneously change the orientation of your graphics tablet, the command needs to be modified as described below:

For normal orientation (0° rotation):

xrandr --output LVDS ---rotate normal && xsetwacom set "Mouse[7]" Rotate NONE

For 90° rotation (clockwise, portrait):

xrandr --output LVDS ---rotate right && xsetwacom set "Mouse[7]" Rotate CW

For 180° rotation (landscape):

 xrandr --output LVDS --rotate inverted && xsetwacom set "Mouse[7]" Rotate HALF

For 270° rotation (counterclockwise, portrait):

 xrandr --output LVDS --rotate left && xsetwacom set "Mouse[7]" Rotate CCW

Note that the commands above depend on the contents of your /etc/X11/xorg.conf configuration file. If you have configured your device with SaX2 as described in Section “Configuring Your Tablet Device”, the commands should work as they are written. If you have changed the Identifier of the tablet stylus input device in xorg.conf manually, replace "Mouse[7]" with the new Identifier. If you have a Wacom device with Touch support (you can use your fingers on the tablet to move the cursor), you need to rotate also the touch device.

For More Information

Some of the applications mentioned here do not offer integrated online help, but you can find some useful information about usage and configuration in your installed system in /usr/share/doc/package/packagename or on the Web:

For the Xournal manual, refer to http://xournal.sourceforge.net/manual.html

The Jarnal documentation is located at http://www.dklevine.com/general/software/tc1000/jarnal.htm#documentation

Find the xstroke man page at http://davesource.com/Projects/xstroke/xstroke.txt

Find a HOWTO for configuring X on the Linux Wacom Web site: http://linuxwacom.sourceforge.net/index.php/howto/x11

Find a very informative Web site about the Dasher project at http://www.inference.phy.cam.ac.uk/dasher/

Find more information and documentation about CellWriter at http://risujin.org/cellwriter/

Information on gnome-display-properties can be found at http://en.opensuse.org/GNOME/Multiscreen

Chapter 34. Copying and Sharing Files

Abstract

If using multiple operating systems (OS) simultaneously, it is often necessary to exchange files among them. Different systems may reside on different partitions on the same machine or on different machines across your network. There are various approaches to file exchange with different basic instructions and possible pitfalls.

Scenarios for Private Home Networks Only

Do not use the following scenarios in networks other than your own private and trusted home network that is protected by a firewall. Implementing high security measures for the configurations featured in the following sections is beyond the scope of this document.

Exchanging data may encompass either one of the following tasks:

Copying

To copy your data means to transfer your data from one system to the other. This results in identical objects on both the source and the target system.

Synchronizing data is a special way to copy data. If you change a file on one computer, it is automatically changed on the other computer after the synchronization. For example, think of a laptop that contains your modified files and you want to have the same contents on your desktop computer.

Sharing

Sharing your files means establishing a client/server relationship. The server provides files that can be accessed by the client. When changing a file, you modify it on the server, not locally on the client. File servers typically serve a large number of clients simultaneously.

Scenarios

The following list provides a number of possible scenarios involving file transfer:

Different OS on the Same Computer

Many users have an operating system preinstalled by their vendor and run Linux in a separate partition. Refer to Section “Accessing Files on Different OS on the Same Computer” for more information.

Different Computers Not Connected by a Network

Save the data to any media (CD, DVD, USB flash drive, or external hard disk) and connect these to the target machine to copy your files. This solution is inexpensive, intuitive, and straightforward. However, you need the appropriate drives or ports on both computers. Media are suited to occasional file transfers with limited file size. If you need a more permanent solution, consider connecting them with a network.

Different Computers Connected to the Same Network

Set up a server of any kind on one computer, connect the server and the client, and transfer the files from server to client. Choose from various protocols available and pick the one that best matches your needs and expertise.

The client/server setup requires more expertise and maintenance efforts, but is better suited to routine transfer needs and exchange with multiple systems. If you are looking for a permanent file exchange, choose a client/server-based method. This method does not impose any limits on the amount of data that can be transferred. See Section “Access Methods”.

Different Computers on Different Networks

This scenario requires connection of different networks and is beyond the scope of this document. Transfer files as if the computers were not connected to a network.

Access Methods

The following methods and protocols are well-suited to file transfer and sharing.

FTP

Use FTP (File Transfer Protocol) if you need to exchange files very often and with different users. Set up an FTP server on one system and access it with clients. There are many graphical client applications available for FTP on Windows*, MacOS, and Linux. Depending on how your FTP server is used, enable read and write permissions. See Section “Copying Files with FTP” for more details on FTP.

NFS

NFS (Network File System) is a client/server system. A server exports one or more directories that can be imported by a client. For more information, see Chapter 26, Sharing File Systems with NFS.

Use NFS if you share files very often and for different users. Generally, this protocol is more common in the Linux world than in the Windows world. An NFS export integrates well into your Linux system and you can browse the imported directory structure like any other folder on your local machine. Depending on your configuration, enable either read or write permissions or both on the server. In general, for a home user it makes sense to allow read and write access.

rsync

Use rsync to transfer regularly large volumes of data that does not change considerably. It is available on Linux and Windows. A typical use case for rsync is managing data backups. Refer to the manual page of the rsync command and Section “Transferring Files with rsync” for more information.

Unison

Unison is an alternative to rsync. It is used to regularly synchronize files between different computers but has the advantage to behave bidirectionally. Refer to the manual page of the Unison command and Section “Transferring Files with Unison” for more information. Unison is available on Linux and Windows.

SMB

Samba is a client/server system and an implementation of the SMB protocol. It is usually used in Windows networks, but is supported by several operating systems. Refer to Chapter 27, Samba for more information about Samba.

Use Samba if you need to share files very often and with different users, especially to Windows systems. Samba as a Linux-only solution is uncommon, use NFS instead. For more information about setting up a Samba server, refer to Section “Sharing Files between Linux and Windows with Samba”.

SSH

SSH (Secure Shell) enables a secure connection between computer. The SSH suite consists of several commands and uses public key encryption to authenticate users. For more information, see “SSH: Secure Network Operations” (↑Security Guide).

Use SSH if you copy files occasionally over an untrusted network and if you are the only user doing so. Although there are graphical user interfaces available, SSH is mainly considered a command line utility and is available on Linux and Windows.

Accessing Files Using a Direct Connection

This section describes one way to exchange files between two computers using an Ethernet crossover cable.

You need:

Ethernet crossover cable. For further information see: http://en.wikipedia.org/wiki/Ethernet_crossover_cable

openSUSE on both computers

An established connection. See “General Notes on File Sharing and Network Browsing” (Chapter “Accessing Network Resources”, ↑KDE User Guide).

Proceed as follows:

Procedure 34.1. GNOME

Start Nautilus.

Click on File+Connect to Server.

Set the Service Type to ssh.

Enter the IP address and port of the remote computer (default: 22).

Specify the folder you want to open on the remote Computer.

Click Connect.

Procedure 34.2. KDE

Start Dolphin.

Click on Network, Add Network. Re-attach the pane if it is not available with View+Panels+Places.

Set the type of network to Secure shell (ssh).

Enter any name and the correct user, IP address, port (default: 22) and folder of the remote Computer. It is also possible to create an icon for this connection by enabling the checkbox below. This connection icon appears in the Network tab in Dolphin.

Click on Save & Connect a dialog box opens and requests the password.

A new window containing the files of the remote computer will be opened.

Accessing Files on Different OS on the Same Computer

New computers generally ship with a preinstalled operating system, usually Windows. If you have installed Linux on a different partition, you might want to exchange files between the different operating systems.

Windows can not read Linux partitions by default. If you want to exchange files between these two operating systems, you have to create an “exchange partition”. If you prefer a more direct approach, look at http://www.fs-driver.org/ to get a driver supporting an ext2 filesystem on Windows. The following file systems are used by Windows and can be accessed from a Linux machine:

FAT

Various flavors of this file system are used by MS-DOS and Windows 95 and 98. You can create this type of file system with YaST. It is possible to read and write files on FAT partitions from Linux. The size of a FAT partition (and even the maximum size of a single file) is subject to restrictions, depending on the FAT version. See http://en.wikipedia.org/wiki/VFAT for more information about FAT file systems.

NTFS

The NTFS file system is used by Windows NT, Windows 2000, Windows XP, Windows Server 2003 and Windows Vista. openSUSE includes write access support to the NTFS file system. However, the driver for the NTFS-3g filesystem has limited functionality. At the moment there is no support for Windows file permissions and you can not access encoded or compressed files. See http://en.opensuse.org/NTFS-3g for more information about NTFS-3g.

During the installation of openSUSE, your Windows partitions are detected. After starting your Linux system, the Windows partitions usually are mounted. These are possible ways of accessing your Windows data:

KDE

Press Alt+F2 and enter sysinfo:/. A new window opens displaying the characteristics of your machine. Disk Information lists your partitions. Look at those that are of the file system type ntfs or vfat and click on these entries. If the partition is not already mounted, KDE mounts the partition now and displays the contents.

Command Line

Just list the contents of /windows to see one or more directories containing your Windows drives. The directory /windows/c maps to the Windows drive C:\, for example.

Changing the Accessibility of Windows Partitions

Initially, Windows partitions are mounted read-only for normal users to avoid accidental damage to the file system. To grant normal users full access to a mounted Windows partition, change the mount behavior of this Windows partition. Refer to the manual page of the mount command for more information on mount options for vfat and to the maual page of ntfs-3g on mount options for NTFS.

Copying Files between Linux Computers

Linux offers a rich set of protocols you can use to copy files between computers. Which protocol you use depends on how much effort you want to invest and whether you need to be compatible with future Windows installations. The following sections feature various methods to transfer files from and to Linux computers. Make sure that you have a working network connection, because otherwise they will not work. All scenarios rely on working name resolution in the network. If your network does not include a name service, use IP addresses directly or add the IP addresses along with respective hostnames to /etc/hosts on all clients.

The following example IP addresses and hostnames are used across this section:

Target Hostname

jupiter.example.com

Target IP

192.168.2.100

Source Hostname

venus.example.com

Source IP

192.168.2.101

User

tux

Copying Files with SSH

The following requirements must be met on both computers that are accessed via SSH:

If you use a hostname, make sure each hostname is listed in /etc/hosts on both computers (see Section “/etc/hosts”.) If you use SSH with IP addresses, you do not need to change anything.

If you use a firewall, open the SSH port. To do so, start YaST, and select Security and Users+Firewall. Go to Allowed Services and check whether SSH is displayed as part of the list. If this is not the case, select SSH from Service to Allow and click Add. Apply your changes and leave YaST with Next and Finish.

To copy files from one computer to another, you need to know where the files are located. For example, to copy the single file /srv/foo_file from computer jupiter.example.com to the current directory, use the following scp command (the dot represents the current directory as the copy target location):

scp tux@jupiter.example.com:/srv/foo_file .

To copy a whole directory structure, use the recursive mode of scp:

scp -r tux@jupiter.example.com:/srv/foo_directory .

If your network does not provide name resolution, use the server's IP address directly:

scp tux@192.168.2.100:/srv/foo_file .

If you do not know exactly where your files are, use the sftp command. Copying files in KDE or GNOME with SFTP is very simple. Proceed as follows:

Press Alt+F2.

Enter the following at the address prompt (correct it to your own values):

sftp://tux@jupiter.example.com

Confirm the question regarding of authenticity and enter the password of tux on jupiter.example.com.

Drag and drop the desired files or directories to your desktop or a local directory.

KDE provides another protocol called fish that can be used if sftp is not available. The use of this protocol is similar to sftp. Just replace the sftp protocol prefix of the URL with fish:

fish://tux@jupiter.example.com

Transferring Files with rsync

rsync is useful for archiving or copying data and can also be used as a daemon to provide directories to the network (see Procedure 34.3, “Advanced Setup for rsync Synchronization”).

Before using rsync to synchronize files and directories between different computers, make sure that the following requirements are met:

The package rsync is installed.

Identical users are available on both systems.

Enough disk space is available on the server.

If you want to benefit from rsync's full potential, make sure that rsyncd is installed on the system to use as the server.

rsync Basic Mode

The basic mode of operation of rsync does not require any special configuration. rsync mirrors complete directories onto another system. Its usage is not much different from a regular copying tool, such as scp. The following command creates a backup of the home directory of tux on a backup server called jupiter:

rsync -Hbaz -e ssh /home/tux/ tux@jupiter:backup

Use the following command to restore your backup (without option -b):

rsync -Haz -e ssh tux@jupiter:backup /home/tux/

rsync Daemon Mode

Start the rsyncd daemon on one of your systems to make use of the full functionality of rsync. In this mode, it is possible to create synchronization points (modules) that can be accessed without an account. To use the rsyncd daemon, proceed as follows:

Procedure 34.3. Advanced Setup for rsync Synchronization

Log in as root and install the rsync package.

Configure your synchronization points in /etc/rsyncd.conf. Add a point with its name in brackets and add the path keyword like in the following example:

[FTP]
  path = /srv/ftp
 comment = An Example

Start the rsyncd daemon as root with rcrsyncd start. To start the rsync service automatically during each system boot, run insserv rsyncd.

List all files located in the /srv/ftp directory (note the double colon):

rsync -avz jupiter::FTP

Initiate the transfer by providing a target directory (in this example, the current directory is represented by a dot):

rsync -avz jupiter::FTP .

By default, files are not deleted while synchronizing with rsync. To force file deletion, add the --delete option. To make sure that --delete does not accidentally remove newer files, use the --update option instead. Any conflicts that arise must be resolved manually.

Transferring Files with Unison

Before using Unison to synchronize files and directories between different computers, make sure that the following requirements are met:

The package unison is installed.

Enough disk space is available on your local and remote computer.

If you want to benefit from Unison's full potential, make sure that Unison is also installed and running on the remote computer.

In case you need help, run Unison with the -doc topics option to get a full list of available sections.

For permanent settings, Unison allows the creation of profiles that specify Unison preferences such as the directories (roots) to synchronize, which types of files to ignore, and other options. The profiles are stored as text files in ~/.unison with the file extension *.prf.

Using the GUI

To synchronize different directories with Unison's GUI, proceed as follows:

Start Unison by pressing Alt+F2 and entering unison.

If you run Unison for the first time and without any further options, you are prompted for a source directory. Enter the source directory you want to synchronize and click OK.

Enter the target directory. It can be either local or remote. If you want to synchronize to a remote directory, choose the method (SSH, RSH or Socket) and enter the hostname and an optional user.

If you have not synchronized these two directories before, a warning dialog appears, informing you that Unison will now compare the contents of those directories. Close the warning with OK and wait until Unison has collected the information from both directories and displays the differences in the main window.

The left column shows the source directory you have selected, the third column shows the target directory. If there are differences between the directories, the Action column shows a symbol, proposing an action. A green arrow indicates that a file has been modified, added or deleted in the source or the target directory. The direction of the arrow indicates the direction that the change would be propagated if you performed the synchronization now. A question mark indicates a conflict (both files have been changed and Unison cannot decide which one to overwrite).

Figure 34.1. File Synchronization Proposal

To modify the proposals Unison shows for each file (for example, if you want to change the direction), select the file and click Right to Left or Left to Right. With Skip, exclude a file from synchronization. The symbol in the Action column changes accordingly.

To start the synchronization, click Go.

The next time you start Unison, a dialog box shows the existing profiles, each specifying a pair of directories to be synchronized. Select a profile or create a new profile (for another pair of directories) and perform the synchronization as described above.

Using the Command Line

Unison can also be operated through the command line. To synchronize a local directory to a remote computer, proceed as follows:

Open a shell and enter the following command:

unison -ui text DIR
         ssh://tux@jupiter.example.com//PATH

Replace the placeholders with the respective values.

Unison asks you what to do with your files and directories, for example:

local                  jupiter
           <----  new file   dir [f]

Press F if you want to follow Unison's recommendation. For other commands, press ?.

Proceed with y, if you want to propagate your updates.

Copying Files with FTP

Before configuring your FTP server, make sure that the following requirements are met:

The package vsftp is installed.

You have root access to your FTP server.

Enough disk space is available on your computer.

For Home Networks Only

This setup is suited for use in home networks only. Do not deploy it to sites unprotected by firewalls and do not enable world wide access.

To configure an FTP server, proceed as follows:

Prepare the FTP server:

Open a shell, log in as root, and save a backup copy of /etc/vsftpd.conf:

cp /etc/vsftpd.conf /etc/vsftpd.conf.bak

Create an access point for anonymous FTP

mkdir ~ftp/incoming
chown -R ftp:ftp ~ftp/incoming

Replace the configuration files according to the preferred scenario (refer to the manual page of vsftpd.conf for advanced configuration options):

Allowing Anonymous Read and Write Access

#
listen=YES

# Enable anonymous access to FTP server
anonymous_enable=YES

#
local_enable=YES
# Enable write access
write_enable=YES
anon_upload_enable=YES
anon_mkdir_write_enable=YES
dirmessage_enable=YES
# Write log file
xferlog_enable=YES
connect_from_port_20=YES
chown_uploads=YES
chown_username=ftp
ftpd_banner=Welcome to FTP service.
anon_root=/srv/ftp

Grant Restricted Permissions to FTP Users (Home Only)

chroot_local_users=YES

Restart the FTP server:

rcvsftp start

On the client, just enter the URL ftp://HOST in your browser or FTP client. Replace HOST with the hostname or IP address of your server. There are many graphical user interfaces available that are suited to browsing the contents of your FTP server. For a list of them, just enter FTP at the search prompt of the YaST package manager.

Copying Files between Linux and Windows Computers with SSH

To transfer files from Linux to Windows using SSH, choose one of the following applications:

PuTTY

PuTTY is a suite of different command line tools for working with an SSH daemon. Download it from http://www.chiark.greenend.org.uk/~sgtatham/putty.html.

WinSCP

WinSCP is very similar to PuTTY, but includes a graphical user interface. Choose from an Explorer or Norton Commander style. Download it from http://winscp.net.

To copy a file from Windows to Linux with PuTTY, proceed as follows (on the Windows machine):

Start PSCP.

Enter the hostname of your SSH server.

Enter your login and password to the SSH server.

To connect from Windows to Linux with WinSCP, proceed as follows (on the Windows machine):

Start WinSCP.

Enter the hostname of the SSH server and username.

Click Login and acknowledge the resulting warning.

Drag and drop any files or directories from or to your WinSCP window.

SSH Fingerprint

With both PuTTY and WinSCP, you must accept the SSH fingerprint when you log in for the first time.

Sharing Files between Linux Computers

The following sections feature various methods for sharing data. Use one of these if you are looking for a permanent solution for data sharing.

Transferring Files with NFS

To configure the server, proceed as follows:

Prepare the system:

Open a shell, log in as root, and grant write permissions to all users:

mkdir /srv/nfs
chgrp users /srv/nfs
chmod g+w /srv/nfs

Make sure that your user name and user ID is known on the client as well as on the server. Refer to Chapter 8, Managing Users with YaST for detailed instructions about how to create and manage user accounts.

Prepare the NFS server:

Start YaST as root.

Select Network Services+NFS Server (this module is not installed by default. If it is missing in YaST, install the package yast2-nfs-server).

Enable NFS services with Start.

Open the appropriate firewall port with Open Port in Firewall if you are using a firewall.

Export the directories:

Click Add directory and select /srv/nfs.

Set the export options to:

rw,root_squash,async

Repeat these steps, if you need to export more than one directory.

Apply your settings and leave YaST. Your NFS server is ready to use.

To manually start the NFS server, enter rcnfsserver start as root. To stop the server, enter rcnfsserver stop. By default, YaST takes care of starting this service at boot time.

To configure the client, proceed as follows:

Prepare the NFS client:

Start YaST as root.

Select Network Services+NFS Client.

Activate Open Port in Firewall if using a firewall.

Import the remote file system:

Click Add.

Enter the name or IP address of the NFS server or click Choose to automatically scan the network for NFS servers.

Enter the name of your remote file system or automatically choose it with Select.

Enter an appropriate mount point, for example /mnt.

Repeat these steps if you need to import more than one external directory.

Apply your settings and leave YaST. Your NFS client is ready to use.

To start the NFS client manually, enter rcnfs start.

Consistent User Names

If your home network is used by just a small number of users, set up identical users manually on all machines. If, however, you need a larger consistent user base across a larger home network, consider using NIS or LDAP to manage user data. For further information, refer to “Using NIS” (↑Security Guide) and “LDAP—A Directory Service” (↑Security Guide).

Sharing Files with Samba

This sections introduces various methods to access files on a Samba server. Both KDE and GNOME ship with graphical tools for working with Samba shares. There is also a command line tool for accessing Samba servers.

Accessing Shares with KDE and GNOME

Both the KDE and GNOME desktops can access Samba shares through their file browsers. To access your share, proceed as follows:

Press Alt+F2 and enter smb://jupiter.example.com/share.

The syntax of this URL is smb://HOST/SHARENAME with HOST representing the hostname (jupiter.example.com) or IP address and SHARENAME representing the share. See Step 3.b.

Log in with the username and password. The password is set in Step 4 or just hit Enter if no password is needed.

Drag and drop any files or directories from or to your window.

If you do not know your workgroup, enter smb:/ to list all workgroups available in your network. The Smb4K tool (package smb4k) can also be used to display all workgroups in your network and mount them on demand.

Accessing Shares from the Command Line

If you prefer using the command line, use the smbclient command. To log in to your Samba server, run:

smbclient //jupiter/share -U tux

Omit the -U option if you are the current user tux. After logging in successfully, use some basic commands like ls (list contents), mkdir (create directory), get (download file), and put (upload file). Use help to display all commands. Refer to the manual page of smbclient for more information.

Sharing Files between Linux and Windows with Samba

Samba is the first choice for transferring files between Windows and Linux machines. These are the most common use cases for Samba:

Transferring Files from Linux to Windows with the SMB Scheme

In the easiest case you do not have to configure a Linux server. Use the smb:/ scheme. For more information, see Section “Accessing Shares with KDE and GNOME”. Make sure that your workgroup is identical on both systems and that your directories are shared.

Transferring Files from Windows to Linux Using a Server

Configure a Samba server on your Linux computer. See Procedure 34.4, “Setting Up a Samba Server”.

Using Default Registry Entries for Your Windows System

Some Windows versions (95, 98) require a small change in the registry for enabling a different password authentication method. Simplify this step by installing the samba-doc package and copy the file /usr/share/doc/packages/samba/registry to your Windows drive. Start Windows and incorporate the changes by double-clicking on this file.

Procedure 34.4. Setting Up a Samba Server

To set up a Samba server, do the following:

Prepare the Samba server:

Start YaST as root.

Install the samba package.

Create a directory (for example, /srv/share).

Create the server configuration:

Select Network Services+Samba Server.

Select one of the workgroups or enter a new one (for example, Penguin).

Check Primary Domain Controller (PDC)

Set During Boot if the Samba service should be started every time your computer boots. Otherwise set Manually.

Activate Open Port in Firewall if you use a firewall.

Create your Windows share:

Change to the Shares tab and click Add.

Enter a name and description. The Share Name is used for accessing the share from your clients. Share Description describes the purpose of the share.

Select your path (for example, /src/share).

Proceed with OK.

Activate Allow Users to Share Their Directories.

Provide a password for all users that are allowed to use this service:

smbpasswd -a tux

For easier configuration, just hit Enter to leave the password empty. Take into account that the usernames on your Windows and Linux computers are probably different. Configuring a consistent user base for both Windows and Linux is beyond the scope of this document.

Start the Samba server:

rcnmb start
rcsmb start

To check if everything has been successfully configured, enter:

smbclient -L localhost

After you hit Enter, you should get something like the following:

Anonymous login successful
Domain=[PENGUIN] OS=[Unix] Server=[Samba 3.0.22-11-SUSE-CODE10]

    Sharename       Type      Comment
    ---------       ----      -------
    share           Disk      Shared directory
    netlogon        Disk      Network Logon Service
    IPC$            IPC       IPC Service (Samba 3.0.22-11-SUSE-CODE10)
    ADMIN$          IPC       IPC Service (Samba 3.0.22-11-SUSE-CODE10)
Anonymous login successful
Domain=[PENGUIN] OS=[Unix] Server=[Samba 3.0.22-11-SUSE-CODE10]

    Server               Comment
    ---------            -------
    SUSE-DESKTOP         Samba 3.0.22-11-SUSE-CODE10

    Workgroup            Master
    ---------            -------
    TUX-NET              jupiter

For More Information

http://en.wikipedia.org/wiki/VFAT

http://en.wikipedia.org/wiki/NTFS

http://en.wikipedia.org/wiki/Fstab

http://en.wikipedia.org/wiki/Network_File_System

http://en.wikipedia.org/wiki/File_Transfer_Protocol

http://en.wikipedia.org/wiki/SSH

http://en.wikipedia.org/wiki/Rsync

http://en.wikipedia.org/wiki/Samba_software

Chapter 35. Help and Documentation

Abstract

openSUSE® comes with various sources of information and documentation, many of which are already integrated into your installed system:

Documentation in /usr/share/doc

This traditional help directory holds various documentation files and release notes for your system. Find more detailed information in Section “Documentation Directory”.

Man Pages and Info Pages for Shell Commands

When working with the shell, you do not need to know the options of the commands by heart. Traditionally, the shell provides integrated help by means of man pages and info pages. Read more in Section “Man Pages” and Section “Info Pages”.

Desktop Help Centers

The help centers of both the KDE desktop (KDE help center) and the GNOME desktop (Yelp) provide central access to the most important documentation resources on your system in searchable form. These resources include online help for installed applications, man pages, info pages, and the Novell/SUSE manuals delivered with your product.

Separate Help Packages for Some Applications

When installing new software with YaST, the software documentation is installed automatically (in most cases) and usually appears in the help center of your desktop. However, some applications, such as GIMP, may have different online help packages that can be installed separately with YaST and do not integrate into the help centers.

Documentation Directory

The traditional directory to find documentation on your installed Linux system is /usr/share/doc. Usually, the directory contains information about the packages installed on your system, plus release notes, manuals, and more.

Contents Depends on Installed Packages

In the Linux world, many manuals and other kinds of documentation are available in the form of packages, just like software. How much and which information you find in /usr/share/docs also depends on the (documentation) packages installed. If you cannot find the subdirectories mentioned here, check if the respective packages are installed on your system and add them with YaST, if needed.

Novell/SUSE Manuals

We provide HTML and PDF versions of our books in different languages. In the manual subdirectory, find HTML versions of most of the Novell/SUSE manuals available for your product. For an overview of all documentation available for your product refer to the preface of the manuals.

If more than one language is installed, /usr/share/doc/manual may contain different language versions of the manuals. The HTML versions of the Novell/SUSE manuals are also available in the help center of both desktops. For information on where to find the PDF and HTML versions of the books on your installation media, refer to the openSUSE Release Notes. They are available on your installed system under /usr/share/doc/release-notes/ or online at your product-specific Web page at http://www.novell.com/documentation/.

HOWTOs

If the howto package is installed on your system, /usr/share/doc also holds the howto subdirectory, where you find additional documentation for many tasks relating to the setup and operation of Linux software.

Package Documentation

Under packages, find the documentation that is included in the software packages installed on your system. For every package, a subdirectory /usr/share/doc/packages/packagename is created. It often contains README files for the package and sometimes examples, configuration files, or additional scripts. The following list introduces typical files to be found under /usr/share/doc/packages. None of these entries are mandatory and many packages might just include a few of them.

AUTHORS

List of the main developers.

BUGS

Known bugs or malfunctions. Might also contain a link to a Bugzilla Web page where you can search all bugs.

CHANGES , ChangeLog

Summary of changes from version to version. Usually interesting for developers, because it is very detailed.

COPYING , LICENSE

Licensing information.

FAQ

Question and answers collected from mailing lists or newsgroups.

INSTALL

How to install this package on your system. As the package is already installed by the time you get to read this file, you can safely ignore the contents of this file.

README, README.*

General information on the software. For example, for what purpose and how to use it.

TODO

Things that are not implemented yet, but probably will be in the future.

MANIFEST

List of files with a brief summary.

NEWS

Description of what is new in this version.

Man Pages

Man pages are an essential part of any Linux system. They explain the usage of a command and all available options and parameters. Man pages can be accessed with man followed by the name of the command, for example, man ls.

Man pages are displayed directly in the shell. To navigate them, move up and down with Page ↑ and Page ↓. Move between the beginning and the end of a document with Home and End. End this viewing mode by pressing Q. Learn more about the man command itself with man man. Man pages are sorted in categories as shown in Table 35.1, “Man Pages—Categories and Descriptions” (taken from the man page for man itself).

Table 35.1. Man Pages—Categories and Descriptions

Number

Description

1

Executable programs or shell commands

2

System calls (functions provided by the kernel)

3

Library calls (functions within program libraries)

4

Special files (usually found in /dev)

5

File formats and conventions (/etc/fstab)

6

Games

7

Miscellaneous (including macro packages and conventions), for example, man(7), groff(7)

8

System administration commands (usually only for root)

9

Kernel routines (nonstandard)

Each man page consists of several parts labeled NAME , SYNOPSIS , DESCRIPTION , SEE ALSO , LICENSING , and AUTHOR . There may be additional sections available depending on the type of command.

Info Pages

Info pages are another important source of information on your system. Usually, they are more detailed than man pages. To view the info page for a certain command, enter info followed by the name of the command, for example, info ls. You can browse an info page with a viewer directly in the shell and display the different sections, called “nodes.” Use Space to move forward and <— to move backwards. Within a node, you can also browse with Page ↑ and Page ↓ but only Space and <— will take you also to the previous or subsequent node. Press Q to end the viewing mode. Not every man page comes with an info page and vice versa.

Appendix A. An Example Network

This example network is used across all network-related chapters of the openSUSE® documentation.

Appendix B. GNU Licenses

This appendix contains the GNU General Public License and the GNU Free Documentation License.

GNU General Public License

Version 2, June 1991

Copyright (C) 1989, 1991 Free Software Foundation, Inc. 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA

Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

Preamble

The licenses for most software are designed to take away your freedom to share and change it. By contrast, the GNU General Public License is intended to guarantee your freedom to share and change free software--to make sure the software is free for all its users. This General Public License applies to most of the Free Software Foundation’s software and to any other program whose authors commit to using it. (Some other Free Software Foundation software is covered by the GNU Library General Public License instead.) You can apply it to your programs, too.

When we speak of free software, we are referring to freedom, not price. Our General Public Licenses are designed to make sure that you have the freedom to distribute copies of free software (and charge for this service if you wish), that you receive source code or can get it if you want it, that you can change the software or use pieces of it in new free programs; and that you know you can do these things.

To protect your rights, we need to make restrictions that forbid anyone to deny you these rights or to ask you to surrender the rights. These restrictions translate to certain responsibilities for you if you distribute copies of the software, or if you modify it.

For example, if you distribute copies of such a program, whether gratis or for a fee, you must give the recipients all the rights that you have. You must make sure that they, too, receive or can get the source code. And you must show them these terms so they know their rights.

We protect your rights with two steps: (1) copyright the software, and (2) offer you this license which gives you legal permission to copy, distribute and/or modify the software.

Also, for each author’s protection and ours, we want to make certain that everyone understands that there is no warranty for this free software. If the software is modified by someone else and passed on, we want its recipients to know that what they have is not the original, so that any problems introduced by others will not reflect on the original authors’ reputations.

Finally, any free program is threatened constantly by software patents. We wish to avoid the danger that redistributors of a free program will individually obtain patent licenses, in effect making the program proprietary. To prevent this, we have made it clear that any patent must be licensed for everyone’s free use or not licensed at all.

The precise terms and conditions for copying, distribution and modification follow.

GNU GENERAL PUBLIC LICENSE TERMS AND CONDITIONS FOR COPYING, DISTRIBUTION AND MODIFICATION

0.  This License applies to any program or other work which contains a notice placed by the copyright holder saying it may be distributed under the terms of this General Public License. The “Program”, below, refers to any such program or work, and a “work based on the Program” means either the Program or any derivative work under copyright law: that is to say, a work containing the Program or a portion of it, either verbatim or with modifications and/or translated into another language. (Hereinafter, translation is included without limitation in the term “modification”.) Each licensee is addressed as “you”.

Activities other than copying, distribution and modification are not covered by this License; they are outside its scope. The act of running the Program is not restricted, and the output from the Program is covered only if its contents constitute a work based on the Program (independent of having been made by running the Program). Whether that is true depends on what the Program does.

1.  You may copy and distribute verbatim copies of the Program’s source code as you receive it, in any medium, provided that you conspicuously and appropriately publish on each copy an appropriate copyright notice and disclaimer of warranty; keep intact all the notices that refer to this License and to the absence of any warranty; and give any other recipients of the Program a copy of this License along with the Program.

You may charge a fee for the physical act of transferring a copy, and you may at your option offer warranty protection in exchange for a fee.

2.  You may modify your copy or copies of the Program or any portion of it, thus forming a work based on the Program, and copy and distribute such modifications or work under the terms of Section 1 above, provided that you also meet all of these conditions:

a).  You must cause the modified files to carry prominent notices stating that you changed the files and the date of any change.

b).  You must cause any work that you distribute or publish, that in whole or in part contains or is derived from the Program or any part thereof, to be licensed as a whole at no charge to all third parties under the terms of this License.

c).  If the modified program normally reads commands interactively when run, you must cause it, when started running for such interactive use in the most ordinary way, to print or display an announcement including an appropriate copyright notice and a notice that there is no warranty (or else, saying that you provide a warranty) and that users may redistribute the program under these conditions, and telling the user how to view a copy of this License. (Exception: if the Program itself is interactive but does not normally print such an announcement, your work based on the Program is not required to print an announcement.)

These requirements apply to the modified work as a whole. If identifiable sections of that work are not derived from the Program, and can be reasonably considered independent and separate works in themselves, then this License, and its terms, do not apply to those sections when you distribute them as separate works. But when you distribute the same sections as part of a whole which is a work based on the Program, the distribution of the whole must be on the terms of this License, whose permissions for other licensees extend to the entire whole, and thus to each and every part regardless of who wrote it.

Thus, it is not the intent of this section to claim rights or contest your rights to work written entirely by you; rather, the intent is to exercise the right to control the distribution of derivative or collective works based on the Program.

In addition, mere aggregation of another work not based on the Program with the Program (or with a work based on the Program) on a volume of a storage or distribution medium does not bring the other work under the scope of this License.

3.  You may copy and distribute the Program (or a work based on it, under Section 2) in object code or executable form under the terms of Sections 1 and 2 above provided that you also do one of the following:

a).  Accompany it with the complete corresponding machine-readable source code, which must be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,

b).  Accompany it with a written offer, valid for at least three years, to give any third party, for a charge no more than your cost of physically performing source distribution, a complete machine-readable copy of the corresponding source code, to be distributed under the terms of Sections 1 and 2 above on a medium customarily used for software interchange; or,

c).  Accompany it with the information you received as to the offer to distribute corresponding source code. (This alternative is allowed only for noncommercial distribution and only if you received the program in object code or executable form with such an offer, in accord with Subsection b above.)

The source code for a work means the preferred form of the work for making modifications to it. For an executable work, complete source code means all the source code for all modules it contains, plus any associated interface definition files, plus the scripts used to control compilation and installation of the executable. However, as a special exception, the source code distributed need not include anything that is normally distributed (in either source or binary form) with the major components (compiler, kernel, and so on) of the operating system on which the executable runs, unless that component itself accompanies the executable.

If distribution of executable or object code is made by offering access to copy from a designated place, then offering equivalent access to copy the source code from the same place counts as distribution of the source code, even though third parties are not compelled to copy the source along with the object code.

4.  You may not copy, modify, sublicense, or distribute the Program except as expressly provided under this License. Any attempt otherwise to copy, modify, sublicense or distribute the Program is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

5.  You are not required to accept this License, since you have not signed it. However, nothing else grants you permission to modify or distribute the Program or its derivative works. These actions are prohibited by law if you do not accept this License. Therefore, by modifying or distributing the Program (or any work based on the Program), you indicate your acceptance of this License to do so, and all its terms and conditions for copying, distributing or modifying the Program or works based on it.

6.  Each time you redistribute the Program (or any work based on the Program), the recipient automatically receives a license from the original licensor to copy, distribute or modify the Program subject to these terms and conditions. You may not impose any further restrictions on the recipients’ exercise of the rights granted herein. You are not responsible for enforcing compliance by third parties to this License.

7.  If, as a consequence of a court judgment or allegation of patent infringement or for any other reason (not limited to patent issues), conditions are imposed on you (whether by court order, agreement or otherwise) that contradict the conditions of this License, they do not excuse you from the conditions of this License. If you cannot distribute so as to satisfy simultaneously your obligations under this License and any other pertinent obligations, then as a consequence you may not distribute the Program at all. For example, if a patent license would not permit royalty-free redistribution of the Program by all those who receive copies directly or indirectly through you, then the only way you could satisfy both it and this License would be to refrain entirely from distribution of the Program.

If any portion of this section is held invalid or unenforceable under any particular circumstance, the balance of the section is intended to apply and the section as a whole is intended to apply in other circumstances.

It is not the purpose of this section to induce you to infringe any patents or other property right claims or to contest validity of any such claims; this section has the sole purpose of protecting the integrity of the free software distribution system, which is implemented by public license practices. Many people have made generous contributions to the wide range of software distributed through that system in reliance on consistent application of that system; it is up to the author/donor to decide if he or she is willing to distribute software through any other system and a licensee cannot impose that choice.

This section is intended to make thoroughly clear what is believed to be a consequence of the rest of this License.

8.  If the distribution and/or use of the Program is restricted in certain countries either by patents or by copyrighted interfaces, the original copyright holder who places the Program under this License may add an explicit geographical distribution limitation excluding those countries, so that distribution is permitted only in or among countries not thus excluded. In such case, this License incorporates the limitation as if written in the body of this License.

9.  The Free Software Foundation may publish revised and/or new versions of the General Public License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns.

Each version is given a distinguishing version number. If the Program specifies a version number of this License which applies to it and “any later version”, you have the option of following the terms and conditions either of that version or of any later version published by the Free Software Foundation. If the Program does not specify a version number of this License, you may choose any version ever published by the Free Software Foundation.

10.  If you wish to incorporate parts of the Program into other free programs whose distribution conditions are different, write to the author to ask for permission. For software which is copyrighted by the Free Software Foundation, write to the Free Software Foundation; we sometimes make exceptions for this. Our decision will be guided by the two goals of preserving the free status of all derivatives of our free software and of promoting the sharing and reuse of software generally.

NO WARRANTY

11.  BECAUSE THE PROGRAM IS LICENSED FREE OF CHARGE, THERE IS NO WARRANTY FOR THE PROGRAM, TO THE EXTENT PERMITTED BY APPLICABLE LAW. EXCEPT WHEN OTHERWISE STATED IN WRITING THE COPYRIGHT HOLDERS AND/OR OTHER PARTIES PROVIDE THE PROGRAM “AS IS” WITHOUT WARRANTY OF ANY KIND, EITHER EXPRESSED OR IMPLIED, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE. THE ENTIRE RISK AS TO THE QUALITY AND PERFORMANCE OF THE PROGRAM IS WITH YOU. SHOULD THE PROGRAM PROVE DEFECTIVE, YOU ASSUME THE COST OF ALL NECESSARY SERVICING, REPAIR OR CORRECTION.

12.  IN NO EVENT UNLESS REQUIRED BY APPLICABLE LAW OR AGREED TO IN WRITING WILL ANY COPYRIGHT HOLDER, OR ANY OTHER PARTY WHO MAY MODIFY AND/OR REDISTRIBUTE THE PROGRAM AS PERMITTED ABOVE, BE LIABLE TO YOU FOR DAMAGES, INCLUDING ANY GENERAL, SPECIAL, INCIDENTAL OR CONSEQUENTIAL DAMAGES ARISING OUT OF THE USE OR INABILITY TO USE THE PROGRAM (INCLUDING BUT NOT LIMITED TO LOSS OF DATA OR DATA BEING RENDERED INACCURATE OR LOSSES SUSTAINED BY YOU OR THIRD PARTIES OR A FAILURE OF THE PROGRAM TO OPERATE WITH ANY OTHER PROGRAMS), EVEN IF SUCH HOLDER OR OTHER PARTY HAS BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

END OF TERMS AND CONDITIONS

How to Apply These Terms to Your New Programs

If you develop a new program, and you want it to be of the greatest possible use to the public, the best way to achieve this is to make it free software which everyone can redistribute and change under these terms.

To do so, attach the following notices to the program. It is safest to attach them to the start of each source file to most effectively convey the exclusion of warranty; and each file should have at least the “copyright” line and a pointer to where the full notice is found.

one line to give the program’s name and an idea of what it does. Copyright (C) yyyy name of author

   This program is free software; you can redistribute it and/or
   modify it under the terms of the GNU General Public License
   as published by the Free Software Foundation; either version 2
   of the License, or (at your option) any later version.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

Also add information on how to contact you by electronic and paper mail.

If the program is interactive, make it output a short notice like this when it starts in an interactive mode:

   Gnomovision version 69, Copyright (C) year name of author
   Gnomovision comes with ABSOLUTELY NO WARRANTY; for details
   type `show w’. This is free software, and you are welcome
   to redistribute it under certain conditions; type `show c’
   for details.

The hypothetical commands `show w’ and `show c’ should show the appropriate parts of the General Public License. Of course, the commands you use may be called something other than `show w’ and `show c’; they could even be mouse-clicks or menu items--whatever suits your program.

You should also get your employer (if you work as a programmer) or your school, if any, to sign a “copyright disclaimer” for the program, if necessary. Here is a sample; alter the names:

   Yoyodyne, Inc., hereby disclaims all copyright
   interest in the program `Gnomovision’
   (which makes passes at compilers) written
   by James Hacker.

   signature of Ty Coon, 1 April 1989
   Ty Coon, President of Vice

This General Public License does not permit incorporating your program into proprietary programs. If your program is a subroutine library, you may consider it more useful to permit linking proprietary applications with the library. If this is what you want to do, use the GNU Lesser General Public License instead of this License.

GNU Free Documentation License

Version 1.2, November 2002

Copyright (C) 2000,2001,2002 Free Software Foundation, Inc. 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA

Everyone is permitted to copy and distribute verbatim copies of this license document, but changing it is not allowed.

PREAMBLE

The purpose of this License is to make a manual, textbook, or other functional and useful document “free” in the sense of freedom: to assure everyone the effective freedom to copy and redistribute it, with or without modifying it, either commercially or noncommercially. Secondarily, this License preserves for the author and publisher a way to get credit for their work, while not being considered responsible for modifications made by others.

This License is a kind of “copyleft”, which means that derivative works of the document must themselves be free in the same sense. It complements the GNU General Public License, which is a copyleft license designed for free software.

We have designed this License in order to use it for manuals for free software, because free software needs free documentation: a free program should come with manuals providing the same freedoms that the software does. But this License is not limited to software manuals; it can be used for any textual work, regardless of subject matter or whether it is published as a printed book. We recommend this License principally for works whose purpose is instruction or reference.

APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work, in any medium, that contains a notice placed by the copyright holder saying it can be distributed under the terms of this License. Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that work under the conditions stated herein. The “Document”, below, refers to any such manual or work. Any member of the public is a licensee, and is addressed as “you”. You accept the license if you copy, modify or distribute the work in a way requiring permission under copyright law.

A “Modified Version” of the Document means any work containing the Document or a portion of it, either copied verbatim, or with modifications and/or translated into another language.

A “Secondary Section” is a named appendix or a front-matter section of the Document that deals exclusively with the relationship of the publishers or authors of the Document to the Document’s overall subject (or to related matters) and contains nothing that could fall directly within that overall subject. (Thus, if the Document is in part a textbook of mathematics, a Secondary Section may not explain any mathematics.) The relationship could be a matter of historical connection with the subject or with related matters, or of legal, commercial, philosophical, ethical or political position regarding them.

The “Invariant Sections” are certain Secondary Sections whose titles are designated, as being those of Invariant Sections, in the notice that says that the Document is released under this License. If a section does not fit the above definition of Secondary then it is not allowed to be designated as Invariant. The Document may contain zero Invariant Sections. If the Document does not identify any Invariant Sections then there are none.

The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or Back-Cover Texts, in the notice that says that the Document is released under this License. A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25 words.

A “Transparent” copy of the Document means a machine-readable copy, represented in a format whose specification is available to the general public, that is suitable for revising the document straightforwardly with generic text editors or (for images composed of pixels) generic paint programs or (for drawings) some widely available drawing editor, and that is suitable for input to text formatters or for automatic translation to a variety of formats suitable for input to text formatters. A copy made in an otherwise Transparent file format whose markup, or absence of markup, has been arranged to thwart or discourage subsequent modification by readers is not Transparent. An image format is not Transparent if used for any substantial amount of text. A copy that is not “Transparent” is called “Opaque”.

Examples of suitable formats for Transparent copies include plain ASCII without markup, Texinfo input format, LaTeX input format, SGML or XML using a publicly available DTD, and standard-conforming simple HTML, PostScript or PDF designed for human modification. Examples of transparent image formats include PNG, XCF and JPG. Opaque formats include proprietary formats that can be read and edited only by proprietary word processors, SGML or XML for which the DTD and/or processing tools are not generally available, and the machine-generated HTML, PostScript or PDF produced by some word processors for output purposes only.

The “Title Page” means, for a printed book, the title page itself, plus such following pages as are needed to hold, legibly, the material this License requires to appear in the title page. For works in formats which do not have any title page as such, “Title Page” means the text near the most prominent appearance of the work’s title, preceding the beginning of the body of the text.

A section “Entitled XYZ” means a named subunit of the Document whose title either is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in another language. (Here XYZ stands for a specific section name mentioned below, such as “Acknowledgements”, “Dedications”, “Endorsements”, or “History”.) To “Preserve the Title” of such a section when you modify the Document means that it remains a section “Entitled XYZ” according to this definition.

The Document may include Warranty Disclaimers next to the notice which states that this License applies to the Document. These Warranty Disclaimers are considered to be included by reference in this License, but only as regards disclaiming warranties: any other implication that these Warranty Disclaimers may have is void and has no effect on the meaning of this License.

VERBATIM COPYING

You may copy and distribute the Document in any medium, either commercially or noncommercially, provided that this License, the copyright notices, and the license notice saying this License applies to the Document are reproduced in all copies, and that you add no other conditions whatsoever to those of this License. You may not use technical measures to obstruct or control the reading or further copying of the copies you make or distribute. However, you may accept compensation in exchange for copies. If you distribute a large enough number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and you may publicly display copies.

COPYING IN QUANTITY

If you publish printed copies (or copies in media that commonly have printed covers) of the Document, numbering more than 100, and the Document’s license notice requires Cover Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both covers must also clearly and legibly identify you as the publisher of these copies. The front cover must present the full title with all words of the title equally prominent and visible. You may add other material on the covers in addition. Copying with changes limited to the covers, as long as they preserve the title of the Document and satisfy these conditions, can be treated as verbatim copying in other respects.

If the required texts for either cover are too voluminous to fit legibly, you should put the first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto adjacent pages.

If you publish or distribute Opaque copies of the Document numbering more than 100, you must either include a machine-readable Transparent copy along with each Opaque copy, or state in or with each Opaque copy a computer-network location from which the general network-using public has access to download using public-standard network protocols a complete Transparent copy of the Document, free of added material. If you use the latter option, you must take reasonably prudent steps, when you begin distribution of Opaque copies in quantity, to ensure that this Transparent copy will remain thus accessible at the stated location until at least one year after the last time you distribute an Opaque copy (directly or through your agents or retailers) of that edition to the public.

It is requested, but not required, that you contact the authors of the Document well before redistributing any large number of copies, to give them a chance to provide you with an updated version of the Document.

MODIFICATIONS

You may copy and distribute a Modified Version of the Document under the conditions of sections 2 and 3 above, provided that you release the Modified Version under precisely this License, with the Modified Version filling the role of the Document, thus licensing distribution and modification of the Modified Version to whoever possesses a copy of it. In addition, you must do these things in the Modified Version:

A.  Use in the Title Page (and on the covers, if any) a title distinct from that of the Document, and from those of previous versions (which should, if there were any, be listed in the History section of the Document). You may use the same title as a previous version if the original publisher of that version gives permission.

B.  List on the Title Page, as authors, one or more persons or entities responsible for authorship of the modifications in the Modified Version, together with at least five of the principal authors of the Document (all of its principal authors, if it has fewer than five), unless they release you from this requirement.

C.  State on the Title page the name of the publisher of the Modified Version, as the publisher.

D.  Preserve all the copyright notices of the Document.

E.  Add an appropriate copyright notice for your modifications adjacent to the other copyright notices.

F.  Include, immediately after the copyright notices, a license notice giving the public permission to use the Modified Version under the terms of this License, in the form shown in the Addendum below.

G.  Preserve in that license notice the full lists of Invariant Sections and required Cover Texts given in the Document’s license notice.

H.  Include an unaltered copy of this License.

I.  Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating at least the title, year, new authors, and publisher of the Modified Version as given on the Title Page. If there is no section Entitled “History” in the Document, create one stating the title, year, authors, and publisher of the Document as given on its Title Page, then add an item describing the Modified Version as stated in the previous sentence.

J.  Preserve the network location, if any, given in the Document for public access to a Transparent copy of the Document, and likewise the network locations given in the Document for previous versions it was based on. These may be placed in the “History” section. You may omit a network location for a work that was published at least four years before the Document itself, or if the original publisher of the version it refers to gives permission.

K.  For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title of the section, and preserve in the section all the substance and tone of each of the contributor acknowledgements and/or dedications given therein.

L.  Preserve all the Invariant Sections of the Document, unaltered in their text and in their titles. Section numbers or the equivalent are not considered part of the section titles.

M.  Delete any section Entitled “Endorsements”. Such a section may not be included in the Modified Version.

N.  Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title with any Invariant Section.

O.  Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or appendices that qualify as Secondary Sections and contain no material copied from the Document, you may at your option designate some or all of these sections as invariant. To do this, add their titles to the list of Invariant Sections in the Modified Version’s license notice. These titles must be distinct from any other section titles.

You may add a section Entitled “Endorsements”, provided it contains nothing but endorsements of your Modified Version by various parties--for example, statements of peer review or that the text has been approved by an organization as the authoritative definition of a standard.

You may add a passage of up to five words as a Front-Cover Text, and a passage of up to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added by (or through arrangements made by) any one entity. If the Document already includes a cover text for the same cover, previously added by you or by arrangement made by the same entity you are acting on behalf of, you may not add another; but you may replace the old one, on explicit permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License give permission to use their names for publicity for or to assert or imply endorsement of any Modified Version.

COMBINING DOCUMENTS

You may combine the Document with other documents released under this License, under the terms defined in section 4 above for modified versions, provided that you include in the combination all of the Invariant Sections of all of the original documents, unmodified, and list them all as Invariant Sections of your combined work in its license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and multiple identical Invariant Sections may be replaced with a single copy. If there are multiple Invariant Sections with the same name but different contents, make the title of each such section unique by adding at the end of it, in parentheses, the name of the original author or publisher of that section if known, or else a unique number. Make the same adjustment to the section titles in the list of Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled “History” in the various original documents, forming one section Entitled “History”; likewise combine any sections Entitled “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections Entitled “Endorsements”.

COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents released under this License, and replace the individual copies of this License in the various documents with a single copy that is included in the collection, provided that you follow the rules of this License for verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute it individually under this License, provided you insert a copy of this License into the extracted document, and follow this License in all other respects regarding verbatim copying of that document.

AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate and independent documents or works, in or on a volume of a storage or distribution medium, is called an “aggregate” if the copyright resulting from the compilation is not used to limit the legal rights of the compilation’s users beyond what the individual works permit. When the Document is included in an aggregate, this License does not apply to the other works in the aggregate which are not themselves derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these copies of the Document, then if the Document is less than one half of the entire aggregate, the Document’s Cover Texts may be placed on covers that bracket the Document within the aggregate, or the electronic equivalent of covers if the Document is in electronic form. Otherwise they must appear on printed covers that bracket the whole aggregate.

TRANSLATION

Translation is considered a kind of modification, so you may distribute translations of the Document under the terms of section 4. Replacing Invariant Sections with translations requires special permission from their copyright holders, but you may include translations of some or all Invariant Sections in addition to the original versions of these Invariant Sections. You may include a translation of this License, and all the license notices in the Document, and any Warranty Disclaimers, provided that you also include the original English version of this License and the original versions of those notices and disclaimers. In case of a disagreement between the translation and the original version of this License or a notice or disclaimer, the original version will prevail.

If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”, the requirement (section 4) to Preserve its Title (section 1) will typically require changing the actual title.

TERMINATION

You may not copy, modify, sublicense, or distribute the Document except as expressly provided for under this License. Any other attempt to copy, modify, sublicense or distribute the Document is void, and will automatically terminate your rights under this License. However, parties who have received copies, or rights, from you under this License will not have their licenses terminated so long as such parties remain in full compliance.

FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions of the GNU Free Documentation License from time to time. Such new versions will be similar in spirit to the present version, but may differ in detail to address new problems or concerns. See http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number. If the Document specifies that a particular numbered version of this License “or any later version” applies to it, you have the option of following the terms and conditions either of that specified version or of any later version that has been published (not as a draft) by the Free Software Foundation. If the Document does not specify a version number of this License, you may choose any version ever published (not as a draft) by the Free Software Foundation.

ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of the License in the document and put the following copyright and license notices just after the title page:

   Copyright (c) YEAR YOUR NAME.
   Permission is granted to copy, distribute and/or modify this document
   under the terms of the GNU Free Documentation License, Version 1.2
   only as published by the Free Software Foundation;
   with the Invariant Section being this copyright notice and license.
   A copy of the license is included in the section entitled “GNU
   Free Documentation License”.

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the “with...Texts.” line with this:

   with the Invariant Sections being LIST THEIR TITLES, with the
   Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.

If you have Invariant Sections without Cover Texts, or some other combination of the three, merge those two alternatives to suit the situation.

If your document contains nontrivial examples of program code, we recommend releasing these examples in parallel under your choice of free software license, such as the GNU General Public License, to permit their use in free software.