source: chapter10/kernel.xml@ 7bfb571

Last change on this file since 7bfb571 was 7bfb571, checked in by William Harrington <kb0iic@…>, 2 years ago

Kernel (systemd): Add CONFIG_MEMCG as required (systemd-oomd).

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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>
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>
105 <para>Be sure to enable/disable/set the following features or the system might
106 not work correctly or boot at all:</para>
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]</screen>
118 <screen role="nodump" revision="systemd">General setup -->
119 [ ] Auditing Support [CONFIG_AUDIT]
120 &lt; &gt; Enable kernel headers through /sys/kernel/kheaders.tar.xz [CONFIG_IKHEADERS]
121 [*] Control Group support [CONFIG_CGROUPS] ---&gt;
122 [*] Memory controller [CONFIG_MEMCG]
123 [ ] Enable deprecated sysfs features to support old userspace tools [CONFIG_SYSFS_DEPRECATED]
124 [*] Configure standard kernel features (expert users) [CONFIG_EXPERT] ---&gt;
125 [*] open by fhandle syscalls [CONFIG_FHANDLE]
126 CPU/Task time and stats accounting ---&gt;
127 [*] Pressure stall information tracking [CONFIG_PSI]
128General architecture-dependent options ---&gt;
129 [*] Enable seccomp to safely compute untrusted bytecode [CONFIG_SECCOMP]
130Networking support ---&gt;
131 Networking options ---&gt;
132 &lt;*&gt; The IPv6 protocol [CONFIG_IPV6]
133Device Drivers ---&gt;
134 Firmware Drivers ---&gt;
135 [*] Export DMI identification via sysfs to userspace [CONFIG_DMIID]
136 Graphics support ---&gt;
137 Frame buffer Devices ---&gt;
138 [*] Support for frame buffer devices ----
139 Generic Driver Options ---&gt;
140 [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
141 [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]
142 Firmware Loader ---&gt;
143 [ ] Enable the firmware sysfs fallback mechanism [CONFIG_FW_LOADER_USER_HELPER]
144File systems ---&gt;
145 [*] Inotify support for userspace [CONFIG_INOTIFY_USER]
146 Pseudo filesystems ---&gt;
147 [*] Tmpfs POSIX Access Control Lists [CONFIG_TMPFS_POSIX_ACL]</screen>
148 </note>
150 <note revision="systemd">
151 <para>While "The IPv6 Protocol" is not strictly
152 required, it is highly recommended by the systemd developers.</para>
153 </note>
155 <para revision="sysv">There are several other options that may be desired
156 depending on the requirements for the system. For a list of options needed
157 for BLFS packages, see the <ulink
158 url="&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index">BLFS
159 Index of Kernel Settings</ulink>
160 (&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index).</para>
162 <note>
163 <para>If your host hardware is using UEFI and you wish to boot the
164 LFS system with it, you should adjust some kernel configuration
165 following <ulink url="&blfs-book;postlfs/grub-setup.html#uefi-kernel">
166 the BLFS page</ulink>.</para>
167 </note>
169 <variablelist>
170 <title>The rationale for the above configuration items:</title>
172 <varlistentry>
173 <term>
174 <parameter>
175 Enable kernel headers through /sys/kernel/kheaders.tar.xz
176 </parameter>
177 </term>
178 <listitem>
179 <para>This will require <command>cpio</command> building the kernel.
180 <command>cpio</command> is not installed by LFS.</para>
181 </listitem>
182 </varlistentry>
184 <varlistentry>
185 <term><parameter>Support for uevent helper</parameter></term>
186 <listitem>
187 <para>Having this option set may interfere with device
188 management when using Udev/Eudev. </para>
189 </listitem>
190 </varlistentry>
192 <varlistentry>
193 <term><parameter>Maintain a devtmpfs</parameter></term>
194 <listitem>
195 <para>This will create automated device nodes which are populated by the
196 kernel, even without Udev running. Udev then runs on top of this,
197 managing permissions and adding symlinks. This configuration
198 item is required for all users of Udev/Eudev.</para>
199 </listitem>
200 </varlistentry>
202 </variablelist>
204 <para>Alternatively, <command>make oldconfig</command> may be more
205 appropriate in some situations. See the <filename>README</filename>
206 file for more information.</para>
208 <para>If desired, skip kernel configuration by copying the kernel
209 config file, <filename>.config</filename>, from the host system
210 (assuming it is available) to the unpacked <filename
211 class="directory">linux-&linux-version;</filename> directory. However,
212 we do not recommend this option. It is often better to explore all the
213 configuration menus and create the kernel configuration from
214 scratch.</para>
216 <para>Compile the kernel image and modules:</para>
218<screen><userinput remap="make">make</userinput></screen>
220 <para>If using kernel modules, module configuration in <filename
221 class="directory">/etc/modprobe.d</filename> may be required.
222 Information pertaining to modules and kernel configuration is
223 located in <xref linkend="ch-config-udev"/> and in the kernel
224 documentation in the <filename
225 class="directory">linux-&linux-version;/Documentation</filename> directory.
226 Also, <filename>modprobe.d(5)</filename> may be of interest.</para>
228 <para>Unless module support has been disabled in the kernel configuration,
229 install the modules with:</para>
231<screen><userinput remap="install">make modules_install</userinput></screen>
233 <para>After kernel compilation is complete, additional steps are
234 required to complete the installation. Some files need to be copied to
235 the <filename class="directory">/boot</filename> directory.</para>
237 <caution>
238 <para>If the host system has a separate /boot partition, the files copied
239 below should go there. The easiest way to do that is to bind /boot on the
240 host (outside chroot) to /mnt/lfs/boot before proceeding. As the root
241 user in the <emphasis>host system</emphasis>:</para>
243<screen role="nodump"><userinput>mount --bind /boot /mnt/lfs/boot</userinput></screen>
244 </caution>
246 <para>The path to the kernel image may vary depending on the platform being
247 used. The filename below can be changed to suit your taste, but the stem of
248 the filename should be <emphasis>vmlinuz</emphasis> to be compatible with
249 the automatic setup of the boot process described in the next section. The
250 following command assumes an ARM64 architecture:</para>
252<screen><userinput remap="install">cp -iv arch/arm64/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
254 <para><filename></filename> is a symbol file for the kernel.
255 It maps the function entry points of every function in the kernel API,
256 as well as the addresses of the kernel data structures for the running
257 kernel. It is used as a resource when investigating kernel problems.
258 Issue the following command to install the map file:</para>
260<screen><userinput remap="install">cp -iv /boot/;</userinput></screen>
262 <para>The kernel configuration file <filename>.config</filename>
263 produced by the <command>make menuconfig</command> step
264 above contains all the configuration selections for the kernel
265 that was just compiled. It is a good idea to keep this file for future
266 reference:</para>
268<screen><userinput remap="install">cp -iv .config /boot/config-&linux-version;</userinput></screen>
270 <para>Install the documentation for the Linux kernel:</para>
272<screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
273cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
275 <para>It is important to note that the files in the kernel source
276 directory are not owned by <emphasis>root</emphasis>. Whenever a
277 package is unpacked as user <emphasis>root</emphasis> (like we did
278 inside chroot), the files have the user and group IDs of whatever
279 they were on the packager's computer. This is usually not a problem
280 for any other package to be installed because the source tree is
281 removed after the installation. However, the Linux source tree is
282 often retained for a long time. Because of this, there is a chance
283 that whatever user ID the packager used will be assigned to somebody
284 on the machine. That person would then have write access to the kernel
285 source.</para>
287 <note>
288 <para>In many cases, the configuration of the kernel will need to be
289 updated for packages that will be installed later in BLFS. Unlike
290 other packages, it is not necessary to remove the kernel source tree
291 after the newly built kernel is installed.</para>
293 <para>If the kernel source tree is going to be retained, run
294 <command>chown -R 0:0</command> on the <filename
295 class="directory">linux-&linux-version;</filename> directory to ensure
296 all files are owned by user <emphasis>root</emphasis>.</para>
297 </note>
299 <warning>
300 <para>Some kernel documentation recommends creating a symlink from
301 <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
302 source directory. This is specific to kernels prior to the 2.6 series and
303 <emphasis>must not</emphasis> be created on an LFS system as it can cause
304 problems for packages you may wish to build once your base LFS system is
305 complete.</para>
306 </warning>
308 <warning>
309 <para>The headers in the system's <filename
310 class="directory">include</filename> directory (<filename
311 class="directory">/usr/include</filename>) should
312 <emphasis>always</emphasis> be the ones against which Glibc was compiled,
313 that is, the sanitised headers installed in <xref
314 linkend="ch-tools-linux-headers"/>. Therefore, they should
315 <emphasis>never</emphasis> be replaced by either the raw kernel headers
316 or any other kernel sanitized headers.</para>
317 </warning>
319 </sect2>
321 <sect2 id="conf-modprobe" role="configuration">
322 <title>Configuring Linux Module Load Order</title>
324 <indexterm zone="conf-modprobe">
325 <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
326 </indexterm>
328 <para>Most of the time Linux modules are loaded automatically, but
329 sometimes it needs some specific direction. The program that loads
330 modules, <command>modprobe</command> or <command>insmod</command>, uses
331 <filename>/etc/modprobe.d/usb.conf</filename> for this purpose. This file
332 needs to be created so that if the USB drivers (ehci_hcd, ohci_hcd and
333 uhci_hcd) have been built as modules, they will be loaded in the correct
334 order; ehci_hcd needs to be loaded prior to ohci_hcd and uhci_hcd in order
335 to avoid a warning being output at boot time.</para>
337 <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
338 the following:</para>
340<screen><userinput>install -v -m755 -d /etc/modprobe.d
341cat &gt; /etc/modprobe.d/usb.conf &lt;&lt; "EOF"
342<literal># Begin /etc/modprobe.d/usb.conf
344install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
345install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
347# End /etc/modprobe.d/usb.conf</literal>
350 </sect2>
352 <sect2 id="contents-kernel" role="content">
353 <title>Contents of Linux</title>
355 <segmentedlist>
356 <segtitle>Installed files</segtitle>
357 <segtitle>Installed directories</segtitle>
359 <seglistitem>
360 <seg>config-&linux-version;,
361 vmlinuz-&linux-version;-lfs-&version;,
362 and;</seg>
363 <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
364 </seglistitem>
365 </segmentedlist>
367 <variablelist>
368 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
369 <?dbfo list-presentation="list"?>
370 <?dbhtml list-presentation="table"?>
372 <varlistentry id="config">
373 <term><filename>config-&linux-version;</filename></term>
374 <listitem>
375 <para>Contains all the configuration selections for the kernel</para>
376 <indexterm zone="ch-bootable-kernel config">
377 <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
378 </indexterm>
379 </listitem>
380 </varlistentry>
382 <varlistentry id="lfskernel">
383 <term><filename>vmlinuz-&linux-version;-lfs-&version;</filename></term>
384 <listitem>
385 <para>The engine of the Linux system. When turning on the computer,
386 the kernel is the first part of the operating system that gets loaded.
387 It detects and initializes all components of the computer's hardware,
388 then makes these components available as a tree of files to the
389 software and turns a single CPU into a multitasking machine capable
390 of running scores of programs seemingly at the same time</para>
391 <indexterm zone="ch-bootable-kernel lfskernel">
392 <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
393 </indexterm>
394 </listitem>
395 </varlistentry>
397 <varlistentry id="">
398 <term><filename>;</filename></term>
399 <listitem>
400 <para>A list of addresses and symbols; it maps the entry points and
401 addresses of all the functions and data structures in the
402 kernel</para>
403 <indexterm zone="ch-bootable-kernel">
404 <primary sortas="e-/boot/">/boot/;</primary>
405 </indexterm>
406 </listitem>
407 </varlistentry>
409 </variablelist>
411 </sect2>
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