kernel.xml 17 KB

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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. <sect1 id="ch-bootable-kernel" role="wrap">
  8. <?dbhtml filename="kernel.html"?>
  9. <sect1info condition="script">
  10. <productname>kernel</productname>
  11. <productnumber>&linux-version;</productnumber>
  12. <address>&linux-url;</address>
  13. </sect1info>
  14. <title>Linux-&linux-version;</title>
  15. <indexterm zone="ch-bootable-kernel">
  16. <primary sortas="a-Linux">Linux</primary>
  17. </indexterm>
  18. <sect2 role="package">
  19. <title/>
  20. <para>The Linux package contains the Linux kernel.</para>
  21. <segmentedlist>
  22. <segtitle>&buildtime;</segtitle>
  23. <segtitle>&diskspace;</segtitle>
  24. <seglistitem>
  25. <seg>&linux-ch8-sbu;</seg>
  26. <seg>&linux-ch8-du;</seg>
  27. </seglistitem>
  28. </segmentedlist>
  29. </sect2>
  30. <sect2 role="installation">
  31. <title>Installation of the kernel</title>
  32. <para>Building the kernel involves a few steps&mdash;configuration,
  33. compilation, and installation. Read the <filename>README</filename> file
  34. in the kernel source tree for alternative methods to the way this book
  35. configures the kernel.</para>
  36. <para>Prepare for compilation by running the following command:</para>
  37. <screen><userinput remap="pre">make mrproper</userinput></screen>
  38. <para>This ensures that the kernel tree is absolutely clean. The
  39. kernel team recommends that this command be issued prior to each
  40. kernel compilation. Do not rely on the source tree being clean after
  41. un-tarring.</para>
  42. <!-- Support for compiling a keymap into the kernel is deliberately removed -->
  43. <para>Configure the kernel via a menu-driven interface. For general
  44. information on kernel configuration see <ulink
  45. url="&hints-root;kernel-configuration.txt"/>. BLFS has some information
  46. regarding particular kernel configuration requirements of packages outside
  47. of LFS at <ulink
  48. url="&blfs-book;longindex.html#kernel-config-index"/>. Additional
  49. information about configuring and building the kernel can be found at
  50. <ulink url="http://www.kroah.com/lkn/"/> </para>
  51. <note>
  52. <para>A good starting place for setting up the kernel configuration is to
  53. run <command>make defconfig</command>. This will set the base
  54. configuration to a good state that takes your current system architecture
  55. into account.</para>
  56. <para>Be sure to enable/disable/set the following features or the system might
  57. not work correctly or boot at all:</para>
  58. <screen role="nodump" revision="sysv">
  59. Device Drivers ---&gt;
  60. Generic Driver Options ---&gt;
  61. [ ] Support for uevent helper [CONFIG_UEVENT_HELPER]
  62. [*] Maintain a devtmpfs filesystem to mount at /dev [CONFIG_DEVTMPFS]
  63. Kernel hacking ---&gt;
  64. Choose kernel unwinder (Frame pointer unwinder) ---&gt; [CONFIG_UNWINDER_FRAME_POINTER]</screen>
  65. <screen role="nodump" revision="systemd">
  66. General setup -->
  67. [*] Control Group support [CONFIG_CGROUPS]
  68. [ ] Enable deprecated sysfs features to support old userspace tools [CONFIG_SYSFS_DEPRECATED]
  69. [*] Configure standard kernel features (expert users) [CONFIG_EXPERT] ---&gt;
  70. [*] open by fhandle syscalls [CONFIG_FHANDLE]
  71. [ ] Auditing support [CONFIG_AUDIT]
  72. Processor type and features ---&gt;
  73. [*] Enable seccomp to safely compute untrusted bytecode [CONFIG_SECCOMP]
  74. Firmware Drivers ---&gt;
  75. [*] Export DMI identification via sysfs to userspace [CONFIG_DMIID]
  76. Networking support ---&gt;
  77. Networking options ---&gt;
  78. &lt;*&gt; The IPv6 protocol [CONFIG_IPV6]
  79. Device 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]
  83. Firmware Loader ---&gt;
  84. [ ] Enable the firmware sysfs fallback mechanism [CONFIG_FW_LOADER_USER_HELPER]
  85. File systems ---&gt;
  86. [*] Inotify support for userspace [CONFIG_INOTIFY_USER]
  87. &lt;*&gt; Kernel automounter support (supports v3, v4, and v5) [CONFIG_AUTOFS_FS]
  88. Pseudo filesystems ---&gt;
  89. [*] Tmpfs POSIX Access Control Lists [CONFIG_TMPFS_POSIX_ACL]
  90. [*] Tmpfs extended attributes [CONFIG_TMPFS_XATTR]</screen>
  91. </note>
  92. <note revision="systemd">
  93. <para>While "The IPv6 Protocol" is not strictly
  94. required, it is highly recommended by the systemd developers.</para>
  95. </note>
  96. <para revision="sysv">There are several other options that may be desired
  97. depending on the requirements for the system. For a list of options needed
  98. for BLFS packages, see the <ulink
  99. url="&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index">BLFS
  100. Index of Kernel Settings</ulink>
  101. (&lfs-root;blfs/view/&short-version;/longindex.html#kernel-config-index).</para>
  102. <note>
  103. <para>If your host hardware is using UEFI, then the 'make defconfig'
  104. above should automatically add in some EFI-related kernel options.</para>
  105. <para>In order to allow your LFS kernel to be booted from within your
  106. host's UEFI boot environment, your kernel must have this option
  107. selected:</para>
  108. <screen role="nodump">Processor type and features ---&gt;
  109. [*] EFI stub support [CONFIG_EFI_STUB]</screen>
  110. <para>A fuller description of managing UEFI environments from within LFS
  111. is covered by the lfs-uefi.txt hint at
  112. <ulink
  113. url="&hints-root;lfs-uefi.txt"/>.
  114. </para>
  115. </note>
  116. <variablelist>
  117. <title>The rationale for the above configuration items:</title>
  118. <varlistentry>
  119. <term><parameter>Support for uevent helper</parameter></term>
  120. <listitem>
  121. <para>Having this option set may interfere with device
  122. management when using Udev/Eudev. </para>
  123. </listitem>
  124. </varlistentry>
  125. <varlistentry>
  126. <term><parameter>Maintain a devtmpfs</parameter></term>
  127. <listitem>
  128. <para>This will create automated device nodes which are populated by the
  129. kernel, even without Udev running. Udev then runs on top of this,
  130. managing permissions and adding symlinks. This configuration
  131. item is required for all users of Udev/Eudev.</para>
  132. </listitem>
  133. </varlistentry>
  134. </variablelist>
  135. <screen role="nodump"><userinput>make menuconfig</userinput></screen>
  136. <variablelist>
  137. <title>The meaning of optional make environment variables:</title>
  138. <varlistentry>
  139. <term><parameter>LANG=&lt;host_LANG_value&gt; LC_ALL=</parameter></term>
  140. <listitem>
  141. <para>This establishes the locale setting to the one used on the
  142. host. This may be needed for a proper menuconfig ncurses interface
  143. line drawing on a UTF-8 linux text console.</para>
  144. <para>If used, be sure to replace
  145. <replaceable>&lt;host_LANG_value&gt;</replaceable> by the value of
  146. the <envar>$LANG</envar> variable from your host. You can
  147. alternatively use instead the host's value of <envar>$LC_ALL</envar>
  148. or <envar>$LC_CTYPE</envar>.</para>
  149. </listitem>
  150. </varlistentry>
  151. </variablelist>
  152. <para>Alternatively, <command>make oldconfig</command> may be more
  153. appropriate in some situations. See the <filename>README</filename>
  154. file for more information.</para>
  155. <para>If desired, skip kernel configuration by copying the kernel
  156. config file, <filename>.config</filename>, from the host system
  157. (assuming it is available) to the unpacked <filename
  158. class="directory">linux-&linux-version;</filename> directory. However,
  159. we do not recommend this option. It is often better to explore all the
  160. configuration menus and create the kernel configuration from
  161. scratch.</para>
  162. <para>Compile the kernel image and modules:</para>
  163. <screen><userinput remap="make">make</userinput></screen>
  164. <para>If using kernel modules, module configuration in <filename
  165. class="directory">/etc/modprobe.d</filename> may be required.
  166. Information pertaining to modules and kernel configuration is
  167. located in <xref linkend="ch-config-udev"/> and in the kernel
  168. documentation in the <filename
  169. class="directory">linux-&linux-version;/Documentation</filename> directory.
  170. Also, <filename>modprobe.d(5)</filename> may be of interest.</para>
  171. <para>Unless module support has been disabled in the kernel configuration,
  172. install the modules with:</para>
  173. <screen><userinput remap="install">make modules_install</userinput></screen>
  174. <para>After kernel compilation is complete, additional steps are
  175. required to complete the installation. Some files need to be copied to
  176. the <filename class="directory">/boot</filename> directory.</para>
  177. <caution>
  178. <para>If the host system has a separate /boot partition, the files copied
  179. below should go there. The easiest way to do that is to bind /boot on the
  180. host (outside chroot) to /mnt/lfs/boot before proceeding. As the root
  181. user in the <emphasis>host system</emphasis>:</para>
  182. <screen role="nodump"><userinput>mount --bind /boot /mnt/lfs/boot</userinput></screen>
  183. </caution>
  184. <para>The path to the kernel image may vary depending on the platform being
  185. used. The filename below can be changed to suit your taste, but the stem of
  186. the filename should be <emphasis>vmlinuz</emphasis> to be compatible with
  187. the automatic setup of the boot process described in the next section. The
  188. following command assumes an x86 architecture:</para>
  189. <screen revision="sysv"><userinput remap="install">cp -iv arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
  190. <screen revision="systemd"><userinput remap="install">cp -iv arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&versiond;</userinput></screen>
  191. <para><filename>System.map</filename> is a symbol file for the kernel.
  192. It maps the function entry points of every function in the kernel API,
  193. as well as the addresses of the kernel data structures for the running
  194. kernel. It is used as a resource when investigating kernel problems.
  195. Issue the following command to install the map file:</para>
  196. <screen><userinput remap="install">cp -iv System.map /boot/System.map-&linux-version;</userinput></screen>
  197. <para>The kernel configuration file <filename>.config</filename>
  198. produced by the <command>make menuconfig</command> step
  199. above contains all the configuration selections for the kernel
  200. that was just compiled. It is a good idea to keep this file for future
  201. reference:</para>
  202. <screen><userinput remap="install">cp -iv .config /boot/config-&linux-version;</userinput></screen>
  203. <para>Install the documentation for the Linux kernel:</para>
  204. <screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
  205. cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
  206. <para>It is important to note that the files in the kernel source
  207. directory are not owned by <emphasis>root</emphasis>. Whenever a
  208. package is unpacked as user <emphasis>root</emphasis> (like we did
  209. inside chroot), the files have the user and group IDs of whatever
  210. they were on the packager's computer. This is usually not a problem
  211. for any other package to be installed because the source tree is
  212. removed after the installation. However, the Linux source tree is
  213. often retained for a long time. Because of this, there is a chance
  214. that whatever user ID the packager used will be assigned to somebody
  215. on the machine. That person would then have write access to the kernel
  216. source.</para>
  217. <note>
  218. <para>In many cases, the configuration of the kernel will need to be
  219. updated for packages that will be installed later in BLFS. Unlike
  220. other packages, it is not necessary to remove the kernel source tree
  221. after the newly built kernel is installed.</para>
  222. <para>If the kernel source tree is going to be retained, run
  223. <command>chown -R 0:0</command> on the <filename
  224. class="directory">linux-&linux-version;</filename> directory to ensure
  225. all files are owned by user <emphasis>root</emphasis>.</para>
  226. </note>
  227. <warning>
  228. <para>Some kernel documentation recommends creating a symlink from
  229. <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
  230. source directory. This is specific to kernels prior to the 2.6 series and
  231. <emphasis>must not</emphasis> be created on an LFS system as it can cause
  232. problems for packages you may wish to build once your base LFS system is
  233. complete.</para>
  234. </warning>
  235. <warning>
  236. <para>The headers in the system's <filename
  237. class="directory">include</filename> directory (<filename
  238. class="directory">/usr/include</filename>) should
  239. <emphasis>always</emphasis> be the ones against which Glibc was compiled,
  240. that is, the sanitised headers installed in <xref
  241. linkend="ch-tools-linux-headers"/>. Therefore, they should
  242. <emphasis>never</emphasis> be replaced by either the raw kernel headers
  243. or any other kernel sanitized headers.</para>
  244. </warning>
  245. </sect2>
  246. <sect2 id="conf-modprobe" role="configuration">
  247. <title>Configuring Linux Module Load Order</title>
  248. <indexterm zone="conf-modprobe">
  249. <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
  250. </indexterm>
  251. <para>Most of the time Linux modules are loaded automatically, but
  252. sometimes it needs some specific direction. The program that loads
  253. modules, <command>modprobe</command> or <command>insmod</command>, uses
  254. <filename>/etc/modprobe.d/usb.conf</filename> for this purpose. This file
  255. needs to be created so that if the USB drivers (ehci_hcd, ohci_hcd and
  256. uhci_hcd) have been built as modules, they will be loaded in the correct
  257. order; ehci_hcd needs to be loaded prior to ohci_hcd and uhci_hcd in order
  258. to avoid a warning being output at boot time.</para>
  259. <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
  260. the following:</para>
  261. <screen><userinput>install -v -m755 -d /etc/modprobe.d
  262. cat &gt; /etc/modprobe.d/usb.conf &lt;&lt; "EOF"
  263. <literal># Begin /etc/modprobe.d/usb.conf
  264. install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
  265. install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
  266. # End /etc/modprobe.d/usb.conf</literal>
  267. EOF</userinput></screen>
  268. </sect2>
  269. <sect2 id="contents-kernel" role="content">
  270. <title>Contents of Linux</title>
  271. <segmentedlist>
  272. <segtitle>Installed files</segtitle>
  273. <segtitle>Installed directories</segtitle>
  274. <seglistitem>
  275. <seg>config-&linux-version;,
  276. <phrase revision="sysv">vmlinuz-&linux-version;-lfs-&version;,</phrase>
  277. <phrase revision="systemd">vmlinuz-&linux-version;-lfs-&versiond;,</phrase>
  278. and System.map-&linux-version;</seg>
  279. <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
  280. </seglistitem>
  281. </segmentedlist>
  282. <variablelist>
  283. <bridgehead renderas="sect3">Short Descriptions</bridgehead>
  284. <?dbfo list-presentation="list"?>
  285. <?dbhtml list-presentation="table"?>
  286. <varlistentry id="config">
  287. <term><filename>config-&linux-version;</filename></term>
  288. <listitem>
  289. <para>Contains all the configuration selections for the kernel</para>
  290. <indexterm zone="ch-bootable-kernel config">
  291. <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
  292. </indexterm>
  293. </listitem>
  294. </varlistentry>
  295. <varlistentry id="lfskernel">
  296. <term revision="sysv"><filename>vmlinuz-&linux-version;-lfs-&version;</filename></term>
  297. <term revision="systemd"><filename>vmlinuz-&linux-version;-lfs-&versiond;</filename></term>
  298. <listitem>
  299. <para>The engine of the Linux system. When turning on the computer,
  300. the kernel is the first part of the operating system that gets loaded.
  301. It detects and initializes all components of the computer's hardware,
  302. then makes these components available as a tree of files to the
  303. software and turns a single CPU into a multitasking machine capable
  304. of running scores of programs seemingly at the same time</para>
  305. <indexterm zone="ch-bootable-kernel lfskernel">
  306. <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
  307. </indexterm>
  308. </listitem>
  309. </varlistentry>
  310. <varlistentry id="System.map">
  311. <term><filename>System.map-&linux-version;</filename></term>
  312. <listitem>
  313. <para>A list of addresses and symbols; it maps the entry points and
  314. addresses of all the functions and data structures in the
  315. kernel</para>
  316. <indexterm zone="ch-bootable-kernel System.map">
  317. <primary sortas="e-/boot/System.map">/boot/System.map-&linux-version;</primary>
  318. </indexterm>
  319. </listitem>
  320. </varlistentry>
  321. </variablelist>
  322. </sect2>
  323. </sect1>