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<title>The Debian GNU/Linux FAQ - Debian and the kernel</title>
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<p><a name="ch-kernel"></a></p>
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<h1>
The Debian GNU/Linux FAQ
<br>Chapter 9 - Debian and the kernel
</h1>
<hr>
<h2><a name="s-non-debian-kernel"></a>9.1 Can I install and compile a kernel without some Debian-specific tweaking?</h2>
<p>
Yes.
</p>
<p>
There's only one common catch: the Debian C libraries are built with the most
recent <em>stable</em> releases of the <strong>kernel</strong> headers. If you
happen to need to compile a program with kernel headers newer than the ones
from the stable branch, then you should either upgrade the package containing
the headers (<code>libc6-dev</code>), or use the new headers from an unpacked
tree of the newer kernel. That is, if the kernel sources are in
<code>/usr/src/linux</code>, then you should add
<samp>-I/usr/src/linux/include/</samp> to your command line when compiling.
</p>
<hr>
<h2><a name="s-customkernel"></a>9.2 What tools does Debian provide to build custom kernels?</h2>
<p>
Users who wish to (or must) build a custom kernel are encouraged to download
the package <code>kernel-package</code>. This package contains the script to
build the kernel package, and provides the capability to create a Debian
<code>kernel-image-<var>version</var></code> package just by running the
command
</p>
<pre>
make-kpkg kernel_image
</pre>
<p>
in the top-level kernel source directory. Help is available by executing the
command
</p>
<pre>
make-kpkg --help
</pre>
<p>
and through the manual page <code>make-kpkg(1)</code>.
</p>
<p>
Users must separately download the source code for the most recent kernel (or
the kernel of their choice) from their favorite Linux archive site, unless a
<code>kernel-source-<var>version</var></code> package is available (where
<var>version</var> stands for the kernel version).
</p>
<p>
Detailed instructions for using the <code>kernel-package</code> package are
given in the file <code>/usr/share/doc/kernel-package/README.gz</code>.
Briefly, one should:
</p>
<ul>
<li>
<p>
Unpack the kernel sources, and <samp>cd</samp> to the newly created directory.
</p>
</li>
</ul>
<ul>
<li>
<p>
Modify the kernel configuration using one of these commands:
</p>
<ul>
<li>
<p>
<samp>make config</samp> (for a text-based interface).
</p>
</li>
</ul>
<ul>
<li>
<p>
<samp>make menuconfig</samp> (for an ncurses-based menu driven interface).
Note that to use this option, the <code>libncurses5-dev</code> package must be
installed.
</p>
</li>
</ul>
<ul>
<li>
<p>
<samp>make xconfig</samp> (for an X11 interface). Using this option requires
that relevant X and Tcl/Tk packages be installed.
</p>
</li>
</ul>
<p>
Any of the above steps generates a new <samp>.config</samp> in the top-level
kernel source directory.
</p>
</li>
</ul>
<ul>
<li>
<p>
Execute the command: <samp>make-kpkg -rev Custom.<var>N</var>
kernel_image</samp>, where <var>N</var> is a revision number assigned by the
user. The new Debian archive thus formed would have revision
Custom.<var>N</var>, e.g. <code>kernel-image-2.2.14_Custom.1_i386.deb</code>
for the Linux kernel 2.2.14 on i386.
</p>
</li>
</ul>
<ul>
<li>
<p>
Install the package created.
</p>
<ul>
<li>
<p>
Run <samp>dpkg --install
../kernel-image-<var>VVV</var>_Custom.<var>N</var>_i386.deb</samp> to install
the kernel itself. The installation script will:
</p>
<ul>
<li>
<p>
run the boot loader (grub, LILO or some other) if needed,
</p>
</li>
</ul>
<ul>
<li>
<p>
install the custom kernel in
<code>/boot/vmlinuz_<var>VVV</var>-Custom.<var>N</var></code>, and set up
appropriate symbolic links to the most recent kernel version.
</p>
</li>
</ul>
<ul>
<li>
<p>
prompt the user to make a boot floppy. This boot floppy will contain the raw
kernel only. See <a href="#s-custombootdisk">How can I make a custom boot
floppy?, Section 9.3</a>.
</p>
</li>
</ul>
</li>
</ul>
<ul>
<li>
<p>
To employ secondary boot loaders such as <code>loadlin</code>, copy this image
to other locations (e.g. to an <samp>MS-DOS</samp> partition).
</p>
</li>
</ul>
</li>
</ul>
<hr>
<h2><a name="s-custombootdisk"></a>9.3 How can I make a custom boot floppy?</h2>
<p>
This task is greatly aided by the Debian package <code>boot-floppies</code>,
normally found in the <samp>admin</samp> section of the Debian FTP archive.
Shell scripts in this package produce boot floppies in the
<samp>SYSLINUX</samp> format. These are <samp>MS-DOS</samp> formatted floppies
whose master boot records have been altered so that they boot Linux directly
(or whatever other operating system has been defined in the
<code>syslinux.cfg</code> file on the floppy). Other scripts in this package
produce emergency root disks and can even reproduce the base disks.
</p>
<p>
You will find more information about this in the
<code>/usr/share/doc/boot-floppies/README</code> file after installing the
<code>boot-floppies</code> package.
</p>
<hr>
<h2><a name="s-modules"></a>9.4 What special provisions does Debian provide to deal with modules?</h2>
<p>
Debian's <code>modconf</code> package provides a shell script
(<code>/usr/sbin/modconf</code>) which can be used to customize the
configuration of modules. This script presents a menu-based interface,
prompting the user for particulars on the loadable device drivers in his
system. The responses are used to customize the file
<code>/etc/modules.conf</code> (which lists aliases, and other arguments that
must be used in conjunction with various modules) through files in
<code>/etc/modutils/</code>, and <code>/etc/modules</code> (which lists the
modules that must be loaded at boot time).
</p>
<p>
Like the (new) <code>Configure.help</code> files that are now available to
support the construction of custom kernels, the <code>modconf</code> package
comes with a series of help files (in <code>/usr/lib/modules_help/</code>)
which provide detailed information on appropriate arguments for each of the
modules.
</p>
<hr>
<h2><a name="s-removeoldkernel"></a>9.5 Can I safely de-install an old kernel package, and if so, how?</h2>
<p>
Yes. The <code>kernel-image-<var>NNN</var>.prerm</code> script checks to see
whether the kernel you are currently running is the same as the kernel you are
trying to de-install. Therefore you can remove unwanted kernel image packages
using this command:
</p>
<pre>
dpkg --purge --force-remove-essential kernel-image-<var>NNN</var>
</pre>
<p>
(replace <var>NNN</var> with your kernel version and revision number, of
course)
</p>
<hr>
<p>
[ <a href="ch-uptodate.en.html">previous</a> ]
[ <a href="index.en.html#contents">Contents</a> ]
[ <a href="ch-basic_defs.en.html">1</a> ]
[ <a href="ch-getting.en.html">2</a> ]
[ <a href="ch-compat.en.html">3</a> ]
[ <a href="ch-software.en.html">4</a> ]
[ <a href="ch-ftparchives.en.html">5</a> ]
[ <a href="ch-pkg_basics.en.html">6</a> ]
[ <a href="ch-pkgtools.en.html">7</a> ]
[ <a href="ch-uptodate.en.html">8</a> ]
[ 9 ]
[ <a href="ch-customizing.en.html">10</a> ]
[ <a href="ch-support.en.html">11</a> ]
[ <a href="ch-contributing.en.html">12</a> ]
[ <a href="ch-redistrib.en.html">13</a> ]
[ <a href="ch-nexttime.en.html">14</a> ]
[ <a href="ch-faqinfo.en.html">15</a> ]
[ <a href="ch-customizing.en.html">next</a> ]
</p>
<hr>
<p>
The Debian GNU/Linux FAQ
</p>
<address>
version 3.1.5, 17 January 2007<br>
<br>
Authors are listed at <a href="ch-faqinfo.en.html#s-authors">Debian FAQ Authors</a><br>
<br>
</address>
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