source: chapter08/kernel.xml@ 7f599a3

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Last change on this file since 7f599a3 was 7f599a3, checked in by Bruce Dubbs <bdubbs@…>, 6 years ago

Remove obsolete code

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@11179 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 "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>linux</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-ch8-sbu;</seg>
34 <seg>&linux-ch8-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 <!-- Support for compiling a keymap into the kernel is deliberately removed -->
58
59 <para>Configure the kernel via a menu-driven interface. For general
60 information on kernel configuration see <ulink
61 url="&hints-root;kernel-configuration.txt"/>. BLFS has some information
62 regarding particular kernel configuration requirements of packages outside
63 of LFS at <ulink
64 url="&blfs-book;longindex.html#kernel-config-index"/>. Additional
65 information about configuring and building the kernel can be found at
66 <ulink url="http://www.kroah.com/lkn/"/> </para>
67
68 <note>
69
70 <para>A good starting place for setting up the kernel configuration is to
71 run <command>make defconfig</command>. This will set the base
72 configuration to a good state that takes your current system architecture
73 into account.</para>
74
75 <para>Be sure to enable or disable following features or the system might
76 not work correctly or boot at all:</para>
77
78 <screen role="nodump" revision="sysv">
79Device Drivers ---&gt;
80 Generic Driver Options ---&gt;
81 [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
82 [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]</screen>
83
84 <screen role="nodump" revision="systemd">
85General setup -->
86 [ ] Enable deprecated sysfs features to support old userspace tools [CONFIG_SYSFS_DEPRECATED]
87 [ ] Enable deprecated sysfs features by default [CONFIG_SYSFS_DEPRECATED_V2]
88 [*] open by fhandle syscalls [CONFIG_FHANDLE]
89 [ ] Auditing support [CONFIG_AUDIT]
90 [*] Control Group support [CONFIG_CGROUPS]
91Processor type and features ---&gt;
92 [*] Enable seccomp to safely compute untrusted bytecode [CONFIG_SECCOMP]
93Networking support ---&gt;
94 Networking options ---&gt;
95 &lt;*&gt; The IPv6 protocol [CONFIG_IPV6]
96Device Drivers ---&gt;
97 Generic Driver Options ---&gt;
98 [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
99 [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]
100 [ ] Fallback user-helper invocation for firmware loading [CONFIG_FW_LOADER_USER_HELPER]
101Firmware Drivers ---&gt;
102 [*] Export DMI identification via sysfs to userspace [CONFIG_DMIID]
103File systems ---&gt;
104 [*] Inotify support for userspace [CONFIG_INOTIFY_USER]
105 &lt;*&gt; Kernel automounter version 4 support (also supports v3) [CONFIG_AUTOFS4_FS]
106 Pseudo filesystems ---&gt;
107 [*] Tmpfs POSIX Access Control Lists [CONFIG_TMPFS_POSIX_ACL]
108 [*] Tmpfs extended attributes [CONFIG_TMPFS_XATTR]</screen>
109
110 </note>
111
112 <note revision="systemd">
113 <para>While "The IPv6 Protocol" is not strictly
114 required, it is highly recommended by the systemd developers.</para>
115 </note>
116
117 <para revision="sysv">There are several other options that may be desired
118 depending on the requirements for the system. For a list of options needed
119 for BLFS packages, see the <ulink
120 url="&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index">BLFS
121 Index of Kernel Settings</ulink>
122 (&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index).</para>
123
124 <note>
125 <para>If your host hardware is using UEFI, then the 'make defconfig'
126 above should automatically add in some EFI-related kernel options.</para>
127
128 <para>In order to allow your LFS kernel to be booted from within your
129 host's UEFI boot environment, your kernel must have this option
130 selected:</para>
131
132<screen role="nodump">Processor type and features ---&gt;
133 [*] EFI stub support [CONFIG_EFI_STUB]</screen>
134
135 <para>A fuller description of managing UEFI environments from within LFS
136 is covered by the lfs-uefi.txt hint at
137 <ulink
138 url="http://www.linuxfromscratch.org/hints/downloads/files/lfs-uefi.txt"/>.
139 </para>
140 </note>
141
142 <variablelist>
143 <title>The rationale for the above configuration items:</title>
144
145 <varlistentry>
146 <term><parameter>Support for uevent helper</parameter></term>
147 <listitem>
148 <para>Having this option set may interfere with device
149 management when using Udev/Eudev. </para>
150 </listitem>
151 </varlistentry>
152
153 <varlistentry>
154 <term><parameter>Maintain a devtmpfs</parameter></term>
155 <listitem>
156 <para>This will create automated device nodes which are populated by the
157 kernel, even without Udev running. Udev then runs on top of this,
158 managing permissions and adding symlinks. This configuration
159 item is required for all users of Udev/Eudev.</para>
160 </listitem>
161 </varlistentry>
162
163 </variablelist>
164
165<screen role="nodump"><userinput>make menuconfig</userinput></screen>
166
167 <variablelist>
168 <title>The meaning of optional make environment variables:</title>
169
170 <varlistentry>
171 <term><parameter>LANG=&lt;host_LANG_value&gt; LC_ALL=</parameter></term>
172 <listitem>
173 <para>This establishes the locale setting to the one used on the
174 host. This may be needed for a proper menuconfig ncurses interface
175 line drawing on a UTF-8 linux text console.</para>
176
177 <para>If used, be sure to replace
178 <replaceable>&lt;host_LANG_value&gt;</replaceable> by the value of
179 the <envar>$LANG</envar> variable from your host. You can
180 alternatively use instead the host's value of <envar>$LC_ALL</envar>
181 or <envar>$LC_CTYPE</envar>.</para>
182 </listitem>
183 </varlistentry>
184
185 </variablelist>
186
187 <para>Alternatively, <command>make oldconfig</command> may be more
188 appropriate in some situations. See the <filename>README</filename>
189 file for more information.</para>
190
191 <para>If desired, skip kernel configuration by copying the kernel
192 config file, <filename>.config</filename>, from the host system
193 (assuming it is available) to the unpacked <filename
194 class="directory">linux-&linux-version;</filename> directory. However,
195 we do not recommend this option. It is often better to explore all the
196 configuration menus and create the kernel configuration from
197 scratch.</para>
198
199 <para>Compile the kernel image and modules:</para>
200
201<screen><userinput remap="make">make</userinput></screen>
202
203 <para>If using kernel modules, module configuration in <filename
204 class="directory">/etc/modprobe.d</filename> may be required.
205 Information pertaining to modules and kernel configuration is
206 located in <xref linkend="ch-scripts-udev"/> and in the kernel
207 documentation in the <filename
208 class="directory">linux-&linux-version;/Documentation</filename> directory.
209 Also, <filename>modprobe.d(5)</filename> may be of interest.</para>
210
211 <para>Install the modules, if the kernel configuration uses them:</para>
212
213<screen><userinput remap="install">make modules_install</userinput></screen>
214
215 <para>After kernel compilation is complete, additional steps are
216 required to complete the installation. Some files need to be copied to
217 the <filename class="directory">/boot</filename> directory.</para>
218
219 <caution>
220 <para>If the host system has a separate /boot partition, the
221 files copied below should go there. The easiest way to do that
222 is to bind /boot on the host to /mnt/lfs/boot before proceeding.
223 As the root user in the <emphasis>host system</emphasis>:</para>
224
225<screen role="nodump"><userinput>mount --bind /boot /mnt/lfs/boot</userinput></screen>
226 </caution>
227
228 <para>The path to the kernel image may vary depending on the platform being
229 used. The filename below can be changed to suit your taste, but the stem of
230 the filename should be <emphasis>vmlinuz</emphasis> to be compatible with
231 the automatic setup of the boot process described in the next section. The
232 following command assumes an x86 architecture:</para>
233
234<screen revision="sysv"><userinput remap="install">cp -v arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
235
236<screen revision="systemd"><userinput remap="install">cp -v arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&versiond;</userinput></screen>
237
238 <para><filename>System.map</filename> is a symbol file for the kernel.
239 It maps the function entry points of every function in the kernel API,
240 as well as the addresses of the kernel data structures for the running
241 kernel. It is used as a resource when investigating kernel problems.
242 Issue the following command to install the map file:</para>
243
244<screen><userinput remap="install">cp -v System.map /boot/System.map-&linux-version;</userinput></screen>
245
246 <para>The kernel configuration file <filename>.config</filename>
247 produced by the <command>make menuconfig</command> step
248 above contains all the configuration selections for the kernel
249 that was just compiled. It is a good idea to keep this file for future
250 reference:</para>
251
252<screen><userinput remap="install">cp -v .config /boot/config-&linux-version;</userinput></screen>
253
254 <para>Install the documentation for the Linux kernel:</para>
255
256<screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
257cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
258
259 <para>It is important to note that the files in the kernel source
260 directory are not owned by <emphasis>root</emphasis>. Whenever a
261 package is unpacked as user <emphasis>root</emphasis> (like we did
262 inside chroot), the files have the user and group IDs of whatever
263 they were on the packager's computer. This is usually not a problem
264 for any other package to be installed because the source tree is
265 removed after the installation. However, the Linux source tree is
266 often retained for a long time. Because of this, there is a chance
267 that whatever user ID the packager used will be assigned to somebody
268 on the machine. That person would then have write access to the kernel
269 source.</para>
270
271 <note>
272 <para>In many cases, the configuration of the kernel will need to be
273 updated for packages that will be installed later in BLFS. Unlike
274 other packages, it is not necessary to remove the kernel source tree
275 after the newly built kernel is installed.</para>
276
277 <para>If the kernel source tree is going to be retained, run
278 <command>chown -R 0:0</command> on the <filename
279 class="directory">linux-&linux-version;</filename> directory to ensure
280 all files are owned by user <emphasis>root</emphasis>.</para>
281 </note>
282
283 <warning>
284 <para>Some kernel documentation recommends creating a symlink from
285 <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
286 source directory. This is specific to kernels prior to the 2.6 series and
287 <emphasis>must not</emphasis> be created on an LFS system as it can cause
288 problems for packages you may wish to build once your base LFS system is
289 complete.</para>
290 </warning>
291
292 <warning>
293 <para>The headers in the system's <filename
294 class="directory">include</filename> directory (<filename
295 class="directory">/usr/include</filename>) should
296 <emphasis>always</emphasis> be the ones against which Glibc was compiled,
297 that is, the sanitised headers installed in <xref
298 linkend="ch-system-linux-headers"/>. Therefore, they should
299 <emphasis>never</emphasis> be replaced by either the raw kernel headers
300 or any other kernel sanitized headers.</para>
301 </warning>
302
303 </sect2>
304
305 <sect2 id="conf-modprobe" role="configuration">
306 <title>Configuring Linux Module Load Order</title>
307
308 <indexterm zone="conf-modprobe">
309 <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
310 </indexterm>
311
312 <para>Most of the time Linux modules are loaded automatically, but
313 sometimes it needs some specific direction. The program that loads
314 modules, <command>modprobe</command> or <command>insmod</command>, uses
315 <filename>/etc/modprobe.d/usb.conf</filename> for this purpose. This file
316 needs to be created so that if the USB drivers (ehci_hcd, ohci_hcd and
317 uhci_hcd) have been built as modules, they will be loaded in the correct
318 order; ehci_hcd needs to be loaded prior to ohci_hcd and uhci_hcd in order
319 to avoid a warning being output at boot time.</para>
320
321 <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
322 the following:</para>
323
324<screen><userinput>install -v -m755 -d /etc/modprobe.d
325cat &gt; /etc/modprobe.d/usb.conf &lt;&lt; "EOF"
326<literal># Begin /etc/modprobe.d/usb.conf
327
328install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
329install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
330
331# End /etc/modprobe.d/usb.conf</literal>
332EOF</userinput></screen>
333
334 </sect2>
335
336 <sect2 id="contents-kernel" role="content">
337 <title>Contents of Linux</title>
338
339 <segmentedlist>
340 <segtitle>Installed files</segtitle>
341 <segtitle>Installed directories</segtitle>
342
343 <seglistitem>
344 <seg>config-&linux-version;,
345 <phrase revision="sysv">vmlinuz-&linux-version;-lfs-&version;,</phrase>
346 <phrase revision="systemd">vmlinuz-&linux-version;-lfs-&versiond;,</phrase>
347 and System.map-&linux-version;</seg>
348 <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
349 </seglistitem>
350 </segmentedlist>
351
352 <variablelist>
353 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
354 <?dbfo list-presentation="list"?>
355 <?dbhtml list-presentation="table"?>
356
357 <varlistentry id="config">
358 <term><filename>config-&linux-version;</filename></term>
359 <listitem>
360 <para>Contains all the configuration selections for the kernel</para>
361 <indexterm zone="ch-bootable-kernel config">
362 <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
363 </indexterm>
364 </listitem>
365 </varlistentry>
366
367 <varlistentry id="lfskernel">
368 <term revision="sysv"><filename>vmlinuz-&linux-version;-lfs-&version;</filename></term>
369 <term revision="systemd"><filename>vmlinuz-&linux-version;-lfs-&versiond;</filename></term>
370 <listitem>
371 <para>The engine of the Linux system. When turning on the computer,
372 the kernel is the first part of the operating system that gets loaded.
373 It detects and initializes all components of the computer's hardware,
374 then makes these components available as a tree of files to the
375 software and turns a single CPU into a multitasking machine capable
376 of running scores of programs seemingly at the same time</para>
377 <indexterm zone="ch-bootable-kernel lfskernel">
378 <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
379 </indexterm>
380 </listitem>
381 </varlistentry>
382
383 <varlistentry id="System.map">
384 <term><filename>System.map-&linux-version;</filename></term>
385 <listitem>
386 <para>A list of addresses and symbols; it maps the entry points and
387 addresses of all the functions and data structures in the
388 kernel</para>
389 <indexterm zone="ch-bootable-kernel System.map">
390 <primary sortas="e-/boot/System.map">/boot/System.map-&linux-version;</primary>
391 </indexterm>
392 </listitem>
393 </varlistentry>
394
395 </variablelist>
396
397 </sect2>
398
399</sect1>
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