source: chapter10/kernel.xml@ c74edb3

ml-11.0 multilib
Last change on this file since c74edb3 was c74edb3, checked in by Thomas Trepl (Moody) <thomas@…>, 3 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 "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
101 <para>A good starting place for setting up the kernel configuration is to
102 run <command>make defconfig</command>. This will set the base
103 configuration to a good state that takes your current system architecture
104 into account.</para>
105
106 <para>Be sure to enable/disable/set the following features or the system might
107 not work correctly or boot at all:</para>
108
109 <screen role="nodump" revision="sysv">Device Drivers ---&gt;
110 Generic Driver Options ---&gt;
111 [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
112 [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]</screen>
113
114 <screen role="nodump" revision="systemd">General setup -->
115 [ ] Auditing Support [CONFIG_AUDIT]
116 [*] Control Group support [CONFIG_CGROUPS]
117 [ ] Enable deprecated sysfs features to support old userspace tools [CONFIG_SYSFS_DEPRECATED]
118 [*] Configure standard kernel features (expert users) [CONFIG_EXPERT] ---&gt;
119 [*] open by fhandle syscalls [CONFIG_FHANDLE]
120Processor type and features ---&gt;
121 [*] Enable seccomp to safely compute untrusted bytecode [CONFIG_SECCOMP]
122Firmware Drivers ---&gt;
123 [*] Export DMI identification via sysfs to userspace [CONFIG_DMIID]
124Networking support ---&gt;
125 Networking options ---&gt;
126 &lt;*&gt; The IPv6 protocol [CONFIG_IPV6]
127Device Drivers ---&gt;
128 Generic Driver Options ---&gt;
129 [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
130 [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]
131 Firmware Loader ---&gt;
132 [ ] Enable the firmware sysfs fallback mechanism [CONFIG_FW_LOADER_USER_HELPER]
133File systems ---&gt;
134 [*] Inotify support for userspace [CONFIG_INOTIFY_USER]
135 Pseudo filesystems ---&gt;
136 [*] Tmpfs POSIX Access Control Lists [CONFIG_TMPFS_POSIX_ACL]</screen>
137 </note>
138
139 <note revision="systemd">
140 <para>While "The IPv6 Protocol" is not strictly
141 required, it is highly recommended by the systemd developers.</para>
142 </note>
143
144 <para revision="sysv">There are several other options that may be desired
145 depending on the requirements for the system. For a list of options needed
146 for BLFS packages, see the <ulink
147 url="&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index">BLFS
148 Index of Kernel Settings</ulink>
149 (&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index).</para>
150
151 <note>
152 <para>If your host hardware is using UEFI and you wish to boot the
153 LFS system with it, you should adjust some kernel configuration
154 following <ulink url="&blfs-book;postlfs/grub-setup.html#uefi-kernel">
155 the BLFS page</ulink>.</para>
156 </note>
157
158 <note arch="ml_32,ml_x32,ml_all">
159 <para>
160 The kernel on a multilib system needs to be able to
161 identify and start binaries compiled for different architectures
162 than the default.
163 </para>
164
165 <para arch="ml_32,ml_all">
166 If support for any 32bit ABI was built, make sure that the option
167 "IA32 Emulation" is selected. The option 'IA32 a.out support' is
168 optional.
169 </para>
170
171 <para arch="ml_x32,ml_all">
172 If support for the x32bit ABI was built, make sure that the option
173 "x32 ABI for 64-bit mode" is selected.
174 </para>
175
176<screen arch="ml_32">Binary Emulations ---&gt;
177 [*] IA32 Emulation
178 &lt;M&gt; IA32 a.out support
179</screen>
180<screen arch="ml_x32">Binary Emulations ---&gt;
181 [*] x32 ABI for 64-bit mode
182</screen>
183<screen arch="ml_all">Binary Emulations ---&gt;
184 [*] IA32 Emulation
185 &lt;M&gt; IA32 a.out support
186 [*] x32 ABI for 64-bit mode
187</screen>
188
189 </note>
190
191 <variablelist>
192 <title>The rationale for the above configuration items:</title>
193
194 <varlistentry>
195 <term><parameter>Support for uevent helper</parameter></term>
196 <listitem>
197 <para>Having this option set may interfere with device
198 management when using Udev/Eudev. </para>
199 </listitem>
200 </varlistentry>
201
202 <varlistentry>
203 <term><parameter>Maintain a devtmpfs</parameter></term>
204 <listitem>
205 <para>This will create automated device nodes which are populated by the
206 kernel, even without Udev running. Udev then runs on top of this,
207 managing permissions and adding symlinks. This configuration
208 item is required for all users of Udev/Eudev.</para>
209 </listitem>
210 </varlistentry>
211
212 </variablelist>
213
214 <para>Alternatively, <command>make oldconfig</command> may be more
215 appropriate in some situations. See the <filename>README</filename>
216 file for more information.</para>
217
218 <para>If desired, skip kernel configuration by copying the kernel
219 config file, <filename>.config</filename>, from the host system
220 (assuming it is available) to the unpacked <filename
221 class="directory">linux-&linux-version;</filename> directory. However,
222 we do not recommend this option. It is often better to explore all the
223 configuration menus and create the kernel configuration from
224 scratch.</para>
225
226 <para>Compile the kernel image and modules:</para>
227
228<screen><userinput remap="make">make</userinput></screen>
229
230 <para>If using kernel modules, module configuration in <filename
231 class="directory">/etc/modprobe.d</filename> may be required.
232 Information pertaining to modules and kernel configuration is
233 located in <xref linkend="ch-config-udev"/> and in the kernel
234 documentation in the <filename
235 class="directory">linux-&linux-version;/Documentation</filename> directory.
236 Also, <filename>modprobe.d(5)</filename> may be of interest.</para>
237
238 <para>Unless module support has been disabled in the kernel configuration,
239 install the modules with:</para>
240
241<screen><userinput remap="install">make modules_install</userinput></screen>
242
243 <para>After kernel compilation is complete, additional steps are
244 required to complete the installation. Some files need to be copied to
245 the <filename class="directory">/boot</filename> directory.</para>
246
247 <caution>
248 <para>If the host system has a separate /boot partition, the files copied
249 below should go there. The easiest way to do that is to bind /boot on the
250 host (outside chroot) to /mnt/lfs/boot before proceeding. As the root
251 user in the <emphasis>host system</emphasis>:</para>
252
253<screen role="nodump"><userinput>mount --bind /boot /mnt/lfs/boot</userinput></screen>
254 </caution>
255
256 <para>The path to the kernel image may vary depending on the platform being
257 used. The filename below can be changed to suit your taste, but the stem of
258 the filename should be <emphasis>vmlinuz</emphasis> to be compatible with
259 the automatic setup of the boot process described in the next section. The
260 following command assumes an x86 architecture:</para>
261
262<screen revision="sysv"><userinput remap="install">cp -iv arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
263
264<screen revision="systemd"><userinput remap="install">cp -iv arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&versiond;</userinput></screen>
265
266 <para><filename>System.map</filename> is a symbol file for the kernel.
267 It maps the function entry points of every function in the kernel API,
268 as well as the addresses of the kernel data structures for the running
269 kernel. It is used as a resource when investigating kernel problems.
270 Issue the following command to install the map file:</para>
271
272<screen><userinput remap="install">cp -iv System.map /boot/System.map-&linux-version;</userinput></screen>
273
274 <para>The kernel configuration file <filename>.config</filename>
275 produced by the <command>make menuconfig</command> step
276 above contains all the configuration selections for the kernel
277 that was just compiled. It is a good idea to keep this file for future
278 reference:</para>
279
280<screen><userinput remap="install">cp -iv .config /boot/config-&linux-version;</userinput></screen>
281
282 <para>Install the documentation for the Linux kernel:</para>
283
284<screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
285cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
286
287 <para>It is important to note that the files in the kernel source
288 directory are not owned by <emphasis>root</emphasis>. Whenever a
289 package is unpacked as user <emphasis>root</emphasis> (like we did
290 inside chroot), the files have the user and group IDs of whatever
291 they were on the packager's computer. This is usually not a problem
292 for any other package to be installed because the source tree is
293 removed after the installation. However, the Linux source tree is
294 often retained for a long time. Because of this, there is a chance
295 that whatever user ID the packager used will be assigned to somebody
296 on the machine. That person would then have write access to the kernel
297 source.</para>
298
299 <note>
300 <para>In many cases, the configuration of the kernel will need to be
301 updated for packages that will be installed later in BLFS. Unlike
302 other packages, it is not necessary to remove the kernel source tree
303 after the newly built kernel is installed.</para>
304
305 <para>If the kernel source tree is going to be retained, run
306 <command>chown -R 0:0</command> on the <filename
307 class="directory">linux-&linux-version;</filename> directory to ensure
308 all files are owned by user <emphasis>root</emphasis>.</para>
309 </note>
310
311 <warning>
312 <para>Some kernel documentation recommends creating a symlink from
313 <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
314 source directory. This is specific to kernels prior to the 2.6 series and
315 <emphasis>must not</emphasis> be created on an LFS system as it can cause
316 problems for packages you may wish to build once your base LFS system is
317 complete.</para>
318 </warning>
319
320 <warning>
321 <para>The headers in the system's <filename
322 class="directory">include</filename> directory (<filename
323 class="directory">/usr/include</filename>) should
324 <emphasis>always</emphasis> be the ones against which Glibc was compiled,
325 that is, the sanitised headers installed in <xref
326 linkend="ch-tools-linux-headers"/>. Therefore, they should
327 <emphasis>never</emphasis> be replaced by either the raw kernel headers
328 or any other kernel sanitized headers.</para>
329 </warning>
330
331 </sect2>
332
333 <sect2 id="conf-modprobe" role="configuration">
334 <title>Configuring Linux Module Load Order</title>
335
336 <indexterm zone="conf-modprobe">
337 <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
338 </indexterm>
339
340 <para>Most of the time Linux modules are loaded automatically, but
341 sometimes it needs some specific direction. The program that loads
342 modules, <command>modprobe</command> or <command>insmod</command>, uses
343 <filename>/etc/modprobe.d/usb.conf</filename> for this purpose. This file
344 needs to be created so that if the USB drivers (ehci_hcd, ohci_hcd and
345 uhci_hcd) have been built as modules, they will be loaded in the correct
346 order; ehci_hcd needs to be loaded prior to ohci_hcd and uhci_hcd in order
347 to avoid a warning being output at boot time.</para>
348
349 <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
350 the following:</para>
351
352<screen><userinput>install -v -m755 -d /etc/modprobe.d
353cat &gt; /etc/modprobe.d/usb.conf &lt;&lt; "EOF"
354<literal># Begin /etc/modprobe.d/usb.conf
355
356install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
357install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
358
359# End /etc/modprobe.d/usb.conf</literal>
360EOF</userinput></screen>
361
362 </sect2>
363
364 <sect2 id="contents-kernel" role="content">
365 <title>Contents of Linux</title>
366
367 <segmentedlist>
368 <segtitle>Installed files</segtitle>
369 <segtitle>Installed directories</segtitle>
370
371 <seglistitem>
372 <seg>config-&linux-version;,
373 <phrase revision="sysv">vmlinuz-&linux-version;-lfs-&version;,</phrase>
374 <phrase revision="systemd">vmlinuz-&linux-version;-lfs-&versiond;,</phrase>
375 and System.map-&linux-version;</seg>
376 <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
377 </seglistitem>
378 </segmentedlist>
379
380 <variablelist>
381 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
382 <?dbfo list-presentation="list"?>
383 <?dbhtml list-presentation="table"?>
384
385 <varlistentry id="config">
386 <term><filename>config-&linux-version;</filename></term>
387 <listitem>
388 <para>Contains all the configuration selections for the kernel</para>
389 <indexterm zone="ch-bootable-kernel config">
390 <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
391 </indexterm>
392 </listitem>
393 </varlistentry>
394
395 <varlistentry id="lfskernel">
396 <term revision="sysv"><filename>vmlinuz-&linux-version;-lfs-&version;</filename></term>
397 <term revision="systemd"><filename>vmlinuz-&linux-version;-lfs-&versiond;</filename></term>
398 <listitem>
399 <para>The engine of the Linux system. When turning on the computer,
400 the kernel is the first part of the operating system that gets loaded.
401 It detects and initializes all components of the computer's hardware,
402 then makes these components available as a tree of files to the
403 software and turns a single CPU into a multitasking machine capable
404 of running scores of programs seemingly at the same time</para>
405 <indexterm zone="ch-bootable-kernel lfskernel">
406 <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
407 </indexterm>
408 </listitem>
409 </varlistentry>
410
411 <varlistentry id="System.map">
412 <term><filename>System.map-&linux-version;</filename></term>
413 <listitem>
414 <para>A list of addresses and symbols; it maps the entry points and
415 addresses of all the functions and data structures in the
416 kernel</para>
417 <indexterm zone="ch-bootable-kernel System.map">
418 <primary sortas="e-/boot/System.map">/boot/System.map-&linux-version;</primary>
419 </indexterm>
420 </listitem>
421 </varlistentry>
422
423 </variablelist>
424
425 </sect2>
426
427</sect1>
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