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<p><a name="ch-customizing"></a></p>
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The Debian GNU/Linux FAQ
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<br>Chapter 10 - Customizing your installation of Debian GNU/Linux
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<h2><a name="s-papersize"></a>10.1 How can I ensure that all programs use the same paper size?</h2>
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Install the <code>libpaper1</code> package, and it will ask you for a
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system-wide default paper size. This setting will be kept in the file
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<samp>/etc/papersize</samp>.
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Users can override the paper size setting using the <samp>PAPERSIZE</samp>
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environment variable. For details, see the manual page
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<code>papersize(5)</code>.
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<h2><a name="s-hardwareaccess"></a>10.2 How can I provide access to hardware peripherals, without compromising security?</h2>
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Many device files in the <samp>/dev</samp> directory belong to some predefined
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groups. For example, <samp>/dev/fd0</samp> belongs to the <samp>floppy</samp>
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group, and <samp>/dev/dsp</samp> belongs to the <samp>audio</samp> group.
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If you want a certain user to have access to one of these devices, just add the
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user to the group the device belongs to, i.e. do:
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This way you won't have to change the file permissions on the device.
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<h2><a name="s-consolefont"></a>10.3 How do I load a console font on startup the Debian way?</h2>
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The <code>kbd</code> and <code>console-tools</code> packages support this, edit
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<samp>/etc/kbd/config</samp> or <samp>/etc/console-tools/config</samp> files.
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<h2><a name="s-appdefaults"></a>10.4 How can I configure an X11 program's application defaults?</h2>
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Debian's X programs will install their application resource data in the
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<samp>/etc/X11/app-defaults/</samp> directory. If you want to customize X
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applications globally, put your customizations in those files. They are marked
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as configuration files, so their contents will be preserved during upgrades.
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<h2><a name="s-booting"></a>10.5 Every distribution seems to have a different boot-up method. Tell me about Debian's.</h2>
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Like all Unices, Debian boots up by executing the program <samp>init</samp>.
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The configuration file for <samp>init</samp> (which is
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<samp>/etc/inittab</samp>) specifies that the first script to be executed
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should be <samp>/etc/init.d/rcS</samp>. This script runs all of the scripts in
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<samp>/etc/rcS.d/</samp> by sourcing or forking subprocess depending on their
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file extension to perform initialization such as to check and to mount file
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systems, to load modules, to start the network services, to set the clock, and
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to perform other initialization. Then, for compatibility, it runs the files
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(except those with a `.'in the filename) in <samp>/etc/rc.boot/</samp> too.
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Any scripts in the latter directory are usually reserved for system
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administrator use, and using them in packages is deprecated.
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After completing the boot process, <samp>init</samp> executes all start scripts
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in a directory specified by the default runlevel (this runlevel is given by the
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entry for <samp>id</samp> in <samp>/etc/inittab</samp>). Like most System V
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compatible Unices, Linux has 7 runlevels:
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1 (single-user mode),
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2 through 5 (various multi-user modes), and
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6 (reboot the system).
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Debian systems come with id=2, which indicates that the default runlevel will
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be '2' when the multi-user state is entered, and the scripts in
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<samp>/etc/rc2.d/</samp> will be run.
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In fact, the scripts in any of the directories, <samp>/etc/rcN.d/</samp> are
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just symbolic links back to scripts in <samp>/etc/init.d/</samp>. However, the
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<em>names</em> of the files in each of the <samp>/etc/rcN.d/</samp> directories
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are selected to indicate the <em>way</em> the scripts in
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<samp>/etc/init.d/</samp> will be run. Specifically, before entering any
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runlevel, all the scripts beginning with 'K' are run; these scripts kill
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services. Then all the scripts beginning with 'S' are run; these scripts start
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services. The two-digit number following the 'K' or 'S' indicates the order in
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which the script is run. Lower numbered scripts are executed first.
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This approach works because the scripts in <samp>/etc/init.d/</samp> all take
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an argument which can be either `start', `stop', `reload', `restart' or
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`force-reload' and will then do the task indicated by the argument. These
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scripts can be used even after a system has been booted, to control various
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For example, with the argument `reload' the command
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/etc/init.d/sendmail reload
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sends the sendmail daemon a signal to reread its configuration file. (BTW,
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Debian supplies <code>invoke-rc.d</code> as a wrapper for invoking the scripts
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in <samp>/etc/init.d/</samp>.)
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<h2><a name="s-custombootscripts"></a>10.6 It looks as if Debian does not use <samp>rc.local</samp> to customize the boot process; what facilities are provided?</h2>
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Suppose a system needs to execute script <samp>foo</samp> on start-up, or on
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entry to a particular (System V) runlevel. Then the system administrator
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Enter the script <samp>foo</samp> into the directory <samp>/etc/init.d/</samp>.
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Run the Debian command <samp>update-rc.d</samp> with appropriate arguments, to
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set up links between the (command-line-specified) directories rc?.d and
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<samp>/etc/init.d/foo</samp>. Here, '?' is a number from 0 through 6 and
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corresponds to each of the System V runlevels.
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The command <samp>update-rc.d</samp> will set up links between files in the
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directories rc?.d and the script in <samp>/etc/init.d/</samp>. Each link will
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begin with a 'S' or a 'K', followed by a number, followed by the name of the
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script. Scripts beginning with 'S' in <samp>/etc/rcN.d/</samp> are executed
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when runlevel <samp>N</samp> is entered. Scripts beginning with a 'K' are
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executed when leaving runlevel <samp>N</samp>.
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One might, for example, cause the script <samp>foo</samp> to execute at
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boot-up, by putting it in <samp>/etc/init.d/</samp> and installing the links
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with <samp>update-rc.d foo defaults 19</samp>. The argument 'defaults' refers
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to the default runlevels, which are 2 through 5. The argument '19' ensures
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that <samp>foo</samp> is called before any scripts containing numbers 20 or
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<h2><a name="s-interconffiles"></a>10.7 How does the package management system deal with packages that contain configuration files for other packages?</h2>
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Some users wish to create, for example, a new server by installing a group of
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Debian packages and a locally generated package consisting of configuration
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files. This is not generally a good idea, because <code>dpkg</code> will not
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know about those configuration files if they are in a different package, and
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may write conflicting configurations when one of the initial "group"
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of packages is upgraded.
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Instead, create a local package that modifies the configuration files of the
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"group" of Debian packages of interest. Then <code>dpkg</code> and
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the rest of the package management system will see that the files have been
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modified by the local "sysadmin" and will not try to overwrite them
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when those packages are upgraded.
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<h2><a name="s-divert"></a>10.8 How do I override a file installed by a package, so that a different version can be used instead?</h2>
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Suppose a sysadmin or local user wishes to use a program
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"login-local" rather than the program "login" provided by
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the Debian <code>login</code> package.
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Do <strong>not</strong>:
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Overwrite <samp>/bin/login</samp> with <samp>login-local</samp>.
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The package management system will not know about this change, and will simply
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overwrite your custom <samp>/bin/login</samp> whenever <samp>login</samp> (or
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any package that provides <samp>/bin/login</samp>) is installed or updated.
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dpkg-divert --divert /bin/login.debian /bin/login
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in order to cause all future installations of the Debian <code>login</code>
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package to write the file <samp>/bin/login</samp> to
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<samp>/bin/login.debian</samp> instead.
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cp login-local /bin/login
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to move your own locally-built program into place.
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Details are given in the manual page <code>dpkg-divert(8)</code>.
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<h2><a name="s-localpackages"></a>10.9 How can I have my locally-built package included in the list of available packages that the package management system knows about?</h2>
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dpkg-scanpackages BIN_DIR OVERRIDE_FILE [PATHPREFIX] > my_Packages
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BIN-DIR is a directory where Debian archive files (which usually have an
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extension of ".deb") are stored.
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OVERRIDE_FILE is a file that is edited by the distribution maintainers and is
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usually stored on a Debian FTP archive at <samp>indices/override.main.gz</samp>
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for the Debian packages in the "main" distribution. You can ignore
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this for local packages.
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PATHPREFIX is an <em>optional</em> string that can be prepended to the
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<samp>my_Packages</samp> file being produced.
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Once you have built the file <samp>my_Packages</samp>, tell the package
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management system about it by using the command:
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dpkg --merge-avail my_Packages
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If you are using APT, you can add the local repository to your
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<code>sources.list(5)</code> file, too.
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<h2><a name="s-diverse"></a>10.10 Some users like mawk, others like gawk; some like vim, others like elvis; some like trn, others like tin; how does Debian support diversity?</h2>
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There are several cases where two packages provide two different versions of a
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program, both of which provide the same core functionality. Users might prefer
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one over another out of habit, or because the user interface of one package is
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somehow more pleasing than the interface of another. Other users on the same
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system might make a different choice.
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Debian uses a "virtual" package system to allow system administrators
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to choose (or let users choose) their favorite tools when there are two or more
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that provide the same basic functionality, yet satisfy package dependency
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requirements without specifying a particular package.
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For example, there might exist two different versions of newsreaders on a
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system. The news server package might 'recommend' that there exist
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<em>some</em> news reader on the system, but the choice of <samp>tin</samp> or
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<samp>trn</samp> is left up to the individual user. This is satisfied by
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having both the <code>tin</code> and <code>trn</code> packages provide the
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virtual package <code>news-reader</code>. <em>Which</em> program is invoked is
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determined by a link pointing from a file with the virtual package name
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<samp>/etc/alternatives/news-reader</samp> to the selected file, e.g.,
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<samp>/usr/bin/trn</samp>.
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A single link is insufficient to support full use of an alternate program;
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normally, manual pages, and possibly other supporting files must be selected as
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well. The Perl script <samp>update-alternatives</samp> provides a way of
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ensuring that all the files associated with a specified package are selected as
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For example, to check what executables provide `x-window-manager', run:
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update-alternatives --display x-window-manager
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If you want to change it, run:
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update-alternatives --config x-window-manager
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And follow the instructions on the screen (basically, press the number next to
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the entry you'd like better).
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If a package doesn't register itself as a window manager for some reason (file
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a bug if it's in error), or if you use a window manager from /usr/local
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directory, the selections on screen won't contain your preferred entry. You
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can update the link through command line options, like this:
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update-alternatives --install /usr/bin/x-window-manager \
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x-window-manager /usr/local/bin/wmaker-cvs 50
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The first argument to `--install' option is the symlink that points to
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/etc/alternatives/NAME, where NAME is the second argument. The third argument
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is the program to which /etc/alternatives/NAME should point to, and the fourth
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argument is the priority (larger value means the alternative will more probably
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get picked automatically).
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To remove an alternative you added, simply run:
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update-alternatives --remove x-window-manager /usr/local/bin/wmaker-cvs
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[ <a href="ch-basic_defs.en.html">1</a> ]
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[ <a href="ch-getting.en.html">2</a> ]
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[ <a href="ch-compat.en.html">3</a> ]
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[ <a href="ch-software.en.html">4</a> ]
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[ <a href="ch-ftparchives.en.html">5</a> ]
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[ <a href="ch-pkg_basics.en.html">6</a> ]
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[ <a href="ch-pkgtools.en.html">7</a> ]
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[ <a href="ch-uptodate.en.html">8</a> ]
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[ <a href="ch-kernel.en.html">9</a> ]
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[ <a href="ch-support.en.html">11</a> ]
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[ <a href="ch-contributing.en.html">12</a> ]
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[ <a href="ch-redistrib.en.html">13</a> ]
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[ <a href="ch-faqinfo.en.html">15</a> ]
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[ <a href="ch-support.en.html">next</a> ]
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The Debian GNU/Linux FAQ
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version 3.1.5, 17 January 2007<br>
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Authors are listed at <a href="ch-faqinfo.en.html#s-authors">Debian FAQ Authors</a><br>
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