source: chapter10/kernel.xml@ b010eec

multilib
Last change on this file since b010eec was b010eec, checked in by Thomas Trepl (Moody) <thomas@…>, 2 years ago

Automatic merge of trunk into multilib

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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>kernel</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-knl-sbu;</seg>
34 <seg>&linux-knl-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 <para>There are several ways to configure the kernel options. Usually,
58 This is done through a menu-driven interface, for example:</para>
59
60<screen role="nodump"><userinput>make menuconfig</userinput></screen>
61
62 <variablelist>
63 <title>The meaning of optional make environment variables:</title>
64
65 <varlistentry>
66 <term><parameter>LANG=&lt;host_LANG_value&gt; LC_ALL=</parameter></term>
67 <listitem>
68 <para>This establishes the locale setting to the one used on the
69 host. This may be needed for a proper menuconfig ncurses interface
70 line drawing on a UTF-8 linux text console.</para>
71
72 <para>If used, be sure to replace
73 <replaceable>&lt;host_LANG_value&gt;</replaceable> by the value of
74 the <envar>$LANG</envar> variable from your host. You can
75 alternatively use instead the host's value of <envar>$LC_ALL</envar>
76 or <envar>$LC_CTYPE</envar>.</para>
77 </listitem>
78 </varlistentry>
79
80 <varlistentry>
81 <term><command>make menuconfig</command></term>
82 <listitem>
83 <para>This launches an ncurses menu-driven interface. For other
84 (graphical) interfaces, type <command>make help</command>.</para>
85 </listitem>
86 </varlistentry>
87 </variablelist>
88
89 <!-- Support for compiling a keymap into the kernel is deliberately removed -->
90
91 <para>For general information on kernel configuration see <ulink
92 url="&hints-root;kernel-configuration.txt"/>. BLFS has some information
93 regarding particular kernel configuration requirements of packages outside
94 of LFS at <ulink
95 url="&blfs-book;longindex.html#kernel-config-index"/>. Additional
96 information about configuring and building the kernel can be found at
97 <ulink url="http://www.kroah.com/lkn/"/> </para>
98
99 <note>
100 <para>A good starting place for setting up the kernel configuration is to
101 run <command>make defconfig</command>. This will set the base
102 configuration to a good state that takes your current system architecture
103 into account.</para>
104
105 <para>Be sure to enable/disable/set the following features or the system might
106 not work correctly or boot at all:</para>
107
108 <screen role="nodump" revision="sysv">General setup -->
109 &lt; &gt; Enable kernel headers through /sys/kernel/kheaders.tar.xz [CONFIG_IKHEADERS]
110Device Drivers ---&gt;
111 Generic Driver Options ---&gt;
112 [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
113 [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]</screen>
114
115 <screen role="nodump" revision="systemd">General setup -->
116 [ ] Auditing Support [CONFIG_AUDIT]
117 &lt; &gt; Enable kernel headers through /sys/kernel/kheaders.tar.xz [CONFIG_IKHEADERS]
118 [*] Control Group support [CONFIG_CGROUPS]
119 [ ] Enable deprecated sysfs features to support old userspace tools [CONFIG_SYSFS_DEPRECATED]
120 [*] Configure standard kernel features (expert users) [CONFIG_EXPERT] ---&gt;
121 [*] open by fhandle syscalls [CONFIG_FHANDLE]
122Firmware Drivers ---&gt;
123 [*] Export DMI identification via sysfs to userspace [CONFIG_DMIID]
124General architecture-dependent options ---&gt;
125 [*] Enable seccomp to safely compute untrusted bytecode [CONFIG_SECCOMP]
126Networking support ---&gt;
127 Networking options ---&gt;
128 &lt;*&gt; The IPv6 protocol [CONFIG_IPV6]
129Device Drivers ---&gt;
130 Generic Driver Options ---&gt;
131 [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
132 [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]
133 Firmware Loader ---&gt;
134 [ ] Enable the firmware sysfs fallback mechanism [CONFIG_FW_LOADER_USER_HELPER]
135File systems ---&gt;
136 [*] Inotify support for userspace [CONFIG_INOTIFY_USER]
137 Pseudo filesystems ---&gt;
138 [*] Tmpfs POSIX Access Control Lists [CONFIG_TMPFS_POSIX_ACL]</screen>
139 </note>
140
141 <note revision="systemd">
142 <para>While "The IPv6 Protocol" is not strictly
143 required, it is highly recommended by the systemd developers.</para>
144 </note>
145
146 <para revision="sysv">There are several other options that may be desired
147 depending on the requirements for the system. For a list of options needed
148 for BLFS packages, see the <ulink
149 url="&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index">BLFS
150 Index of Kernel Settings</ulink>
151 (&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index).</para>
152
153 <note>
154 <para>If your host hardware is using UEFI and you wish to boot the
155 LFS system with it, you should adjust some kernel configuration
156 following <ulink url="&blfs-book;postlfs/grub-setup.html#uefi-kernel">
157 the BLFS page</ulink>.</para>
158 </note>
159
160 <note arch="ml_32,ml_x32,ml_all">
161 <para>
162 The kernel on a multilib system needs to be able to
163 identify and start binaries compiled for different architectures
164 than the default.
165 </para>
166
167 <para arch="ml_32,ml_all">
168 If support for any 32bit ABI was built, make sure that the option
169 "IA32 Emulation" is selected. The option 'IA32 a.out support' is
170 optional.
171 </para>
172
173 <para arch="ml_x32,ml_all">
174 If support for the x32bit ABI was built, make sure that the option
175 "x32 ABI for 64-bit mode" is selected.
176 </para>
177
178<screen arch="ml_32">Binary Emulations ---&gt;
179 [*] IA32 Emulation [CONFIG_IA32_EMULATION]
180 &lt;M&gt; IA32 a.out support [CONFIG_IA32_AOUT]
181</screen>
182<screen arch="ml_x32">Binary Emulations ---&gt;
183 [*] x32 ABI for 64-bit mode [CONFIG_X86_X32]
184</screen>
185<screen arch="ml_all">Binary Emulations ---&gt;
186 [*] IA32 Emulation [CONFIG_IA32_EMULATION]
187 &lt;M&gt; IA32 a.out support [CONFIG_IA32_AOUT]
188 [*] x32 ABI for 64-bit mode [CONFIG_X86_X32]
189</screen>
190 </note>
191
192 <variablelist>
193 <title>The rationale for the above configuration items:</title>
194
195 <varlistentry>
196 <term>
197 <parameter>
198 Enable kernel headers through /sys/kernel/kheaders.tar.xz
199 </parameter>
200 </term>
201 <listitem>
202 <para>This will require <command>cpio</command> building the kernel.
203 <command>cpio</command> is not installed by LFS.</para>
204 </listitem>
205 </varlistentry>
206
207 <varlistentry>
208 <term><parameter>Support for uevent helper</parameter></term>
209 <listitem>
210 <para>Having this option set may interfere with device
211 management when using Udev/Eudev. </para>
212 </listitem>
213 </varlistentry>
214
215 <varlistentry>
216 <term><parameter>Maintain a devtmpfs</parameter></term>
217 <listitem>
218 <para>This will create automated device nodes which are populated by the
219 kernel, even without Udev running. Udev then runs on top of this,
220 managing permissions and adding symlinks. This configuration
221 item is required for all users of Udev/Eudev.</para>
222 </listitem>
223 </varlistentry>
224
225 </variablelist>
226
227 <para>Alternatively, <command>make oldconfig</command> may be more
228 appropriate in some situations. See the <filename>README</filename>
229 file for more information.</para>
230
231 <para>If desired, skip kernel configuration by copying the kernel
232 config file, <filename>.config</filename>, from the host system
233 (assuming it is available) to the unpacked <filename
234 class="directory">linux-&linux-version;</filename> directory. However,
235 we do not recommend this option. It is often better to explore all the
236 configuration menus and create the kernel configuration from
237 scratch.</para>
238
239 <para>Compile the kernel image and modules:</para>
240
241<screen><userinput remap="make">make</userinput></screen>
242
243 <para>If using kernel modules, module configuration in <filename
244 class="directory">/etc/modprobe.d</filename> may be required.
245 Information pertaining to modules and kernel configuration is
246 located in <xref linkend="ch-config-udev"/> and in the kernel
247 documentation in the <filename
248 class="directory">linux-&linux-version;/Documentation</filename> directory.
249 Also, <filename>modprobe.d(5)</filename> may be of interest.</para>
250
251 <para>Unless module support has been disabled in the kernel configuration,
252 install the modules with:</para>
253
254<screen><userinput remap="install">make modules_install</userinput></screen>
255
256 <para>After kernel compilation is complete, additional steps are
257 required to complete the installation. Some files need to be copied to
258 the <filename class="directory">/boot</filename> directory.</para>
259
260 <caution>
261 <para>If the host system has a separate /boot partition, the files copied
262 below should go there. The easiest way to do that is to bind /boot on the
263 host (outside chroot) to /mnt/lfs/boot before proceeding. As the root
264 user in the <emphasis>host system</emphasis>:</para>
265
266<screen role="nodump"><userinput>mount --bind /boot /mnt/lfs/boot</userinput></screen>
267 </caution>
268
269 <para>The path to the kernel image may vary depending on the platform being
270 used. The filename below can be changed to suit your taste, but the stem of
271 the filename should be <emphasis>vmlinuz</emphasis> to be compatible with
272 the automatic setup of the boot process described in the next section. The
273 following command assumes an x86 architecture:</para>
274
275<screen><userinput remap="install">cp -iv arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
276
277 <para><filename>System.map</filename> is a symbol file for the kernel.
278 It maps the function entry points of every function in the kernel API,
279 as well as the addresses of the kernel data structures for the running
280 kernel. It is used as a resource when investigating kernel problems.
281 Issue the following command to install the map file:</para>
282
283<screen><userinput remap="install">cp -iv System.map /boot/System.map-&linux-version;</userinput></screen>
284
285 <para>The kernel configuration file <filename>.config</filename>
286 produced by the <command>make menuconfig</command> step
287 above contains all the configuration selections for the kernel
288 that was just compiled. It is a good idea to keep this file for future
289 reference:</para>
290
291<screen><userinput remap="install">cp -iv .config /boot/config-&linux-version;</userinput></screen>
292
293 <para>Install the documentation for the Linux kernel:</para>
294
295<screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
296cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
297
298 <para>It is important to note that the files in the kernel source
299 directory are not owned by <emphasis>root</emphasis>. Whenever a
300 package is unpacked as user <emphasis>root</emphasis> (like we did
301 inside chroot), the files have the user and group IDs of whatever
302 they were on the packager's computer. This is usually not a problem
303 for any other package to be installed because the source tree is
304 removed after the installation. However, the Linux source tree is
305 often retained for a long time. Because of this, there is a chance
306 that whatever user ID the packager used will be assigned to somebody
307 on the machine. That person would then have write access to the kernel
308 source.</para>
309
310 <note>
311 <para>In many cases, the configuration of the kernel will need to be
312 updated for packages that will be installed later in BLFS. Unlike
313 other packages, it is not necessary to remove the kernel source tree
314 after the newly built kernel is installed.</para>
315
316 <para>If the kernel source tree is going to be retained, run
317 <command>chown -R 0:0</command> on the <filename
318 class="directory">linux-&linux-version;</filename> directory to ensure
319 all files are owned by user <emphasis>root</emphasis>.</para>
320 </note>
321
322 <warning>
323 <para>Some kernel documentation recommends creating a symlink from
324 <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
325 source directory. This is specific to kernels prior to the 2.6 series and
326 <emphasis>must not</emphasis> be created on an LFS system as it can cause
327 problems for packages you may wish to build once your base LFS system is
328 complete.</para>
329 </warning>
330
331 <warning>
332 <para>The headers in the system's <filename
333 class="directory">include</filename> directory (<filename
334 class="directory">/usr/include</filename>) should
335 <emphasis>always</emphasis> be the ones against which Glibc was compiled,
336 that is, the sanitised headers installed in <xref
337 linkend="ch-tools-linux-headers"/>. Therefore, they should
338 <emphasis>never</emphasis> be replaced by either the raw kernel headers
339 or any other kernel sanitized headers.</para>
340 </warning>
341
342 </sect2>
343
344 <sect2 id="conf-modprobe" role="configuration">
345 <title>Configuring Linux Module Load Order</title>
346
347 <indexterm zone="conf-modprobe">
348 <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
349 </indexterm>
350
351 <para>Most of the time Linux modules are loaded automatically, but
352 sometimes it needs some specific direction. The program that loads
353 modules, <command>modprobe</command> or <command>insmod</command>, uses
354 <filename>/etc/modprobe.d/usb.conf</filename> for this purpose. This file
355 needs to be created so that if the USB drivers (ehci_hcd, ohci_hcd and
356 uhci_hcd) have been built as modules, they will be loaded in the correct
357 order; ehci_hcd needs to be loaded prior to ohci_hcd and uhci_hcd in order
358 to avoid a warning being output at boot time.</para>
359
360 <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
361 the following:</para>
362
363<screen><userinput>install -v -m755 -d /etc/modprobe.d
364cat &gt; /etc/modprobe.d/usb.conf &lt;&lt; "EOF"
365<literal># Begin /etc/modprobe.d/usb.conf
366
367install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
368install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
369
370# End /etc/modprobe.d/usb.conf</literal>
371EOF</userinput></screen>
372
373 </sect2>
374
375 <sect2 id="contents-kernel" role="content">
376 <title>Contents of Linux</title>
377
378 <segmentedlist>
379 <segtitle>Installed files</segtitle>
380 <segtitle>Installed directories</segtitle>
381
382 <seglistitem>
383 <seg>config-&linux-version;,
384 vmlinuz-&linux-version;-lfs-&version;,
385 and System.map-&linux-version;</seg>
386 <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
387 </seglistitem>
388 </segmentedlist>
389
390 <variablelist>
391 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
392 <?dbfo list-presentation="list"?>
393 <?dbhtml list-presentation="table"?>
394
395 <varlistentry id="config">
396 <term><filename>config-&linux-version;</filename></term>
397 <listitem>
398 <para>Contains all the configuration selections for the kernel</para>
399 <indexterm zone="ch-bootable-kernel config">
400 <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
401 </indexterm>
402 </listitem>
403 </varlistentry>
404
405 <varlistentry id="lfskernel">
406 <term><filename>vmlinuz-&linux-version;-lfs-&version;</filename></term>
407 <listitem>
408 <para>The engine of the Linux system. When turning on the computer,
409 the kernel is the first part of the operating system that gets loaded.
410 It detects and initializes all components of the computer's hardware,
411 then makes these components available as a tree of files to the
412 software and turns a single CPU into a multitasking machine capable
413 of running scores of programs seemingly at the same time</para>
414 <indexterm zone="ch-bootable-kernel lfskernel">
415 <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
416 </indexterm>
417 </listitem>
418 </varlistentry>
419
420 <varlistentry id="System.map">
421 <term><filename>System.map-&linux-version;</filename></term>
422 <listitem>
423 <para>A list of addresses and symbols; it maps the entry points and
424 addresses of all the functions and data structures in the
425 kernel</para>
426 <indexterm zone="ch-bootable-kernel System.map">
427 <primary sortas="e-/boot/System.map">/boot/System.map-&linux-version;</primary>
428 </indexterm>
429 </listitem>
430 </varlistentry>
431
432 </variablelist>
433
434 </sect2>
435
436</sect1>
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