kernel.xml 12 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>linux</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-root;view/svn/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><para>Due to recent changes in <application>udev</application>, be sure to
  52. select:</para>
  53. <screen role="nodump">Device Drivers ---&gt;
  54. Generic Driver Options ---&gt;
  55. Maintain a devtmpfs filesystem to mount at /dev</screen></note>
  56. <screen role="nodump"><userinput>make LANG=<replaceable>&lt;host_LANG_value&gt;</replaceable> LC_ALL= menuconfig</userinput></screen>
  57. <variablelist>
  58. <title>The meaning of the make parameters:</title>
  59. <varlistentry>
  60. <term><parameter>LANG=&lt;host_LANG_value&gt; LC_ALL=</parameter></term>
  61. <listitem>
  62. <para>This establishes the locale setting to the one used on the host.
  63. This is needed for a proper menuconfig ncurses interface line
  64. drawing on UTF-8 linux text console.</para>
  65. <para>Be sure to replace <replaceable>&lt;host_LANG_value&gt;</replaceable>
  66. by the value of the <envar>$LANG</envar> variable from your host.
  67. If not set, you could use instead the host's value of <envar>$LC_ALL</envar>
  68. or <envar>$LC_CTYPE</envar>.</para>
  69. </listitem>
  70. </varlistentry>
  71. </variablelist>
  72. <para>Alternatively, <command>make oldconfig</command> may be more
  73. appropriate in some situations. See the <filename>README</filename>
  74. file for more information.</para>
  75. <para>If desired, skip kernel configuration by copying the kernel
  76. config file, <filename>.config</filename>, from the host system
  77. (assuming it is available) to the unpacked <filename
  78. class="directory">linux-&linux-version;</filename> directory. However,
  79. we do not recommend this option. It is often better to explore all the
  80. configuration menus and create the kernel configuration from
  81. scratch.</para>
  82. <para>Compile the kernel image and modules:</para>
  83. <screen><userinput remap="make">make</userinput></screen>
  84. <para>If using kernel modules, module configuration in <filename
  85. class="directory">/etc/modprobe.d</filename> may be required.
  86. Information pertaining to modules and kernel configuration is
  87. located in <xref linkend="ch-scripts-udev"/> and in the kernel
  88. documentation in the <filename
  89. class="directory">linux-&linux-version;/Documentation</filename> directory.
  90. Also, <filename>modprobe.conf(5)</filename> may be of interest.</para>
  91. <para>Install the modules, if the kernel configuration uses them:</para>
  92. <screen><userinput remap="install">make modules_install</userinput></screen>
  93. <para>After kernel compilation is complete, additional steps are
  94. required to complete the installation. Some files need to be copied to
  95. the <filename class="directory">/boot</filename> directory.</para>
  96. <para>The path to the kernel image may vary depending on the platform being
  97. used. The filename below can be changed to suit your taste, but the stem of
  98. the filename should be <emphasis>vmlinuz</emphasis> to be compatible with
  99. the automatic setup of the boot process described in the next section. The
  100. following command assumes an x86 architecture:</para>
  101. <screen><userinput remap="install">cp -v arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
  102. <para><filename>System.map</filename> is a symbol file for the kernel.
  103. It maps the function entry points of every function in the kernel API,
  104. as well as the addresses of the kernel data structures for the running
  105. kernel. It is used as a resource when investigating kernel problems.
  106. Issue the following command to install the map file:</para>
  107. <screen><userinput remap="install">cp -v System.map /boot/System.map-&linux-version;</userinput></screen>
  108. <para>The kernel configuration file <filename>.config</filename>
  109. produced by the <command>make menuconfig</command> step
  110. above contains all the configuration selections for the kernel
  111. that was just compiled. It is a good idea to keep this file for future
  112. reference:</para>
  113. <screen><userinput remap="install">cp -v .config /boot/config-&linux-version;</userinput></screen>
  114. <para>Install the documentation for the Linux kernel:</para>
  115. <screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
  116. cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
  117. <para>It is important to note that the files in the kernel source
  118. directory are not owned by <emphasis>root</emphasis>. Whenever a
  119. package is unpacked as user <emphasis>root</emphasis> (like we did
  120. inside chroot), the files have the user and group IDs of whatever
  121. they were on the packager's computer. This is usually not a problem
  122. for any other package to be installed because the source tree is
  123. removed after the installation. However, the Linux source tree is
  124. often retained for a long time. Because of this, there is a chance
  125. that whatever user ID the packager used will be assigned to somebody
  126. on the machine. That person would then have write access to the kernel
  127. source.</para>
  128. <para>If the kernel source tree is going to be retained, run
  129. <command>chown -R 0:0</command> on the <filename
  130. class="directory">linux-&linux-version;</filename> directory to ensure
  131. all files are owned by user <emphasis>root</emphasis>.</para>
  132. <warning>
  133. <para>Some kernel documentation recommends creating a symlink from
  134. <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
  135. source directory. This is specific to kernels prior to the 2.6 series and
  136. <emphasis>must not</emphasis> be created on an LFS system as it can cause
  137. problems for packages you may wish to build once your base LFS system is
  138. complete.</para>
  139. </warning>
  140. <warning>
  141. <para>The headers in the system's
  142. <filename class="directory">include</filename> directory should
  143. <emphasis>always</emphasis> be the ones against which Glibc was compiled,
  144. that is, the sanitised headers from this Linux kernel tarball.
  145. Therefore, they should <emphasis>never</emphasis> be replaced by either
  146. the raw kernel headers or any other kernel sanitized headers.</para>
  147. </warning>
  148. </sect2>
  149. <sect2 id="conf-modprobe" role="configuration">
  150. <title>Configuring Linux Module Load Order</title>
  151. <indexterm zone="conf-modprobe">
  152. <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
  153. </indexterm>
  154. <para>Most of the time Linux modules are loaded automatically, but
  155. sometimes it needs some specific direction. The program that loads
  156. modules, <command>modprobe</command> or <command>insmod</command>, uses
  157. <filename>/etc/modprobe.d/usb.conf</filename> for this purpose. This file
  158. needs to be created so that if the USB drivers (ehci_hcd, ohci_hcd and
  159. uhci_hcd) have been built as modules, they will be loaded in the correct
  160. order; ehci_hcd needs to be loaded prior to ohci_hcd and uhci_hcd in order
  161. to avoid a warning being output at boot time.</para>
  162. <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
  163. the following:</para>
  164. <screen><userinput>install -v -m755 -d /etc/modprobe.d
  165. cat &gt; /etc/modprobe.d/usb.conf &lt;&lt; "EOF"
  166. <literal># Begin /etc/modprobe.d/usb.conf
  167. install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
  168. install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
  169. # End /etc/modprobe.d/usb.conf</literal>
  170. EOF</userinput></screen>
  171. </sect2>
  172. <sect2 id="contents-kernel" role="content">
  173. <title>Contents of Linux</title>
  174. <segmentedlist>
  175. <segtitle>Installed files</segtitle>
  176. <segtitle>Installed directories</segtitle>
  177. <seglistitem>
  178. <seg>config-&linux-version;,
  179. vmlinux-&linux-version;-lfs-&version;-&linux-version;, and
  180. System.map-&linux-version;</seg>
  181. <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
  182. </seglistitem>
  183. </segmentedlist>
  184. <variablelist>
  185. <bridgehead renderas="sect3">Short Descriptions</bridgehead>
  186. <?dbfo list-presentation="list"?>
  187. <?dbhtml list-presentation="table"?>
  188. <varlistentry id="config">
  189. <term><filename>config-&linux-version;</filename></term>
  190. <listitem>
  191. <para>Contains all the configuration selections for the kernel</para>
  192. <indexterm zone="ch-bootable-kernel config">
  193. <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
  194. </indexterm>
  195. </listitem>
  196. </varlistentry>
  197. <varlistentry id="lfskernel">
  198. <term><filename>vmlinux-&linux-version;-lfs-&version;</filename></term>
  199. <listitem>
  200. <para>The engine of the Linux system. When turning on the computer,
  201. the kernel is the first part of the operating system that gets loaded.
  202. It detects and initializes all components of the computer's hardware,
  203. then makes these components available as a tree of files to the
  204. software and turns a single CPU into a multitasking machine capable
  205. of running scores of programs seemingly at the same time</para>
  206. <indexterm zone="ch-bootable-kernel lfskernel">
  207. <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
  208. </indexterm>
  209. </listitem>
  210. </varlistentry>
  211. <varlistentry id="System.map">
  212. <term><filename>System.map-&linux-version;</filename></term>
  213. <listitem>
  214. <para>A list of addresses and symbols; it maps the entry points and
  215. addresses of all the functions and data structures in the
  216. kernel</para>
  217. <indexterm zone="ch-bootable-kernel System.map">
  218. <primary sortas="e-/boot/System.map">/boot/System.map-&linux-version;</primary>
  219. </indexterm>
  220. </listitem>
  221. </varlistentry>
  222. </variablelist>
  223. </sect2>
  224. </sect1>