source: chapter10/kernel.xml@ 3a72ffa

multilib
Last change on this file since 3a72ffa was 65ac2fd, 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 Graphics support ---&gt;
112 Frame buffer Devices ---&gt;
113 [*] Support for frame buffer devices ----
114 Generic Driver Options ---&gt;
115 [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
116 [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]
117 [*] Automount devtmpfs at /dev, after the kernel mounted the rootfs [CONFIG_DEVTMPFS_MOUNT]</screen>
118
119 <screen role="nodump" revision="systemd">General setup -->
120 [ ] Auditing Support [CONFIG_AUDIT]
121 CPU/Task time and stats accounting ---&gt;
122 [*] Pressure stall information tracking [CONFIG_PSI]
123 &lt; &gt; Enable kernel headers through /sys/kernel/kheaders.tar.xz [CONFIG_IKHEADERS]
124 [*] Control Group support [CONFIG_CGROUPS] ---&gt;
125 [*] Memory controller [CONFIG_MEMCG]
126 [ ] Enable deprecated sysfs features to support old userspace tools [CONFIG_SYSFS_DEPRECATED]
127 [*] Configure standard kernel features (expert users) [CONFIG_EXPERT] ---&gt;
128 [*] open by fhandle syscalls [CONFIG_FHANDLE]
129General architecture-dependent options ---&gt;
130 [*] Enable seccomp to safely compute untrusted bytecode [CONFIG_SECCOMP]
131Networking support ---&gt;
132 Networking options ---&gt;
133 &lt;*&gt; The IPv6 protocol [CONFIG_IPV6]
134Device Drivers ---&gt;
135 Generic Driver Options ---&gt;
136 [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
137 [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]
138 [*] Automount devtmpfs at /dev, after the kernel mounted the rootfs [CONFIG_DEVTMPFS_MOUNT]
139 Firmware Loader ---&gt;
140 [ ] Enable the firmware sysfs fallback mechanism [CONFIG_FW_LOADER_USER_HELPER]
141 Firmware Drivers ---&gt;
142 [*] Export DMI identification via sysfs to userspace [CONFIG_DMIID]
143 Graphics support ---&gt;
144 Frame buffer Devices ---&gt;
145 &lt;*&gt; Support for frame buffer devices ---&gt;
146File systems ---&gt;
147 [*] Inotify support for userspace [CONFIG_INOTIFY_USER]
148 Pseudo filesystems ---&gt;
149 [*] Tmpfs POSIX Access Control Lists [CONFIG_TMPFS_POSIX_ACL]</screen>
150 </note>
151
152 <note revision="systemd">
153 <para>While "The IPv6 Protocol" is not strictly
154 required, it is highly recommended by the systemd developers.</para>
155 </note>
156
157 <para revision="sysv">There are several other options that may be desired
158 depending on the requirements for the system. For a list of options needed
159 for BLFS packages, see the <ulink
160 url="&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index">BLFS
161 Index of Kernel Settings</ulink>
162 (&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index).</para>
163
164 <note>
165 <para>If your host hardware is using UEFI and you wish to boot the
166 LFS system with it, you should adjust some kernel configuration
167 following <ulink url="&blfs-book;postlfs/grub-setup.html#uefi-kernel">
168 the BLFS page</ulink>.</para>
169 </note>
170
171 <note arch="ml_32,ml_x32,ml_all">
172 <para>
173 The kernel on a multilib system needs to be able to
174 identify and start binaries compiled for different architectures
175 than the default.
176 </para>
177
178 <para arch="ml_32,ml_all">
179 If support for any 32bit ABI was built, make sure that the option
180 "IA32 Emulation" is selected. The option 'IA32 a.out support' is
181 optional.
182 </para>
183
184 <para arch="ml_x32,ml_all">
185 If support for the x32bit ABI was built, make sure that the option
186 "x32 ABI for 64-bit mode" is selected.
187 </para>
188
189<screen arch="ml_32">Binary Emulations ---&gt;
190 [*] IA32 Emulation [CONFIG_IA32_EMULATION]
191 &lt;M&gt; IA32 a.out support [CONFIG_IA32_AOUT]
192</screen>
193<screen arch="ml_x32">Binary Emulations ---&gt;
194 [*] x32 ABI for 64-bit mode [CONFIG_X86_X32]
195</screen>
196<screen arch="ml_all">Binary Emulations ---&gt;
197 [*] IA32 Emulation [CONFIG_IA32_EMULATION]
198 &lt;M&gt; IA32 a.out support [CONFIG_IA32_AOUT]
199 [*] x32 ABI for 64-bit mode [CONFIG_X86_X32]
200</screen>
201 </note>
202
203 <variablelist>
204 <title>The rationale for the above configuration items:</title>
205
206 <varlistentry>
207 <term>
208 <parameter>
209 Enable kernel headers through /sys/kernel/kheaders.tar.xz
210 </parameter>
211 </term>
212 <listitem>
213 <para>This will require <command>cpio</command> building the kernel.
214 <command>cpio</command> is not installed by LFS.</para>
215 </listitem>
216 </varlistentry>
217
218 <varlistentry>
219 <term><parameter>Support for uevent helper</parameter></term>
220 <listitem>
221 <para>Having this option set may interfere with device
222 management when using Udev/Eudev. </para>
223 </listitem>
224 </varlistentry>
225
226 <varlistentry>
227 <term><parameter>Maintain a devtmpfs</parameter></term>
228 <listitem>
229 <para>This will create automated device nodes which are populated by the
230 kernel, even without Udev running. Udev then runs on top of this,
231 managing permissions and adding symlinks. This configuration
232 item is required for all users of Udev/Eudev.</para>
233 </listitem>
234 </varlistentry>
235
236 <varlistentry>
237 <term><parameter>Automount devtmpfs at /dev</parameter></term>
238 <listitem>
239 <para>This will mount the kernel view of the devices on /dev
240 upon switching to root filesystem just before starting
241 init.</para>
242 </listitem>
243 </varlistentry>
244
245 </variablelist>
246
247 <para>Alternatively, <command>make oldconfig</command> may be more
248 appropriate in some situations. See the <filename>README</filename>
249 file for more information.</para>
250
251 <para>If desired, skip kernel configuration by copying the kernel
252 config file, <filename>.config</filename>, from the host system
253 (assuming it is available) to the unpacked <filename
254 class="directory">linux-&linux-version;</filename> directory. However,
255 we do not recommend this option. It is often better to explore all the
256 configuration menus and create the kernel configuration from
257 scratch.</para>
258
259 <para>Compile the kernel image and modules:</para>
260
261<screen><userinput remap="make">make</userinput></screen>
262
263 <para>If using kernel modules, module configuration in <filename
264 class="directory">/etc/modprobe.d</filename> may be required.
265 Information pertaining to modules and kernel configuration is
266 located in <xref linkend="ch-config-udev"/> and in the kernel
267 documentation in the <filename
268 class="directory">linux-&linux-version;/Documentation</filename> directory.
269 Also, <filename>modprobe.d(5)</filename> may be of interest.</para>
270
271 <para>Unless module support has been disabled in the kernel configuration,
272 install the modules with:</para>
273
274<screen><userinput remap="install">make modules_install</userinput></screen>
275
276 <para>After kernel compilation is complete, additional steps are
277 required to complete the installation. Some files need to be copied to
278 the <filename class="directory">/boot</filename> directory.</para>
279
280 <caution>
281 <para>If the host system has a separate /boot partition, the files copied
282 below should go there. The easiest way to do that is to bind /boot on the
283 host (outside chroot) to /mnt/lfs/boot before proceeding. As the
284 &root; user in the <emphasis>host system</emphasis>:</para>
285
286<screen role="nodump"><userinput>mount --bind /boot /mnt/lfs/boot</userinput></screen>
287 </caution>
288
289 <para>The path to the kernel image may vary depending on the platform being
290 used. The filename below can be changed to suit your taste, but the stem of
291 the filename should be <emphasis>vmlinuz</emphasis> to be compatible with
292 the automatic setup of the boot process described in the next section. The
293 following command assumes an x86 architecture:</para>
294
295<screen><userinput remap="install">cp -iv arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
296
297 <para><filename>System.map</filename> is a symbol file for the kernel.
298 It maps the function entry points of every function in the kernel API,
299 as well as the addresses of the kernel data structures for the running
300 kernel. It is used as a resource when investigating kernel problems.
301 Issue the following command to install the map file:</para>
302
303<screen><userinput remap="install">cp -iv System.map /boot/System.map-&linux-version;</userinput></screen>
304
305 <para>The kernel configuration file <filename>.config</filename>
306 produced by the <command>make menuconfig</command> step
307 above contains all the configuration selections for the kernel
308 that was just compiled. It is a good idea to keep this file for future
309 reference:</para>
310
311<screen><userinput remap="install">cp -iv .config /boot/config-&linux-version;</userinput></screen>
312
313 <para>Install the documentation for the Linux kernel:</para>
314
315<screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
316cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
317
318 <para>It is important to note that the files in the kernel source
319 directory are not owned by <emphasis>root</emphasis>. Whenever a
320 package is unpacked as user <emphasis>root</emphasis> (like we did
321 inside chroot), the files have the user and group IDs of whatever
322 they were on the packager's computer. This is usually not a problem
323 for any other package to be installed because the source tree is
324 removed after the installation. However, the Linux source tree is
325 often retained for a long time. Because of this, there is a chance
326 that whatever user ID the packager used will be assigned to somebody
327 on the machine. That person would then have write access to the kernel
328 source.</para>
329
330 <note>
331 <para>In many cases, the configuration of the kernel will need to be
332 updated for packages that will be installed later in BLFS. Unlike
333 other packages, it is not necessary to remove the kernel source tree
334 after the newly built kernel is installed.</para>
335
336 <para>If the kernel source tree is going to be retained, run
337 <command>chown -R 0:0</command> on the <filename
338 class="directory">linux-&linux-version;</filename> directory to ensure
339 all files are owned by user <emphasis>root</emphasis>.</para>
340 </note>
341
342 <warning>
343 <para>Some kernel documentation recommends creating a symlink from
344 <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
345 source directory. This is specific to kernels prior to the 2.6 series and
346 <emphasis>must not</emphasis> be created on an LFS system as it can cause
347 problems for packages you may wish to build once your base LFS system is
348 complete.</para>
349 </warning>
350
351 <warning>
352 <para>The headers in the system's <filename
353 class="directory">include</filename> directory (<filename
354 class="directory">/usr/include</filename>) should
355 <emphasis>always</emphasis> be the ones against which Glibc was compiled,
356 that is, the sanitised headers installed in <xref
357 linkend="ch-tools-linux-headers"/>. Therefore, they should
358 <emphasis>never</emphasis> be replaced by either the raw kernel headers
359 or any other kernel sanitized headers.</para>
360 </warning>
361
362 </sect2>
363
364 <sect2 id="conf-modprobe" role="configuration">
365 <title>Configuring Linux Module Load Order</title>
366
367 <indexterm zone="conf-modprobe">
368 <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
369 </indexterm>
370
371 <para>Most of the time Linux modules are loaded automatically, but
372 sometimes it needs some specific direction. The program that loads
373 modules, <command>modprobe</command> or <command>insmod</command>, uses
374 <filename>/etc/modprobe.d/usb.conf</filename> for this purpose. This file
375 needs to be created so that if the USB drivers (ehci_hcd, ohci_hcd and
376 uhci_hcd) have been built as modules, they will be loaded in the correct
377 order; ehci_hcd needs to be loaded prior to ohci_hcd and uhci_hcd in order
378 to avoid a warning being output at boot time.</para>
379
380 <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
381 the following:</para>
382
383<screen><userinput>install -v -m755 -d /etc/modprobe.d
384cat &gt; /etc/modprobe.d/usb.conf &lt;&lt; "EOF"
385<literal># Begin /etc/modprobe.d/usb.conf
386
387install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
388install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
389
390# End /etc/modprobe.d/usb.conf</literal>
391EOF</userinput></screen>
392
393 </sect2>
394
395 <sect2 id="contents-kernel" role="content">
396 <title>Contents of Linux</title>
397
398 <segmentedlist>
399 <segtitle>Installed files</segtitle>
400 <segtitle>Installed directories</segtitle>
401
402 <seglistitem>
403 <seg>config-&linux-version;,
404 vmlinuz-&linux-version;-lfs-&version;,
405 and System.map-&linux-version;</seg>
406 <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
407 </seglistitem>
408 </segmentedlist>
409
410 <variablelist>
411 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
412 <?dbfo list-presentation="list"?>
413 <?dbhtml list-presentation="table"?>
414
415 <varlistentry id="config">
416 <term><filename>config-&linux-version;</filename></term>
417 <listitem>
418 <para>Contains all the configuration selections for the kernel</para>
419 <indexterm zone="ch-bootable-kernel config">
420 <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
421 </indexterm>
422 </listitem>
423 </varlistentry>
424
425 <varlistentry id="lfskernel">
426 <term><filename>vmlinuz-&linux-version;-lfs-&version;</filename></term>
427 <listitem>
428 <para>The engine of the Linux system. When turning on the computer,
429 the kernel is the first part of the operating system that gets loaded.
430 It detects and initializes all components of the computer's hardware,
431 then makes these components available as a tree of files to the
432 software and turns a single CPU into a multitasking machine capable
433 of running scores of programs seemingly at the same time</para>
434 <indexterm zone="ch-bootable-kernel lfskernel">
435 <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
436 </indexterm>
437 </listitem>
438 </varlistentry>
439
440 <varlistentry id="System.map">
441 <term><filename>System.map-&linux-version;</filename></term>
442 <listitem>
443 <para>A list of addresses and symbols; it maps the entry points and
444 addresses of all the functions and data structures in the
445 kernel</para>
446 <indexterm zone="ch-bootable-kernel System.map">
447 <primary sortas="e-/boot/System.map">/boot/System.map-&linux-version;</primary>
448 </indexterm>
449 </listitem>
450 </varlistentry>
451
452 </variablelist>
453
454 </sect2>
455
456</sect1>
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