source: chapter10/kernel.xml@ 602a01f

Last change on this file since 602a01f was 602a01f, checked in by Thomas Trepl <thomas@…>, 15 months ago

Merge changes from trunk to multilib

git-svn-id: 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

  • Property mode set to 100644
File size: 18.2 KB
1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3 "" [
4 <!ENTITY % general-entities SYSTEM "../general.ent">
5 %general-entities;
8<sect1 id="ch-bootable-kernel" role="wrap">
9 <?dbhtml filename="kernel.html"?>
11 <sect1info condition="script">
12 <productname>kernel</productname>
13 <productnumber>&linux-version;</productnumber>
14 <address>&linux-url;</address>
15 </sect1info>
17 <title>Linux-&linux-version;</title>
19 <indexterm zone="ch-bootable-kernel">
20 <primary sortas="a-Linux">Linux</primary>
21 </indexterm>
23 <sect2 role="package">
24 <title/>
26 <para>The Linux package contains the Linux kernel.</para>
28 <segmentedlist>
29 <segtitle>&buildtime;</segtitle>
30 <segtitle>&diskspace;</segtitle>
32 <seglistitem>
33 <seg>&linux-knl-sbu;</seg>
34 <seg>&linux-knl-du;</seg>
35 </seglistitem>
36 </segmentedlist>
38 </sect2>
40 <sect2 role="installation">
41 <title>Installation of the kernel</title>
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>
48 <para>Prepare for compilation by running the following command:</para>
50<screen><userinput remap="pre">make mrproper</userinput></screen>
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>
57 <para>There are several ways to configure the kernel options. Usually,
58 This is done through a menu-driven interface, for example:</para>
60<screen role="nodump"><userinput>make menuconfig</userinput></screen>
62 <variablelist>
63 <title>The meaning of optional make environment variables:</title>
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>
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>
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>
89 <!-- Support for compiling a keymap into the kernel is deliberately removed -->
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=""/> </para>
99 <note>
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>
106 <para>Be sure to enable/disable/set the following features or the system might
107 not work correctly or boot at all:</para>
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>
114 <screen role="nodump" revision="systemd">General setup -->
115 [*] Control Group support [CONFIG_CGROUPS]
116 [ ] Enable deprecated sysfs features to support old userspace tools [CONFIG_SYSFS_DEPRECATED]
117 [*] Configure standard kernel features (expert users) [CONFIG_EXPERT] ---&gt;
118 [*] open by fhandle syscalls [CONFIG_FHANDLE]
119 [ ] Auditing support [CONFIG_AUDIT]
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 &lt;*&gt; Kernel automounter support (supports v3, v4, and v5) [CONFIG_AUTOFS_FS]
136 Pseudo filesystems ---&gt;
137 [*] Tmpfs POSIX Access Control Lists [CONFIG_TMPFS_POSIX_ACL]
138 [*] Tmpfs extended attributes [CONFIG_TMPFS_XATTR]</screen>
139 </note>
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>
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>
153 <note>
154 <para>If your host hardware is using UEFI, then the 'make defconfig'
155 above should automatically add in some EFI-related kernel options.</para>
157 <para>In order to allow your LFS kernel to be booted from within your
158 host's UEFI boot environment, your kernel must have this option
159 selected:</para>
161<screen role="nodump">Processor type and features ---&gt;
162 [*] EFI stub support [CONFIG_EFI_STUB]</screen>
164 <para>A fuller description of managing UEFI environments from within LFS
165 is covered by the lfs-uefi.txt hint at
166 <ulink
167 url="&hints-root;lfs-uefi.txt"/>.
168 </para>
169 </note>
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>
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>
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>
189<screen arch="ml_32">Binary Emulations ---&gt;
190 [*] IA32 Emulation
191 &lt;M&gt; IA32 a.out support
193<screen arch="ml_x32">Binary Emulations ---&gt;
194 [*] x32 ABI for 64-bit mode
196<screen arch="ml_all">Binary Emulations ---&gt;
197 [*] IA32 Emulation
198 &lt;M&gt; IA32 a.out support
199 [*] x32 ABI for 64-bit mode
202 </note>
204 <variablelist>
205 <title>The rationale for the above configuration items:</title>
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>
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>
225 </variablelist>
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>
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>
239 <para>Compile the kernel image and modules:</para>
241<screen><userinput remap="make">make</userinput></screen>
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>
251 <para>Unless module support has been disabled in the kernel configuration,
252 install the modules with:</para>
254<screen><userinput remap="install">make modules_install</userinput></screen>
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>
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>
266<screen role="nodump"><userinput>mount --bind /boot /mnt/lfs/boot</userinput></screen>
267 </caution>
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>
275<screen revision="sysv"><userinput remap="install">cp -iv arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
277<screen revision="systemd"><userinput remap="install">cp -iv arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&versiond;</userinput></screen>
279 <para><filename></filename> is a symbol file for the kernel.
280 It maps the function entry points of every function in the kernel API,
281 as well as the addresses of the kernel data structures for the running
282 kernel. It is used as a resource when investigating kernel problems.
283 Issue the following command to install the map file:</para>
285<screen><userinput remap="install">cp -iv /boot/;</userinput></screen>
287 <para>The kernel configuration file <filename>.config</filename>
288 produced by the <command>make menuconfig</command> step
289 above contains all the configuration selections for the kernel
290 that was just compiled. It is a good idea to keep this file for future
291 reference:</para>
293<screen><userinput remap="install">cp -iv .config /boot/config-&linux-version;</userinput></screen>
295 <para>Install the documentation for the Linux kernel:</para>
297<screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
298cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
300 <para>It is important to note that the files in the kernel source
301 directory are not owned by <emphasis>root</emphasis>. Whenever a
302 package is unpacked as user <emphasis>root</emphasis> (like we did
303 inside chroot), the files have the user and group IDs of whatever
304 they were on the packager's computer. This is usually not a problem
305 for any other package to be installed because the source tree is
306 removed after the installation. However, the Linux source tree is
307 often retained for a long time. Because of this, there is a chance
308 that whatever user ID the packager used will be assigned to somebody
309 on the machine. That person would then have write access to the kernel
310 source.</para>
312 <note>
313 <para>In many cases, the configuration of the kernel will need to be
314 updated for packages that will be installed later in BLFS. Unlike
315 other packages, it is not necessary to remove the kernel source tree
316 after the newly built kernel is installed.</para>
318 <para>If the kernel source tree is going to be retained, run
319 <command>chown -R 0:0</command> on the <filename
320 class="directory">linux-&linux-version;</filename> directory to ensure
321 all files are owned by user <emphasis>root</emphasis>.</para>
322 </note>
324 <warning>
325 <para>Some kernel documentation recommends creating a symlink from
326 <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
327 source directory. This is specific to kernels prior to the 2.6 series and
328 <emphasis>must not</emphasis> be created on an LFS system as it can cause
329 problems for packages you may wish to build once your base LFS system is
330 complete.</para>
331 </warning>
333 <warning>
334 <para>The headers in the system's <filename
335 class="directory">include</filename> directory (<filename
336 class="directory">/usr/include</filename>) should
337 <emphasis>always</emphasis> be the ones against which Glibc was compiled,
338 that is, the sanitised headers installed in <xref
339 linkend="ch-tools-linux-headers"/>. Therefore, they should
340 <emphasis>never</emphasis> be replaced by either the raw kernel headers
341 or any other kernel sanitized headers.</para>
342 </warning>
344 </sect2>
346 <sect2 id="conf-modprobe" role="configuration">
347 <title>Configuring Linux Module Load Order</title>
349 <indexterm zone="conf-modprobe">
350 <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
351 </indexterm>
353 <para>Most of the time Linux modules are loaded automatically, but
354 sometimes it needs some specific direction. The program that loads
355 modules, <command>modprobe</command> or <command>insmod</command>, uses
356 <filename>/etc/modprobe.d/usb.conf</filename> for this purpose. This file
357 needs to be created so that if the USB drivers (ehci_hcd, ohci_hcd and
358 uhci_hcd) have been built as modules, they will be loaded in the correct
359 order; ehci_hcd needs to be loaded prior to ohci_hcd and uhci_hcd in order
360 to avoid a warning being output at boot time.</para>
362 <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
363 the following:</para>
365<screen><userinput>install -v -m755 -d /etc/modprobe.d
366cat &gt; /etc/modprobe.d/usb.conf &lt;&lt; "EOF"
367<literal># Begin /etc/modprobe.d/usb.conf
369install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
370install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
372# End /etc/modprobe.d/usb.conf</literal>
375 </sect2>
377 <sect2 id="contents-kernel" role="content">
378 <title>Contents of Linux</title>
380 <segmentedlist>
381 <segtitle>Installed files</segtitle>
382 <segtitle>Installed directories</segtitle>
384 <seglistitem>
385 <seg>config-&linux-version;,
386 <phrase revision="sysv">vmlinuz-&linux-version;-lfs-&version;,</phrase>
387 <phrase revision="systemd">vmlinuz-&linux-version;-lfs-&versiond;,</phrase>
388 and;</seg>
389 <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
390 </seglistitem>
391 </segmentedlist>
393 <variablelist>
394 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
395 <?dbfo list-presentation="list"?>
396 <?dbhtml list-presentation="table"?>
398 <varlistentry id="config">
399 <term><filename>config-&linux-version;</filename></term>
400 <listitem>
401 <para>Contains all the configuration selections for the kernel</para>
402 <indexterm zone="ch-bootable-kernel config">
403 <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
404 </indexterm>
405 </listitem>
406 </varlistentry>
408 <varlistentry id="lfskernel">
409 <term revision="sysv"><filename>vmlinuz-&linux-version;-lfs-&version;</filename></term>
410 <term revision="systemd"><filename>vmlinuz-&linux-version;-lfs-&versiond;</filename></term>
411 <listitem>
412 <para>The engine of the Linux system. When turning on the computer,
413 the kernel is the first part of the operating system that gets loaded.
414 It detects and initializes all components of the computer's hardware,
415 then makes these components available as a tree of files to the
416 software and turns a single CPU into a multitasking machine capable
417 of running scores of programs seemingly at the same time</para>
418 <indexterm zone="ch-bootable-kernel lfskernel">
419 <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
420 </indexterm>
421 </listitem>
422 </varlistentry>
424 <varlistentry id="">
425 <term><filename>;</filename></term>
426 <listitem>
427 <para>A list of addresses and symbols; it maps the entry points and
428 addresses of all the functions and data structures in the
429 kernel</para>
430 <indexterm zone="ch-bootable-kernel">
431 <primary sortas="e-/boot/">/boot/;</primary>
432 </indexterm>
433 </listitem>
434 </varlistentry>
436 </variablelist>
438 </sect2>
Note: See TracBrowser for help on using the repository browser.