source: chapter10/kernel.xml@ 3b11ba0

arm
Last change on this file since 3b11ba0 was 3b11ba0, checked in by William Harrington <kb0iic@…>, 2 years ago

Do a minor reword in networkd.xml and move Firmware Drivers to the
Device Drivers section in the systemd kernel configuration.
  • Property mode set to 100644
File size: 17.2 KB
Line 
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]</screen>
117
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]
122 [ ] Enable deprecated sysfs features to support old userspace tools [CONFIG_SYSFS_DEPRECATED]
123 [*] Configure standard kernel features (expert users) [CONFIG_EXPERT] ---&gt;
124 [*] open by fhandle syscalls [CONFIG_FHANDLE]
125 CPU/Task time and stats accounting ---&gt;
126 [*] Pressure stall information tracking [CONFIG_PSI]
127General architecture-dependent options ---&gt;
128 [*] Enable seccomp to safely compute untrusted bytecode [CONFIG_SECCOMP]
129Networking support ---&gt;
130 Networking options ---&gt;
131 &lt;*&gt; The IPv6 protocol [CONFIG_IPV6]
132Device Drivers ---&gt;
133 Firmware Drivers ---&gt;
134 [*] Export DMI identification via sysfs to userspace [CONFIG_DMIID]
135 Graphics support ---&gt;
136 Frame buffer Devices ---&gt;
137 [*] Support for frame buffer devices ----
138 Generic Driver Options ---&gt;
139 [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
140 [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]
141 Firmware Loader ---&gt;
142 [ ] Enable the firmware sysfs fallback mechanism [CONFIG_FW_LOADER_USER_HELPER]
143File systems ---&gt;
144 [*] Inotify support for userspace [CONFIG_INOTIFY_USER]
145 Pseudo filesystems ---&gt;
146 [*] Tmpfs POSIX Access Control Lists [CONFIG_TMPFS_POSIX_ACL]</screen>
147 </note>
148
149 <note revision="systemd">
150 <para>While "The IPv6 Protocol" is not strictly
151 required, it is highly recommended by the systemd developers.</para>
152 </note>
153
154 <para revision="sysv">There are several other options that may be desired
155 depending on the requirements for the system. For a list of options needed
156 for BLFS packages, see the <ulink
157 url="&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index">BLFS
158 Index of Kernel Settings</ulink>
159 (&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index).</para>
160
161 <note>
162 <para>If your host hardware is using UEFI and you wish to boot the
163 LFS system with it, you should adjust some kernel configuration
164 following <ulink url="&blfs-book;postlfs/grub-setup.html#uefi-kernel">
165 the BLFS page</ulink>.</para>
166 </note>
167
168 <variablelist>
169 <title>The rationale for the above configuration items:</title>
170
171 <varlistentry>
172 <term>
173 <parameter>
174 Enable kernel headers through /sys/kernel/kheaders.tar.xz
175 </parameter>
176 </term>
177 <listitem>
178 <para>This will require <command>cpio</command> building the kernel.
179 <command>cpio</command> is not installed by LFS.</para>
180 </listitem>
181 </varlistentry>
182
183 <varlistentry>
184 <term><parameter>Support for uevent helper</parameter></term>
185 <listitem>
186 <para>Having this option set may interfere with device
187 management when using Udev/Eudev. </para>
188 </listitem>
189 </varlistentry>
190
191 <varlistentry>
192 <term><parameter>Maintain a devtmpfs</parameter></term>
193 <listitem>
194 <para>This will create automated device nodes which are populated by the
195 kernel, even without Udev running. Udev then runs on top of this,
196 managing permissions and adding symlinks. This configuration
197 item is required for all users of Udev/Eudev.</para>
198 </listitem>
199 </varlistentry>
200
201 </variablelist>
202
203 <para>Alternatively, <command>make oldconfig</command> may be more
204 appropriate in some situations. See the <filename>README</filename>
205 file for more information.</para>
206
207 <para>If desired, skip kernel configuration by copying the kernel
208 config file, <filename>.config</filename>, from the host system
209 (assuming it is available) to the unpacked <filename
210 class="directory">linux-&linux-version;</filename> directory. However,
211 we do not recommend this option. It is often better to explore all the
212 configuration menus and create the kernel configuration from
213 scratch.</para>
214
215 <para>Compile the kernel image and modules:</para>
216
217<screen><userinput remap="make">make</userinput></screen>
218
219 <para>If using kernel modules, module configuration in <filename
220 class="directory">/etc/modprobe.d</filename> may be required.
221 Information pertaining to modules and kernel configuration is
222 located in <xref linkend="ch-config-udev"/> and in the kernel
223 documentation in the <filename
224 class="directory">linux-&linux-version;/Documentation</filename> directory.
225 Also, <filename>modprobe.d(5)</filename> may be of interest.</para>
226
227 <para>Unless module support has been disabled in the kernel configuration,
228 install the modules with:</para>
229
230<screen><userinput remap="install">make modules_install</userinput></screen>
231
232 <para>After kernel compilation is complete, additional steps are
233 required to complete the installation. Some files need to be copied to
234 the <filename class="directory">/boot</filename> directory.</para>
235
236 <caution>
237 <para>If the host system has a separate /boot partition, the files copied
238 below should go there. The easiest way to do that is to bind /boot on the
239 host (outside chroot) to /mnt/lfs/boot before proceeding. As the root
240 user in the <emphasis>host system</emphasis>:</para>
241
242<screen role="nodump"><userinput>mount --bind /boot /mnt/lfs/boot</userinput></screen>
243 </caution>
244
245 <para>The path to the kernel image may vary depending on the platform being
246 used. The filename below can be changed to suit your taste, but the stem of
247 the filename should be <emphasis>vmlinuz</emphasis> to be compatible with
248 the automatic setup of the boot process described in the next section. The
249 following command assumes an ARM64 architecture:</para>
250
251<screen><userinput remap="install">cp -iv arch/arm64/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
252
253 <para><filename>System.map</filename> is a symbol file for the kernel.
254 It maps the function entry points of every function in the kernel API,
255 as well as the addresses of the kernel data structures for the running
256 kernel. It is used as a resource when investigating kernel problems.
257 Issue the following command to install the map file:</para>
258
259<screen><userinput remap="install">cp -iv System.map /boot/System.map-&linux-version;</userinput></screen>
260
261 <para>The kernel configuration file <filename>.config</filename>
262 produced by the <command>make menuconfig</command> step
263 above contains all the configuration selections for the kernel
264 that was just compiled. It is a good idea to keep this file for future
265 reference:</para>
266
267<screen><userinput remap="install">cp -iv .config /boot/config-&linux-version;</userinput></screen>
268
269 <para>Install the documentation for the Linux kernel:</para>
270
271<screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
272cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
273
274 <para>It is important to note that the files in the kernel source
275 directory are not owned by <emphasis>root</emphasis>. Whenever a
276 package is unpacked as user <emphasis>root</emphasis> (like we did
277 inside chroot), the files have the user and group IDs of whatever
278 they were on the packager's computer. This is usually not a problem
279 for any other package to be installed because the source tree is
280 removed after the installation. However, the Linux source tree is
281 often retained for a long time. Because of this, there is a chance
282 that whatever user ID the packager used will be assigned to somebody
283 on the machine. That person would then have write access to the kernel
284 source.</para>
285
286 <note>
287 <para>In many cases, the configuration of the kernel will need to be
288 updated for packages that will be installed later in BLFS. Unlike
289 other packages, it is not necessary to remove the kernel source tree
290 after the newly built kernel is installed.</para>
291
292 <para>If the kernel source tree is going to be retained, run
293 <command>chown -R 0:0</command> on the <filename
294 class="directory">linux-&linux-version;</filename> directory to ensure
295 all files are owned by user <emphasis>root</emphasis>.</para>
296 </note>
297
298 <warning>
299 <para>Some kernel documentation recommends creating a symlink from
300 <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
301 source directory. This is specific to kernels prior to the 2.6 series and
302 <emphasis>must not</emphasis> be created on an LFS system as it can cause
303 problems for packages you may wish to build once your base LFS system is
304 complete.</para>
305 </warning>
306
307 <warning>
308 <para>The headers in the system's <filename
309 class="directory">include</filename> directory (<filename
310 class="directory">/usr/include</filename>) should
311 <emphasis>always</emphasis> be the ones against which Glibc was compiled,
312 that is, the sanitised headers installed in <xref
313 linkend="ch-tools-linux-headers"/>. Therefore, they should
314 <emphasis>never</emphasis> be replaced by either the raw kernel headers
315 or any other kernel sanitized headers.</para>
316 </warning>
317
318 </sect2>
319
320 <sect2 id="conf-modprobe" role="configuration">
321 <title>Configuring Linux Module Load Order</title>
322
323 <indexterm zone="conf-modprobe">
324 <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
325 </indexterm>
326
327 <para>Most of the time Linux modules are loaded automatically, but
328 sometimes it needs some specific direction. The program that loads
329 modules, <command>modprobe</command> or <command>insmod</command>, uses
330 <filename>/etc/modprobe.d/usb.conf</filename> for this purpose. This file
331 needs to be created so that if the USB drivers (ehci_hcd, ohci_hcd and
332 uhci_hcd) have been built as modules, they will be loaded in the correct
333 order; ehci_hcd needs to be loaded prior to ohci_hcd and uhci_hcd in order
334 to avoid a warning being output at boot time.</para>
335
336 <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
337 the following:</para>
338
339<screen><userinput>install -v -m755 -d /etc/modprobe.d
340cat &gt; /etc/modprobe.d/usb.conf &lt;&lt; "EOF"
341<literal># Begin /etc/modprobe.d/usb.conf
342
343install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
344install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
345
346# End /etc/modprobe.d/usb.conf</literal>
347EOF</userinput></screen>
348
349 </sect2>
350
351 <sect2 id="contents-kernel" role="content">
352 <title>Contents of Linux</title>
353
354 <segmentedlist>
355 <segtitle>Installed files</segtitle>
356 <segtitle>Installed directories</segtitle>
357
358 <seglistitem>
359 <seg>config-&linux-version;,
360 vmlinuz-&linux-version;-lfs-&version;,
361 and System.map-&linux-version;</seg>
362 <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
363 </seglistitem>
364 </segmentedlist>
365
366 <variablelist>
367 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
368 <?dbfo list-presentation="list"?>
369 <?dbhtml list-presentation="table"?>
370
371 <varlistentry id="config">
372 <term><filename>config-&linux-version;</filename></term>
373 <listitem>
374 <para>Contains all the configuration selections for the kernel</para>
375 <indexterm zone="ch-bootable-kernel config">
376 <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
377 </indexterm>
378 </listitem>
379 </varlistentry>
380
381 <varlistentry id="lfskernel">
382 <term><filename>vmlinuz-&linux-version;-lfs-&version;</filename></term>
383 <listitem>
384 <para>The engine of the Linux system. When turning on the computer,
385 the kernel is the first part of the operating system that gets loaded.
386 It detects and initializes all components of the computer's hardware,
387 then makes these components available as a tree of files to the
388 software and turns a single CPU into a multitasking machine capable
389 of running scores of programs seemingly at the same time</para>
390 <indexterm zone="ch-bootable-kernel lfskernel">
391 <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
392 </indexterm>
393 </listitem>
394 </varlistentry>
395
396 <varlistentry id="System.map">
397 <term><filename>System.map-&linux-version;</filename></term>
398 <listitem>
399 <para>A list of addresses and symbols; it maps the entry points and
400 addresses of all the functions and data structures in the
401 kernel</para>
402 <indexterm zone="ch-bootable-kernel System.map">
403 <primary sortas="e-/boot/System.map">/boot/System.map-&linux-version;</primary>
404 </indexterm>
405 </listitem>
406 </varlistentry>
407
408 </variablelist>
409
410 </sect2>
411
412</sect1>
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