source: chapter10/kernel.xml@ 029f725

xry111/clfs-ng
Last change on this file since 029f725 was 029f725, checked in by Xi Ruoyao <xry111@…>, 2 years ago

clfs-ng: mount /boot before installing the kernel
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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>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] ---&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>
149
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>
154
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>
161
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>
168
169 <variablelist>
170 <title>The rationale for the above configuration items:</title>
171
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>
183
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>
191
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>
201
202 </variablelist>
203
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>
207
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>
215
216 <para>Compile the kernel image and modules:</para>
217
218<screen><userinput remap="make">make</userinput></screen>
219
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>
227
228 <para>Unless module support has been disabled in the kernel configuration,
229 install the modules with:</para>
230
231<screen><userinput remap="install">make modules_install</userinput></screen>
232
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>
236
237 <caution>
238 <para>As the cross-built LFS system has a separate /boot partition,
239 the files copied below should go there. The easiest way to do that is
240 to mount <filename class="directory">/boot</filename> before
241 proceeding. As the root user:</para>
242
243<screen role="nodump"><userinput>mount /boot</userinput></screen>
244
245 <para>We don't need to specify the path to the device node, as it's
246 already given in <filename>/etc/fstab</filename>.</para>
247 </caution>
248
249 <para>The path to the kernel image may vary depending on the platform being
250 used. The filename below can be changed to suit your taste, but the stem of
251 the filename should be <emphasis>vmlinuz</emphasis> to be compatible with
252 the automatic setup of the boot process described in the next section. The
253 following command assumes an x86 architecture:</para>
254
255<screen><userinput remap="install">cp -iv arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
256
257 <para><filename>System.map</filename> is a symbol file for the kernel.
258 It maps the function entry points of every function in the kernel API,
259 as well as the addresses of the kernel data structures for the running
260 kernel. It is used as a resource when investigating kernel problems.
261 Issue the following command to install the map file:</para>
262
263<screen><userinput remap="install">cp -iv System.map /boot/System.map-&linux-version;</userinput></screen>
264
265 <para>The kernel configuration file <filename>.config</filename>
266 produced by the <command>make menuconfig</command> step
267 above contains all the configuration selections for the kernel
268 that was just compiled. It is a good idea to keep this file for future
269 reference:</para>
270
271<screen><userinput remap="install">cp -iv .config /boot/config-&linux-version;</userinput></screen>
272
273 <para>Install the documentation for the Linux kernel:</para>
274
275<screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
276cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
277
278 <para>It is important to note that the files in the kernel source
279 directory are not owned by <emphasis>root</emphasis>. Whenever a
280 package is unpacked as user <emphasis>root</emphasis> (like we did
281 inside chroot), the files have the user and group IDs of whatever
282 they were on the packager's computer. This is usually not a problem
283 for any other package to be installed because the source tree is
284 removed after the installation. However, the Linux source tree is
285 often retained for a long time. Because of this, there is a chance
286 that whatever user ID the packager used will be assigned to somebody
287 on the machine. That person would then have write access to the kernel
288 source.</para>
289
290 <note>
291 <para>In many cases, the configuration of the kernel will need to be
292 updated for packages that will be installed later in BLFS. Unlike
293 other packages, it is not necessary to remove the kernel source tree
294 after the newly built kernel is installed.</para>
295
296 <para>If the kernel source tree is going to be retained, run
297 <command>chown -R 0:0</command> on the <filename
298 class="directory">linux-&linux-version;</filename> directory to ensure
299 all files are owned by user <emphasis>root</emphasis>.</para>
300 </note>
301
302 <warning>
303 <para>Some kernel documentation recommends creating a symlink from
304 <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
305 source directory. This is specific to kernels prior to the 2.6 series and
306 <emphasis>must not</emphasis> be created on an LFS system as it can cause
307 problems for packages you may wish to build once your base LFS system is
308 complete.</para>
309 </warning>
310
311 <warning>
312 <para>The headers in the system's <filename
313 class="directory">include</filename> directory (<filename
314 class="directory">/usr/include</filename>) should
315 <emphasis>always</emphasis> be the ones against which Glibc was compiled,
316 that is, the sanitised headers installed in <xref
317 linkend="ch-tools-linux-headers"/>. Therefore, they should
318 <emphasis>never</emphasis> be replaced by either the raw kernel headers
319 or any other kernel sanitized headers.</para>
320 </warning>
321
322 </sect2>
323
324 <sect2 id="conf-modprobe" role="configuration">
325 <title>Configuring Linux Module Load Order</title>
326
327 <indexterm zone="conf-modprobe">
328 <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
329 </indexterm>
330
331 <para>Most of the time Linux modules are loaded automatically, but
332 sometimes it needs some specific direction. The program that loads
333 modules, <command>modprobe</command> or <command>insmod</command>, uses
334 <filename>/etc/modprobe.d/usb.conf</filename> for this purpose. This file
335 needs to be created so that if the USB drivers (ehci_hcd, ohci_hcd and
336 uhci_hcd) have been built as modules, they will be loaded in the correct
337 order; ehci_hcd needs to be loaded prior to ohci_hcd and uhci_hcd in order
338 to avoid a warning being output at boot time.</para>
339
340 <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
341 the following:</para>
342
343<screen><userinput>install -v -m755 -d /etc/modprobe.d
344cat &gt; /etc/modprobe.d/usb.conf &lt;&lt; "EOF"
345<literal># Begin /etc/modprobe.d/usb.conf
346
347install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
348install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
349
350# End /etc/modprobe.d/usb.conf</literal>
351EOF</userinput></screen>
352
353 </sect2>
354
355 <sect2 id="contents-kernel" role="content">
356 <title>Contents of Linux</title>
357
358 <segmentedlist>
359 <segtitle>Installed files</segtitle>
360 <segtitle>Installed directories</segtitle>
361
362 <seglistitem>
363 <seg>config-&linux-version;,
364 vmlinuz-&linux-version;-lfs-&version;,
365 and System.map-&linux-version;</seg>
366 <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
367 </seglistitem>
368 </segmentedlist>
369
370 <variablelist>
371 <bridgehead renderas="sect3">Short Descriptions</bridgehead>
372 <?dbfo list-presentation="list"?>
373 <?dbhtml list-presentation="table"?>
374
375 <varlistentry id="config">
376 <term><filename>config-&linux-version;</filename></term>
377 <listitem>
378 <para>Contains all the configuration selections for the kernel</para>
379 <indexterm zone="ch-bootable-kernel config">
380 <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
381 </indexterm>
382 </listitem>
383 </varlistentry>
384
385 <varlistentry id="lfskernel">
386 <term><filename>vmlinuz-&linux-version;-lfs-&version;</filename></term>
387 <listitem>
388 <para>The engine of the Linux system. When turning on the computer,
389 the kernel is the first part of the operating system that gets loaded.
390 It detects and initializes all components of the computer's hardware,
391 then makes these components available as a tree of files to the
392 software and turns a single CPU into a multitasking machine capable
393 of running scores of programs seemingly at the same time</para>
394 <indexterm zone="ch-bootable-kernel lfskernel">
395 <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
396 </indexterm>
397 </listitem>
398 </varlistentry>
399
400 <varlistentry id="System.map">
401 <term><filename>System.map-&linux-version;</filename></term>
402 <listitem>
403 <para>A list of addresses and symbols; it maps the entry points and
404 addresses of all the functions and data structures in the
405 kernel</para>
406 <indexterm zone="ch-bootable-kernel System.map">
407 <primary sortas="e-/boot/System.map">/boot/System.map-&linux-version;</primary>
408 </indexterm>
409 </listitem>
410 </varlistentry>
411
412 </variablelist>
413
414 </sect2>
415
416</sect1>
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