source: chapter10/kernel.xml@ eab5b72

10.0 10.1 10.1-rc1 11.0 11.0-rc1 11.0-rc2 11.0-rc3 ml-11.0 multilib trunk xry111/git-transition xry111/glibc-2.34 xry111/tester-nohack xry111/usr-move
Last change on this file since eab5b72 was eab5b72, checked in by Pierre Labastie <pieere@…>, 15 months ago

Update kernel figures + explain
how to launch the menu interface before telling what to tick in the

git-svn-id: 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 "" [
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 <variablelist>
172 <title>The rationale for the above configuration items:</title>
174 <varlistentry>
175 <term><parameter>Support for uevent helper</parameter></term>
176 <listitem>
177 <para>Having this option set may interfere with device
178 management when using Udev/Eudev. </para>
179 </listitem>
180 </varlistentry>
182 <varlistentry>
183 <term><parameter>Maintain a devtmpfs</parameter></term>
184 <listitem>
185 <para>This will create automated device nodes which are populated by the
186 kernel, even without Udev running. Udev then runs on top of this,
187 managing permissions and adding symlinks. This configuration
188 item is required for all users of Udev/Eudev.</para>
189 </listitem>
190 </varlistentry>
192 </variablelist>
194 <para>Alternatively, <command>make oldconfig</command> may be more
195 appropriate in some situations. See the <filename>README</filename>
196 file for more information.</para>
198 <para>If desired, skip kernel configuration by copying the kernel
199 config file, <filename>.config</filename>, from the host system
200 (assuming it is available) to the unpacked <filename
201 class="directory">linux-&linux-version;</filename> directory. However,
202 we do not recommend this option. It is often better to explore all the
203 configuration menus and create the kernel configuration from
204 scratch.</para>
206 <para>Compile the kernel image and modules:</para>
208<screen><userinput remap="make">make</userinput></screen>
210 <para>If using kernel modules, module configuration in <filename
211 class="directory">/etc/modprobe.d</filename> may be required.
212 Information pertaining to modules and kernel configuration is
213 located in <xref linkend="ch-config-udev"/> and in the kernel
214 documentation in the <filename
215 class="directory">linux-&linux-version;/Documentation</filename> directory.
216 Also, <filename>modprobe.d(5)</filename> may be of interest.</para>
218 <para>Unless module support has been disabled in the kernel configuration,
219 install the modules with:</para>
221<screen><userinput remap="install">make modules_install</userinput></screen>
223 <para>After kernel compilation is complete, additional steps are
224 required to complete the installation. Some files need to be copied to
225 the <filename class="directory">/boot</filename> directory.</para>
227 <caution>
228 <para>If the host system has a separate /boot partition, the files copied
229 below should go there. The easiest way to do that is to bind /boot on the
230 host (outside chroot) to /mnt/lfs/boot before proceeding. As the root
231 user in the <emphasis>host system</emphasis>:</para>
233<screen role="nodump"><userinput>mount --bind /boot /mnt/lfs/boot</userinput></screen>
234 </caution>
236 <para>The path to the kernel image may vary depending on the platform being
237 used. The filename below can be changed to suit your taste, but the stem of
238 the filename should be <emphasis>vmlinuz</emphasis> to be compatible with
239 the automatic setup of the boot process described in the next section. The
240 following command assumes an x86 architecture:</para>
242<screen revision="sysv"><userinput remap="install">cp -iv arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
244<screen revision="systemd"><userinput remap="install">cp -iv arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&versiond;</userinput></screen>
246 <para><filename></filename> is a symbol file for the kernel.
247 It maps the function entry points of every function in the kernel API,
248 as well as the addresses of the kernel data structures for the running
249 kernel. It is used as a resource when investigating kernel problems.
250 Issue the following command to install the map file:</para>
252<screen><userinput remap="install">cp -iv /boot/;</userinput></screen>
254 <para>The kernel configuration file <filename>.config</filename>
255 produced by the <command>make menuconfig</command> step
256 above contains all the configuration selections for the kernel
257 that was just compiled. It is a good idea to keep this file for future
258 reference:</para>
260<screen><userinput remap="install">cp -iv .config /boot/config-&linux-version;</userinput></screen>
262 <para>Install the documentation for the Linux kernel:</para>
264<screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
265cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
267 <para>It is important to note that the files in the kernel source
268 directory are not owned by <emphasis>root</emphasis>. Whenever a
269 package is unpacked as user <emphasis>root</emphasis> (like we did
270 inside chroot), the files have the user and group IDs of whatever
271 they were on the packager's computer. This is usually not a problem
272 for any other package to be installed because the source tree is
273 removed after the installation. However, the Linux source tree is
274 often retained for a long time. Because of this, there is a chance
275 that whatever user ID the packager used will be assigned to somebody
276 on the machine. That person would then have write access to the kernel
277 source.</para>
279 <note>
280 <para>In many cases, the configuration of the kernel will need to be
281 updated for packages that will be installed later in BLFS. Unlike
282 other packages, it is not necessary to remove the kernel source tree
283 after the newly built kernel is installed.</para>
285 <para>If the kernel source tree is going to be retained, run
286 <command>chown -R 0:0</command> on the <filename
287 class="directory">linux-&linux-version;</filename> directory to ensure
288 all files are owned by user <emphasis>root</emphasis>.</para>
289 </note>
291 <warning>
292 <para>Some kernel documentation recommends creating a symlink from
293 <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
294 source directory. This is specific to kernels prior to the 2.6 series and
295 <emphasis>must not</emphasis> be created on an LFS system as it can cause
296 problems for packages you may wish to build once your base LFS system is
297 complete.</para>
298 </warning>
300 <warning>
301 <para>The headers in the system's <filename
302 class="directory">include</filename> directory (<filename
303 class="directory">/usr/include</filename>) should
304 <emphasis>always</emphasis> be the ones against which Glibc was compiled,
305 that is, the sanitised headers installed in <xref
306 linkend="ch-tools-linux-headers"/>. Therefore, they should
307 <emphasis>never</emphasis> be replaced by either the raw kernel headers
308 or any other kernel sanitized headers.</para>
309 </warning>
311 </sect2>
313 <sect2 id="conf-modprobe" role="configuration">
314 <title>Configuring Linux Module Load Order</title>
316 <indexterm zone="conf-modprobe">
317 <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
318 </indexterm>
320 <para>Most of the time Linux modules are loaded automatically, but
321 sometimes it needs some specific direction. The program that loads
322 modules, <command>modprobe</command> or <command>insmod</command>, uses
323 <filename>/etc/modprobe.d/usb.conf</filename> for this purpose. This file
324 needs to be created so that if the USB drivers (ehci_hcd, ohci_hcd and
325 uhci_hcd) have been built as modules, they will be loaded in the correct
326 order; ehci_hcd needs to be loaded prior to ohci_hcd and uhci_hcd in order
327 to avoid a warning being output at boot time.</para>
329 <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
330 the following:</para>
332<screen><userinput>install -v -m755 -d /etc/modprobe.d
333cat &gt; /etc/modprobe.d/usb.conf &lt;&lt; "EOF"
334<literal># Begin /etc/modprobe.d/usb.conf
336install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
337install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
339# End /etc/modprobe.d/usb.conf</literal>
342 </sect2>
344 <sect2 id="contents-kernel" role="content">
345 <title>Contents of Linux</title>
347 <segmentedlist>
348 <segtitle>Installed files</segtitle>
349 <segtitle>Installed directories</segtitle>
351 <seglistitem>
352 <seg>config-&linux-version;,
353 <phrase revision="sysv">vmlinuz-&linux-version;-lfs-&version;,</phrase>
354 <phrase revision="systemd">vmlinuz-&linux-version;-lfs-&versiond;,</phrase>
355 and;</seg>
356 <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
357 </seglistitem>
358 </segmentedlist>
360 <variablelist>
361 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
362 <?dbfo list-presentation="list"?>
363 <?dbhtml list-presentation="table"?>
365 <varlistentry id="config">
366 <term><filename>config-&linux-version;</filename></term>
367 <listitem>
368 <para>Contains all the configuration selections for the kernel</para>
369 <indexterm zone="ch-bootable-kernel config">
370 <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
371 </indexterm>
372 </listitem>
373 </varlistentry>
375 <varlistentry id="lfskernel">
376 <term revision="sysv"><filename>vmlinuz-&linux-version;-lfs-&version;</filename></term>
377 <term revision="systemd"><filename>vmlinuz-&linux-version;-lfs-&versiond;</filename></term>
378 <listitem>
379 <para>The engine of the Linux system. When turning on the computer,
380 the kernel is the first part of the operating system that gets loaded.
381 It detects and initializes all components of the computer's hardware,
382 then makes these components available as a tree of files to the
383 software and turns a single CPU into a multitasking machine capable
384 of running scores of programs seemingly at the same time</para>
385 <indexterm zone="ch-bootable-kernel lfskernel">
386 <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
387 </indexterm>
388 </listitem>
389 </varlistentry>
391 <varlistentry id="">
392 <term><filename>;</filename></term>
393 <listitem>
394 <para>A list of addresses and symbols; it maps the entry points and
395 addresses of all the functions and data structures in the
396 kernel</para>
397 <indexterm zone="ch-bootable-kernel">
398 <primary sortas="e-/boot/">/boot/;</primary>
399 </indexterm>
400 </listitem>
401 </varlistentry>
403 </variablelist>
405 </sect2>
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