lfs-book/chapter08/kernel.xml

<sect1 id="ch-bootable-kernel" xreflabel="Linux">
<title>Installing Linux-&kernel-version;</title>
<?dbhtml filename="kernel.html" dir="chapter08"?>

<para>The Linux package contains the kernel and the header files.</para>

<screen>Estimated build time:           &kernel-time;
Estimated required disk space:  &kernel-compsize;</screen>

&aa-kernel-down;
&aa-kernel-dep;

<sect2><title>&nbsp;</title><para>&nbsp;</para></sect2>

<sect2>
<title>Installation of the kernel</title>

<para>Building the kernel involves a few steps: configuration, compilation, and
installation. If you don't like the way this book configures the kernel, view
the <filename>README</filename> file in the kernel source tree for alternative
methods.</para>

<para>Prepare for compilation by running the following command:</para>

<screen><userinput>make mrproper</userinput></screen>

<para>This ensures that the kernel tree is absolutely clean. The kernel team
recommends that this command be issued prior to <emphasis>each</emphasis>
kernel compilation. You shouldn't rely on the source tree being clean after
untarring.</para>

<para>Configure the kernel via a menu-driven interface:</para>

<screen><userinput>make menuconfig</userinput></screen>

<para><userinput>make oldconfig</userinput> may be more appropriate in some
situations. See the <filename>README</filename> file for more
information.</para>

<para>If you wish, you may skip kernel configuration by simply copying the
kernel config file, <filename>.config</filename>, from your host system
(assuming it is available) to the unpacked <filename
class="directory">linux-&kernel-version;</filename> directory. However, we
don't recommend this option. You're much better off exploring all the
configuration menus and creating your own kernel configuration from
scratch.</para>

<para>For POSIX shared memory support, ensure that the kernel config option
"Virtual memory file system support" is enabled. It resides within the
"File systems" menu and is normally enabled by default.</para>

<para>Verify dependencies and create dependency information files:</para>

<screen><userinput>make CC=/opt/gcc-2.95.3/bin/gcc dep</userinput></screen>

<para>Compile the kernel image:</para>

<screen><userinput>make CC=/opt/gcc-2.95.3/bin/gcc bzImage</userinput></screen>

<para>Compile the drivers which have been configured as modules:</para>

<screen><userinput>make CC=/opt/gcc-2.95.3/bin/gcc modules</userinput></screen>

<para>If you intend to use kernel modules, you will need an
<filename>/etc/modules.conf</filename> file. Information pertaining
to modules and to kernel configuration in general may be found in the
kernel documentation, which is found in the
<filename>linux-&kernel-version;/Documentation</filename> directory. The
modules.conf man page and the kernel HOWTO at
<ulink url="&tldp-root;HOWTO/Kernel-HOWTO.html"/> may also be of
interest to you.</para>

<para>Install the modules:</para>

<screen><userinput>make CC=/opt/gcc-2.95.3/bin/gcc modules_install</userinput></screen>

<para>As nothing is complete without documentation, build the manual pages
that come with the kernel:</para>

<screen><userinput>make mandocs</userinput></screen>

<para>And install these pages:</para>

<screen><userinput>cp -a Documentation/man /usr/share/man/man9</userinput></screen>

<para>Kernel compilation has finished but more steps are required to complete
the installation. Some files need to be copied to the <filename>/boot</filename>
directory.</para>

<para>The path to the kernel image may vary depending on the platform you're
using. Issue the following command to install the kernel:</para>

<screen><userinput>cp arch/i386/boot/bzImage /boot/lfskernel</userinput></screen>

<para><filename>System.map</filename> is a symbol file for the kernel. It maps
the function entrypoints of every function in the kernel API, as well as the
addresses of the kernel data structures for the running kernel. Issue the
following command to install the map file:</para>

<screen><userinput>cp System.map /boot</userinput></screen>

<para><filename>.config</filename> is the kernel configuration file that was
produced by the <command>make menuconfig</command> step above. It contains all
the config selections for the kernel that was just compiled. It's a good idea
to keep this file for future reference:</para>

<screen><userinput>cp .config /boot/config-lfskernel</userinput></screen>

<para>It is important to note that the files in the kernel source directory are
not owned by <emphasis>root</emphasis>. Whenever you unpack a package as user
<emphasis>root</emphasis> (like we did here inside chroot), the files end up
having the user and group IDs of whatever they were on the packager's computer.
This is usually not a problem for any other package you install because you
remove the source tree after the installation. But the Linux source tree is
often kept around for a long time, so there's a chance that whatever user ID
the packager used will be assigned to somebody on your machine and then that
person would have write access to the kernel source.</para>

<para>If you are going to keep the kernel source tree around, you may want to
run <userinput>chown -R 0:0</userinput> on the
<filename>linux-&kernel-version;</filename> directory to ensure all files are
owned by user <emphasis>root</emphasis>.</para>

</sect2>

&aa-kernel-shortdesc;
&aa-kernel-desc;

</sect1>