source: BOOK/bootable/x86/kernel.xml @ b169dfe

Last change on this file since b169dfe was b169dfe, checked in by Chris Staub <chris@…>, 15 years ago

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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "" [
4  <!ENTITY % general-entities SYSTEM "../../general.ent">
5  %general-entities;
8<sect1 id="ch-bootable-kernel" role="wrap">
9  <?dbhtml filename="kernel.html"?>
11  <title>Linux-&linux-version;</title>
13  <indexterm zone="ch-bootable-kernel">
14    <primary sortas="a-Linux">Linux</primary>
15  </indexterm>
17  <sect2 role="package"><title/>
18    <para>The Linux package contains the Linux kernel.</para>
20  </sect2>
22  <sect2 role="installation">
23    <title>Installation of the kernel</title>
25    <para os="a">Building the kernel involves a few steps&mdash;configuration,
26    compilation, and installation. Read the <filename>README</filename>
27    file in the kernel source tree for alternative methods to the way this
28    book configures the kernel.</para>
30    <para os="b">Prepare for compilation by running the following command:</para>
32<screen os="c"><userinput>make mrproper</userinput></screen>
34    <para os="d">This ensures that the kernel tree is absolutely clean. The
35    kernel team recommends that this command be issued prior to each
36    kernel compilation. Do not rely on the source tree being clean after
37    un-tarring.</para>
39    <para os="h">Configure the kernel via a menu-driven interface.
40    Please note that the udev bootscript requires "rtc" and "tmpfs" to be
41    enabled and built into the kernel, not as modules. CBLFS has
42    some information regarding particular kernel configuration requirements of
43    packages outside of CLFS at <ulink
44    url="&cblfs-root;"/>:</para>
46<screen os="i"><userinput>make menuconfig</userinput></screen>
48    <para os="j">Alternatively, <command>make oldconfig</command> may be more
49    appropriate in some situations. See the <filename>README</filename>
50    file for more information.</para>
52    <para os="k">If desired, skip kernel configuration by copying the kernel
53    config file, <filename>.config</filename>, from the host system
54    (assuming it is available) to the root directory of the unpacked kernel
55    sources. However, we do not recommend this option. It is often better
56    to explore all the configuration menus and create the kernel configuration
57    from scratch.</para>
59    <para os="m">Compile the kernel image and modules:</para>
61<screen os="n"><userinput>make</userinput></screen>
63    <para os="o">If using kernel modules, an
64    <filename>/etc/modprobe.conf</filename> file may be needed.
65    Information pertaining to modules and kernel configuration is
66    located in the kernel documentation in the <filename
67    class="directory">Documentation</filename> directory of the kernel
68    sources tree. Also, <filename>modprobe.conf(5)</filename> may
69    be of interest.</para>
71    <para os="p">Be very careful when reading other documentation relating to
72    kernel modules because it usually applies to 2.4.x kernels only. As
73    far as we know, kernel configuration issues specific to Hotplug and
74    Udev are not documented. The problem is that Udev will create a device
75    node only if Hotplug or a user-written script inserts the corresponding
76    module into the kernel, and not all modules are detectable by Hotplug.
77    Note that statements like the one below in the
78    <filename>/etc/modprobe.conf</filename> file do not work with Udev:</para>
80<screen os="q"><literal>alias char-major-XXX some-module</literal></screen>
82    <para os="r">Because of the complications with Udev and modules,
83    we strongly recommend starting with a completely non-modular kernel
84    configuration, especially if this is the first time using Udev.</para>
86    <para os="s">Install the modules, if the kernel configuration uses
87    them:</para>
89<screen os="t"><userinput>make modules_install</userinput></screen>
91    <para os="u">After kernel compilation is complete, additional steps are
92    required to complete the installation. Some files need to be copied to
93    the <filename class="directory">/boot</filename> directory.</para>
95    <para os="v">Issue the following command to install the kernel:</para>
97<screen><userinput>cp -v arch/i386/boot/bzImage /boot/clfskernel-&linux-version;</userinput></screen>
99    <para os="w"><filename></filename> is a symbol file for the kernel.
100    It maps the function entry points of every function in the kernel API,
101    as well as the addresses of the kernel data structures for the running
102    kernel. Issue the following command to install the map file:</para>
104<screen os="w1"><userinput>cp -v /boot/;</userinput></screen>
106    <para os="x">The kernel configuration file <filename>.config</filename>
107    produced by the <command>make menuconfig</command> step above contains
108    all the configuration selections for the kernel that was just compiled.
109    It is a good idea to keep this file for future reference:</para>
111<screen os="x1"><userinput>cp -v .config /boot/config-&linux-version;</userinput></screen>
113    <para os="y">It is important to note that the files in the kernel source
114    directory are not owned by <systemitem class="username">root</systemitem>.
115    Whenever a package is unpacked as user <systemitem
116    class="username">root</systemitem> (like we do inside the final-system
117    build environment), the files have the user and group IDs of whatever
118    they were on the packager's computer. This is usually not a problem
119    for any other package to be installed because the source tree is
120    removed after the installation. However, the Linux source tree is
121    often retained for a long time. Because of this, there is a chance
122    that whatever user ID the packager used will be assigned to somebody
123    on the machine. That person would then have write access to the kernel
124    source.</para>
126    <para os="y1">If the kernel source tree is going to retained, run
127    <command>chown -R 0:0</command> on the <filename
128    class="directory">linux-&linux-version;</filename> directory to
129    ensure all files are owned by user <systemitem
130    class="username">root</systemitem>.</para>
132    <warning os="z">
133      <para>Some kernel documentation recommends creating a symlink from
134      <filename class="symlink">/usr/src/linux</filename> pointing to the
135      kernel source directory. This is specific to kernels prior to the
136      2.6 series and <emphasis>must not</emphasis> be created on a CLFS
137      system as it can cause problems for packages you may wish to build
138      once your base CLFS system is complete.</para>
140      <para>Also, the headers in the system's <filename
141      class="directory">include</filename> directory should
142      <emphasis>always</emphasis> be the ones against which Glibc was
143      compiled and should <emphasis>never</emphasis> be replaced by headers
144      from a different kernel version.</para>
145    </warning>
147  </sect2>
149  <sect2 id="contents-kernel" role="content">
150    <title>Contents of Linux</title>
152    <segmentedlist>
153      <segtitle>Installed files</segtitle>
155      <seglistitem>
156        <seg>config-[linux-version], clfskernel-[linux-version],
157        and[linux-version]</seg>
158      </seglistitem>
159    </segmentedlist>
161    <variablelist>
162      <bridgehead renderas="sect3">Short Descriptions</bridgehead>
163      <?dbfo list-presentation="list"?>
164      <?dbhtml list-presentation="table"?>
166      <varlistentry id="config">
167        <term><filename>config-[linux-version]</filename></term>
168        <listitem>
169          <para>Contains all the configuration selections for the kernel</para>
170          <indexterm zone="ch-bootable-kernel config">
171            <primary sortas="e-/boot/config">/boot/config-[linux-version]</primary>
172          </indexterm>
173        </listitem>
174      </varlistentry>
176      <varlistentry id="clfskernel">
177        <term><filename>clfskernel-[linux-version]</filename></term>
178        <listitem>
179          <para>The engine of the Linux system. When turning on the
180          computer, the kernel is the first part of the operating system
181          that gets loaded. It detects and initializes all components of
182          the computer's hardware, then makes these components available
183          as a tree of files to the software and turns a single CPU into
184          a multitasking machine capable of running scores of programs
185          seemingly at the same time.</para>
186          <indexterm zone="ch-bootable-kernel clfskernel">
187            <primary sortas="b-clfskernel">clfskernel-[linux-version]</primary>
188          </indexterm>
189        </listitem>
190      </varlistentry>
192      <varlistentry id="">
193        <term><filename>[linux-version]</filename></term>
194        <listitem>
195          <para>A list of addresses and symbols; it maps the entry points
196          and addresses of all the functions and data structures in the
197          kernel</para>
198          <indexterm zone="ch-bootable-kernel">
199            <primary sortas="e-/boot/">/boot/[linux-version]</primary>
200          </indexterm>
201        </listitem>
202      </varlistentry>
204    </variablelist>
206  </sect2>
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