source: chapter08/kernel.xml@ 764b5cf

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Last change on this file since 764b5cf was 764b5cf, checked in by Bruce Dubbs <bdubbs@…>, 15 years ago

Add a reference to the kernel-configuration hint

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@8939 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

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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 "http://www.oasis-open.org/docbook/xml/4.5/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 <sect1info condition="script">
12 <productname>linux</productname>
13 <productnumber>&linux-version;</productnumber>
14 <address>&linux-url;</address>
15 </sect1info>
16
17 <title>Linux-&linux-version;</title>
18
19 <indexterm zone="ch-bootable-kernel">
20 <primary sortas="a-Linux">Linux</primary>
21 </indexterm>
22
23 <sect2 role="package">
24 <title/>
25
26 <para>The Linux package contains the Linux kernel.</para>
27
28 <segmentedlist>
29 <segtitle>&buildtime;</segtitle>
30 <segtitle>&diskspace;</segtitle>
31
32 <seglistitem>
33 <seg>&linux-ch8-sbu;</seg>
34 <seg>&linux-ch8-du;</seg>
35 </seglistitem>
36 </segmentedlist>
37
38 </sect2>
39
40 <sect2 role="installation">
41 <title>Installation of the kernel</title>
42
43 <para>Building the kernel involves a few steps&mdash;configuration,
44 compilation, and installation. Read the <filename>README</filename> file
45 in the kernel source tree for alternative methods to the way this book
46 configures the kernel.</para>
47
48 <para>Prepare for compilation by running the following command:</para>
49
50<screen><userinput remap="pre">make mrproper</userinput></screen>
51
52 <para>This ensures that the kernel tree is absolutely clean. The
53 kernel team recommends that this command be issued prior to each
54 kernel compilation. Do not rely on the source tree being clean after
55 un-tarring.</para>
56
57 <!-- Support for compiling a keymap into the kernel is deliberately removed -->
58
59 <para>Configure the kernel via a menu-driven interface. For general
60 information on kernel configuration see <ulink
61 url="&hints-root;kernel-configuration.txt"/>. BLFS has some information
62 regarding particular kernel configuration requirements of packages outside
63 of LFS at <ulink
64 url="&blfs-root;view/svn/longindex.html#kernel-config-index"/>:</para>
65
66<screen role="nodump"><userinput>make LANG=<replaceable>&lt;host_LANG_value&gt;</replaceable> LC_ALL= menuconfig</userinput></screen>
67
68 <variablelist>
69 <title>The meaning of the make parameters:</title>
70
71 <varlistentry>
72 <term><parameter>LANG=&lt;host_LANG_value&gt; LC_ALL=</parameter></term>
73 <listitem>
74 <para>This establishes the locale setting to the one used on the host.
75 This is needed for a proper menuconfig ncurses interface line
76 drawing on UTF-8 linux text console.</para>
77
78 <para>Be sure to replace <replaceable>&lt;host_LANG_value&gt;</replaceable>
79 by the value of the <envar>$LANG</envar> variable from your host.
80 If not set, you could use instead the host's value of <envar>$LC_ALL</envar>
81 or <envar>$LC_CTYPE</envar>.</para>
82 </listitem>
83 </varlistentry>
84
85 </variablelist>
86
87 <para>Alternatively, <command>make oldconfig</command> may be more
88 appropriate in some situations. See the <filename>README</filename>
89 file for more information.</para>
90
91 <para>If desired, skip kernel configuration by copying the kernel
92 config file, <filename>.config</filename>, from the host system
93 (assuming it is available) to the unpacked <filename
94 class="directory">linux-&linux-version;</filename> directory. However,
95 we do not recommend this option. It is often better to explore all the
96 configuration menus and create the kernel configuration from
97 scratch.</para>
98
99 <para>Compile the kernel image and modules:</para>
100
101<screen><userinput remap="make">make</userinput></screen>
102
103 <para>If using kernel modules, an <filename>/etc/modprobe.conf</filename>
104 file may be needed. Information pertaining to modules and kernel
105 configuration is located in <xref linkend="ch-scripts-udev"/> and in the
106 kernel documentation in the <filename
107 class="directory">linux-&linux-version;/Documentation</filename> directory.
108 Also, <filename>modprobe.conf(5)</filename> may be of interest.</para>
109
110 <para>Install the modules, if the kernel configuration uses them:</para>
111
112<screen><userinput remap="install">make modules_install</userinput></screen>
113
114 <para>After kernel compilation is complete, additional steps are
115 required to complete the installation. Some files need to be copied to
116 the <filename class="directory">/boot</filename> directory.</para>
117
118 <para>The path to the kernel image may vary depending on the platform
119 being used. The following command assumes an x86 architecture:</para>
120
121<screen><userinput remap="install">cp -v arch/x86/boot/bzImage /boot/lfskernel-&linux-version;</userinput></screen>
122
123 <para><filename>System.map</filename> is a symbol file for the kernel.
124 It maps the function entry points of every function in the kernel API,
125 as well as the addresses of the kernel data structures for the running
126 kernel. Issue the following command to install the map file:</para>
127
128<screen><userinput remap="install">cp -v System.map /boot/System.map-&linux-version;</userinput></screen>
129
130 <para>The kernel configuration file <filename>.config</filename>
131 produced by the <command>make menuconfig</command> step
132 above contains all the configuration selections for the kernel
133 that was just compiled. It is a good idea to keep this file for future
134 reference:</para>
135
136<screen><userinput remap="install">cp -v .config /boot/config-&linux-version;</userinput></screen>
137
138 <para>Install the documentation for the Linux kernel:</para>
139
140<screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
141cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
142
143 <para>It is important to note that the files in the kernel source
144 directory are not owned by <emphasis>root</emphasis>. Whenever a
145 package is unpacked as user <emphasis>root</emphasis> (like we did
146 inside chroot), the files have the user and group IDs of whatever
147 they were on the packager's computer. This is usually not a problem
148 for any other package to be installed because the source tree is
149 removed after the installation. However, the Linux source tree is
150 often retained for a long time. Because of this, there is a chance
151 that whatever user ID the packager used will be assigned to somebody
152 on the machine. That person would then have write access to the kernel
153 source.</para>
154
155 <para>If the kernel source tree is going to be retained, run
156 <command>chown -R 0:0</command> on the <filename
157 class="directory">linux-&linux-version;</filename> directory to ensure
158 all files are owned by user <emphasis>root</emphasis>.</para>
159
160 <warning>
161 <para>Some kernel documentation recommends creating a symlink from
162 <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
163 source directory. This is specific to kernels prior to the 2.6 series and
164 <emphasis>must not</emphasis> be created on an LFS system as it can cause
165 problems for packages you may wish to build once your base LFS system is
166 complete.</para>
167 </warning>
168
169 <warning>
170 <para>The headers in the system's
171 <filename class="directory">include</filename> directory should
172 <emphasis>always</emphasis> be the ones against which Glibc was compiled,
173 that is, the sanitised headers from this Linux kernel tarball.
174 Therefore, they should <emphasis>never</emphasis> be replaced by either
175 the raw kernel headers or any other kernel sanitized headers.</para>
176 </warning>
177
178 </sect2>
179
180 <sect2 id="conf-modprobe" role="configuration">
181 <title>Configuring Linux Module Load Order</title>
182
183 <indexterm zone="conf-modprobe">
184 <primary sortas="e-/etc/modprobe.conf">/etc/modprobe.conf</primary>
185 </indexterm>
186
187 <para>The <filename>/etc/modprobe.conf</filename> file needs to be created
188 so that if the USB drivers (ehci_hcd, ohci_hcd and uhci_hcd) have been built
189 as modules, they will be loaded in the correct order; ehci_hcd needs to be
190 loaded prior to ohci_hcd and uhci_hcd in order to avoid a warning being
191 output at boot time.</para>
192
193 <para>Create a new file <filename>/etc/modprobe.conf</filename> by running
194 the following:</para>
195
196<screen><userinput>cat &gt; /etc/modprobe.conf &lt;&lt; "EOF"
197<literal># Begin /etc/modprobe.conf
198
199install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
200install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
201
202# End /etc/modprobe.conf</literal>
203EOF</userinput></screen>
204
205 </sect2>
206
207 <sect2 id="contents-kernel" role="content">
208 <title>Contents of Linux</title>
209
210 <segmentedlist>
211 <segtitle>Installed files</segtitle>
212
213 <seglistitem>
214 <seg>config-&linux-version;, lfskernel-&linux-version;, and
215 System.map-&linux-version;</seg>
216 </seglistitem>
217 </segmentedlist>
218
219 <variablelist>
220 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
221 <?dbfo list-presentation="list"?>
222 <?dbhtml list-presentation="table"?>
223
224 <varlistentry id="config">
225 <term><filename>config-&linux-version;</filename></term>
226 <listitem>
227 <para>Contains all the configuration selections for the kernel</para>
228 <indexterm zone="ch-bootable-kernel config">
229 <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
230 </indexterm>
231 </listitem>
232 </varlistentry>
233
234 <varlistentry id="lfskernel">
235 <term><filename>lfskernel-&linux-version;</filename></term>
236 <listitem>
237 <para>The engine of the Linux system. When turning on the computer,
238 the kernel is the first part of the operating system that gets loaded.
239 It detects and initializes all components of the computer's hardware,
240 then makes these components available as a tree of files to the
241 software and turns a single CPU into a multitasking machine capable
242 of running scores of programs seemingly at the same time</para>
243 <indexterm zone="ch-bootable-kernel lfskernel">
244 <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
245 </indexterm>
246 </listitem>
247 </varlistentry>
248
249 <varlistentry id="System.map">
250 <term><filename>System.map-&linux-version;</filename></term>
251 <listitem>
252 <para>A list of addresses and symbols; it maps the entry points and
253 addresses of all the functions and data structures in the
254 kernel</para>
255 <indexterm zone="ch-bootable-kernel System.map">
256 <primary sortas="e-/boot/System.map">/boot/System.map-&linux-version;</primary>
257 </indexterm>
258 </listitem>
259 </varlistentry>
260
261 </variablelist>
262
263 </sect2>
264
265</sect1>
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