source: bootable/x86/kernel.xml @ e1e8f31

Last change on this file since e1e8f31 was e1e8f31, checked in by Jim Gifford <clfs@…>, 17 years ago

r1091@server (orig r1089): chris | 2006-01-22 09:24:18 -0800
Added note about to kernel config about the bootscripts

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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
3  "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
4  <!ENTITY % general-entities SYSTEM "../../general.ent">
5  %general-entities;
6]>
7
8<sect1 id="ch-bootable-kernel" role="wrap">
9  <?dbhtml filename="kernel.html"?>
10
11  <title>Linux-&linux-version;</title>
12
13  <indexterm zone="ch-bootable-kernel">
14    <primary sortas="a-Linux">Linux</primary>
15  </indexterm>
16
17  <sect2 role="package"><title/>
18    <para>The Linux package contains the Linux kernel.</para>
19
20    <segmentedlist>
21      <segtitle>&dependencies;</segtitle>
22
23      <seglistitem>
24        <seg>Bash, Binutils, Coreutils, Findutils, GCC, Glibc, Grep,
25        Gzip, Kbd, Make, Module-Init-Tools, Perl, and Sed</seg>
26      </seglistitem>
27    </segmentedlist>
28
29  </sect2>
30
31  <sect2 role="installation">
32    <title>Installation of the kernel</title>
33
34    <para os="a">Building the kernel involves a few steps&mdash;configuration,
35    compilation, and installation. Read the <filename>README</filename>
36    file in the kernel source tree for alternative methods to the way this
37    book configures the kernel.</para>
38
39    <para os="b">Prepare for compilation by running the following command:</para>
40
41<screen os="c"><userinput>make mrproper</userinput></screen>
42
43    <para os="d">This ensures that the kernel tree is absolutely clean. The
44    kernel team recommends that this command be issued prior to each
45    kernel compilation. Do not rely on the source tree being clean after
46    un-tarring.</para>
47
48    <para os="e">If, in <xref linkend="ch-scripts-console" role=","/> it was
49    decided to compile the keymap into the kernel, issue the command
50    below:</para>
51
52<screen os="f"><userinput>loadkeys -m /usr/share/kbd/keymaps/<replaceable>[path to  keymap]</replaceable> &gt; \
53    drivers/char/defkeymap.c</userinput></screen>
54
55    <para os="g">For example, if using a Dutch keyboard, use
56    <filename>/usr/share/kbd/keymaps/i386/qwerty/nl.map.gz</filename>.</para>
57
58    <para os="h">Configure the kernel via a menu-driven interface.
59    Please note that the udev bootscript requires "rtc" and "tmpfs" to be
60    enabled and built into the kernel, not as modules. BLFS has
61    some information regarding particular kernel configuration requirements of
62    packages outside of LFS at <ulink
63    url="&blfs-root;view/svn/longindex.html#kernel-config-index"/>:</para>
64
65<screen os="i"><userinput>make menuconfig</userinput></screen>
66
67    <para os="j">Alternatively, <command>make oldconfig</command> may be more
68    appropriate in some situations. See the <filename>README</filename>
69    file for more information.</para>
70
71    <para os="k">If desired, skip kernel configuration by copying the kernel
72    config file, <filename>.config</filename>, from the host system
73    (assuming it is available) to the root directory of the unpacked kernel
74    sources. However, we do not recommend this option. It is often better
75    to explore all the configuration menus and create the kernel configuration
76    from scratch.</para>
77
78    <note os="l">
79      <para>Linux-2.6 kernel series is required to be compiled with GCC-3.x or
80      later, in this case &gcc-version;. It is not recommended to compile the
81      kernel with GCC-2.95.x, as this causes failures in the Glibc test suite.
82      Normally, this wouldn't be mentioned as LFS doesn't build GCC-2.95.x.
83      Unfortunately, the kernel documentation is outdated and still claims
84      GCC-2.95.3 is the recommended compiler.</para>
85    </note>
86
87    <para os="m">Compile the kernel image and modules:</para>
88
89<screen os="n"><userinput>make</userinput></screen>
90
91    <para os="o">If using kernel modules, an
92    <filename>/etc/modprobe.conf</filename> file may be needed.
93    Information pertaining to modules and kernel configuration is
94    located in the kernel documentation in the <filename
95    class="directory">Documentation</filename> directory of the kernel
96    sources tree. Also, <filename>modprobe.conf(5)</filename> may
97    be of interest.</para>
98
99    <para os="p">Be very careful when reading other documentation relating to
100    kernel modules because it usually applies to 2.4.x kernels only. As
101    far as we know, kernel configuration issues specific to Hotplug and
102    Udev are not documented. The problem is that Udev will create a device
103    node only if Hotplug or a user-written script inserts the corresponding
104    module into the kernel, and not all modules are detectable by Hotplug.
105    Note that statements like the one below in the
106    <filename>/etc/modprobe.conf</filename> file do not work with Udev:</para>
107
108<screen os="q"><literal>alias char-major-XXX some-module</literal></screen>
109
110    <para os="r">Because of the complications with Hotplug, Udev, and modules,
111    we strongly recommend starting with a completely non-modular kernel
112    configuration, especially if this is the first time using Udev.</para>
113
114    <para os="s">Install the modules, if the kernel configuration uses
115    them:</para>
116
117<screen os="t"><userinput>make modules_install</userinput></screen>
118
119    <para os="u">After kernel compilation is complete, additional steps are
120    required to complete the installation. Some files need to be copied to
121    the <filename class="directory">/boot</filename> directory.</para>
122
123    <para os="v">Issue the following command to install the kernel:</para>
124
125<screen><userinput>cp arch/i386/boot/bzImage /boot/lfskernel-&linux-version;</userinput></screen>
126
127    <para os="w"><filename>System.map</filename> is a symbol file for the kernel.
128    It maps the function entry points of every function in the kernel API,
129    as well as the addresses of the kernel data structures for the running
130    kernel. Issue the following command to install the map file:</para>
131
132<screen os="w1"><userinput>cp System.map /boot/System.map-&linux-version;</userinput></screen>
133
134    <para os="x">The kernel configuration file <filename>.config</filename>
135    produced by the <command>make menuconfig</command> step above contains
136    all the configuration selections for the kernel that was just compiled.
137    It is a good idea to keep this file for future reference:</para>
138
139<screen os="x1"><userinput>cp .config /boot/config-&linux-version;</userinput></screen>
140
141    <para os="y">It is important to note that the files in the kernel source
142    directory are not owned by <systemitem class="username">root</systemitem>.
143    Whenever a package is unpacked as user <systemitem
144    class="username">root</systemitem> (like we did
145    inside chroot), the files have the user and group IDs of whatever
146    they were on the packager's computer. This is usually not a problem
147    for any other package to be installed because the source tree is
148    removed after the installation. However, the Linux source tree is
149    often retained for a long time.  Because of this, there is a chance
150    that whatever user ID the packager used will be assigned to somebody
151    on the machine. That person would then have write access to the kernel
152    source.</para>
153
154    <para os="y1">If the kernel source tree is going to retained, run
155    <command>chown -R 0:0</command> on the <filename
156    class="directory">linux-&linux-version;</filename> directory to
157    ensure all files are owned by user <systemitem
158    class="username">root</systemitem>.</para>
159
160    <warning os="z">
161      <para>Some kernel documentation recommends creating a symlink from
162      <filename class="symlink">/usr/src/linux</filename> pointing to the
163      kernel source directory. This is specific to kernels prior to the
164      2.6 series and <emphasis>must not</emphasis> be created on an LFS
165      system as it can cause problems for packages you may wish to build
166      once your base LFS system is complete.</para>
167
168      <para>Also, the headers in the system's <filename
169      class="directory">include</filename> directory should
170      <emphasis>always</emphasis> be the ones against which Glibc was
171      compiled, that is, the ones from the Linux-Libc-Headers package,
172      and therefore, should <emphasis>never</emphasis> be replaced by
173      the kernel headers.</para>
174    </warning>
175
176  </sect2>
177
178  <sect2 id="contents-kernel" role="content">
179    <title>Contents of Linux</title>
180
181    <segmentedlist>
182      <segtitle>Installed files</segtitle>
183
184      <seglistitem>
185        <seg>config-[linux-version], lfskernel-[linux-version],
186        and System.map-[linux-version]</seg>
187      </seglistitem>
188    </segmentedlist>
189
190    <variablelist>
191      <bridgehead renderas="sect3">Short Descriptions</bridgehead>
192      <?dbfo list-presentation="list"?>
193      <?dbhtml list-presentation="table"?>
194
195      <varlistentry id="config">
196        <term><filename>config-[linux-version]</filename></term>
197        <listitem>
198          <para>Contains all the configuration selections for the kernel</para>
199          <indexterm zone="ch-bootable-kernel config">
200            <primary sortas="e-/boot/config">/boot/config-[linux-version]</primary>
201          </indexterm>
202        </listitem>
203      </varlistentry>
204
205      <varlistentry id="lfskernel">
206        <term><filename>lfskernel-[linux-version]</filename></term>
207        <listitem>
208          <para>The engine of the Linux system. When turning on the
209          computer, the kernel is the first part of the operating system
210          that gets loaded. It detects and initializes all components of
211          the computer's hardware, then makes these components available
212          as a tree of files to the software and turns a single CPU into
213          a multitasking machine capable of running scores of programs
214          seemingly at the same time.</para>
215          <indexterm zone="ch-bootable-kernel lfskernel">
216            <primary sortas="b-lfskernel">lfskernel-[linux-version]</primary>
217          </indexterm>
218        </listitem>
219      </varlistentry>
220
221      <varlistentry id="System.map">
222        <term><filename>System.map-[linux-version]</filename></term>
223        <listitem>
224          <para>A list of addresses and symbols; it maps the entry points
225          and addresses of all the functions and data structures in the
226          kernel</para>
227          <indexterm zone="ch-bootable-kernel System.map">
228            <primary sortas="e-/boot/System.map">/boot/System.map-[linux-version]</primary>
229          </indexterm>
230        </listitem>
231      </varlistentry>
232
233    </variablelist>
234
235  </sect2>
236
237</sect1>
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