[673b0d8] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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[1770019] | 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN" "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
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[673b0d8] | 3 | <!ENTITY % general-entities SYSTEM "../general.ent">
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| 4 | %general-entities;
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| 5 | ]>
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[81fd230] | 6 | <sect1 id="ch-bootable-kernel" role="wrap">
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[673b0d8] | 7 | <title>Linux-&linux-version;</title>
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| 8 | <?dbhtml filename="kernel.html"?>
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| 9 |
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| 10 | <indexterm zone="ch-bootable-kernel"><primary sortas="a-Linux">Linux</primary></indexterm>
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[6370fa6] | 11 |
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[a001133] | 12 | <sect2 role="package"><title/>
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[81fd230] | 13 | <para>The Linux package contains the kernel and the header files.</para>
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[5888299] | 14 |
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[a001133] | 15 | <segmentedlist>
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| 16 | <segtitle>&buildtime;</segtitle>
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| 17 | <segtitle>&diskspace;</segtitle>
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[81fd230] | 18 | <seglistitem><seg>4.20 SBU</seg>
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| 19 | <seg>181 MB</seg></seglistitem>
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[a001133] | 20 | </segmentedlist>
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| 21 |
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[81fd230] | 22 | <segmentedlist>
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[45992ae] | 23 | <segtitle>&dependencies;</segtitle>
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[81fd230] | 24 | <seglistitem><seg>Bash, Binutils, Coreutils, Findutils,
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| 25 | GCC, Glibc, Grep, Gzip, Make, Modutils, Perl, and Sed</seg></seglistitem>
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| 26 | </segmentedlist>
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[a001133] | 27 | </sect2>
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| 28 |
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| 29 | <sect2 role="installation">
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[2081905] | 30 | <title>Installation of the kernel</title>
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| 31 |
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[81fd230] | 32 | <para>Building the kernel involves a few steps—configuration,
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| 33 | compilation, and installation. Read the <filename>README</filename>
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| 34 | file in the kernel source tree for alternate methods to the way this
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| 35 | book configures the kernel.</para>
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| 36 |
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[1d609dce] | 37 | <para>Prepare for compilation by running the following command:</para>
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[b9e738a] | 38 |
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[1d609dce] | 39 | <screen><userinput>make mrproper</userinput></screen>
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[b9e738a] | 40 |
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[81fd230] | 41 | <para>This ensures that the kernel tree is absolutely clean. The
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| 42 | kernel team recommends that this command be issued prior to each
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| 43 | kernel compilation. Do not rely on the source tree being clean after
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| 44 | un-tarring.</para>
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[d72e04a] | 45 |
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[81fd230] | 46 | <para>If, in <xref linkend="ch-scripts-console" role=","/> it was decided to
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| 47 | compile the keymap into the kernel, issue the command below:</para>
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[89d204ea] | 48 |
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[0c012ac] | 49 | <screen><userinput>loadkeys -m /usr/share/kbd/keymaps/<replaceable>[path to keymap]</replaceable> > \
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[d72e04a] | 50 | drivers/char/defkeymap.c</userinput></screen>
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[89d204ea] | 51 |
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[81fd230] | 52 | <para>For example, if using a Dutch keyboard, use
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[845846e0] | 53 | <filename>/usr/share/kbd/keymaps/i386/qwerty/nl.map.gz</filename>.</para>
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[81fd230] | 54 |
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[b261062] | 55 | <para>Configure the kernel via a menu-driven interface. BLFS has some
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[f134e88] | 56 | information regarding particular kernel configuration requirements of
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[d2f9350] | 57 | packages outside of LFS at <ulink
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[f134e88] | 58 | url="&blfs-root;view/svn/longindex.html#kernel-config-index"/>:</para>
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[2081905] | 59 |
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| 60 | <screen><userinput>make menuconfig</userinput></screen>
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| 61 |
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[81fd230] | 62 | <para>Alternatively, <command>make oldconfig</command> may be more appropriate in some
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| 63 | situations. See the <filename>README</filename> file for more
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| 64 | information.</para>
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| 65 |
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[2ec0d20] | 66 | <note><para>When configuring the kernel, be sure to enable the <quote>Support
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| 67 | for hot-pluggable devices</quote> option under the <quote>General Setup</quote>
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| 68 | menu. This enables hotplug events that are used by <command>udev</command> to
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| 69 | populate the <filename class="directory">/dev</filename> directory with device
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| 70 | nodes. Likewise, enable the <quote>Virtual memory file system support</quote>
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| 71 | option under the <quote>File systems</quote>/<quote>Pseudo filesystems</quote>
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| 72 | menu. This enables the virtual filesystem that the <filename
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| 73 | class="directory">/dev</filename> directory will be mounted on.</para></note>
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[81fd230] | 74 |
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| 75 | <para>If desired, skip kernel configuration by copying the kernel
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| 76 | config file, <filename>.config</filename>, from the host system
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| 77 | (assuming it is available) to the unpacked <filename
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| 78 | class="directory">linux-&linux-version;</filename> directory. However,
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| 79 | we do not recommend this option. It is often better to explore all the
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| 80 | configuration menus and create the kernel configuration from
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| 81 | scratch.</para>
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| 82 |
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[1012ef9] | 83 | <para>LFS Bootscripts make the assumption that both <quote>Support for Host-side
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| 84 | USB</quote> and <quote>USB device filesystem</quote> have been compiled directly
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| 85 | into the kernel, or that neither is compiled at all. The bootscripts will not
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| 86 | work properly if <quote>Host-side USB</quote> is compiled as a module
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| 87 | (usbcore.ko).</para>
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[81fd230] | 88 |
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[741921c] | 89 | <note><para>NPTL requires the kernel to be compiled with GCC 3.x, in
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| 90 | this case &gcc-version;. Compiling with 2.95.x is known to cause failures in
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| 91 | the glibc test suite, so it is not recommended to compile the kernel
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| 92 | with gcc 2.95.x.</para></note>
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| 93 |
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[9dfc02f] | 94 | <para>Compile the kernel image and modules:</para>
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[2081905] | 95 |
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[9dfc02f] | 96 | <screen><userinput>make</userinput></screen>
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[2081905] | 97 |
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[81fd230] | 98 | <para>If using kernel modules, an
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| 99 | <filename>/etc/modprobe.conf</filename> file may be needed.
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| 100 | Information pertaining to modules and kernel configuration is
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| 101 | located in the kernel documentation in the <filename
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| 102 | class="directory">linux-&linux-version;/Documentation</filename>
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| 103 | directory. The <emphasis>modprobe.conf</emphasis> man page may also be
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| 104 | of interest.</para>
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| 105 |
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| 106 | <para>Be very careful when reading other documentation because it
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| 107 | usually applies to 2.4.x kernels only. As far as we know, kernel
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| 108 | configuration issues specific to Hotplug and Udev are not documented.
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| 109 | The problem is that Udev will create a device node only if Hotplug or
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| 110 | a user-written script inserts the corresponding module into the
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| 111 | kernel, and not all modules are detectable by Hotplug. Note that
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| 112 | statements like the one below in the
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| 113 | <filename>/etc/modprobe.conf</filename> file do not work with
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| 114 | Udev:</para>
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| 115 |
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| 116 | <para><screen>alias char-major-XXX some-module</screen></para>
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| 117 |
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| 118 | <para>Because of the complications with Hotplug, Udev, and modules, we
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| 119 | strongly recommend starting with a completely non-modular kernel
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| 120 | configuration, especially if this is the first time using Udev.</para>
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| 121 |
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| 122 | <para>Install the modules, if the kernel configuration uses them:</para>
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[2081905] | 123 |
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[9dfc02f] | 124 | <screen><userinput>make modules_install</userinput></screen>
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[2081905] | 125 |
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[81fd230] | 126 | <para>If there are many modules and very little space, consider
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| 127 | stripping and compressing the modules. For most users, such
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| 128 | compression is not worth the time, but if the system is pressed for
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| 129 | space, see <ulink
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| 130 | url="http://www.linux-mips.org/archives/linux-mips/2002-04/msg00031.html"/>.</para>
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| 131 |
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| 132 | <para>After kernel compilation is complete, additional steps are
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| 133 | required to complete the installation. Some files need to be copied to
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| 134 | the <filename class="directory">/boot</filename> directory.</para>
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| 135 |
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| 136 | <para>The path to the kernel image may vary depending on the platform
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[2ec0d20] | 137 | being used. The following command assumes an x86 architecture:</para>
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[2081905] | 138 |
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[9dfc02f] | 139 | <screen><userinput>cp arch/i386/boot/bzImage /boot/lfskernel-&linux-version;</userinput></screen>
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[2081905] | 140 |
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[81fd230] | 141 | <para><filename>System.map</filename> is a symbol file for the kernel.
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| 142 | It maps the function entry points of every function in the kernel API,
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| 143 | as well as the addresses of the kernel data structures for the running
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| 144 | kernel. Issue the following command to install the map file:</para>
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| 145 |
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[9dfc02f] | 146 | <screen><userinput>cp System.map /boot/System.map-&linux-version;</userinput></screen>
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[2081905] | 147 |
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[81fd230] | 148 | <para>The kernel configuration file <filename>.config</filename>
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| 149 | produced by the <command>make menuconfig</command> step
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| 150 | above contains all the configuration selections for the kernel
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| 151 | that was just compiled. It is a good idea to keep this file for future
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| 152 | reference:</para>
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| 153 |
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[9dfc02f] | 154 | <screen><userinput>cp .config /boot/config-&linux-version;</userinput></screen>
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[2081905] | 155 |
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[81fd230] | 156 | <para>It is important to note that the files in the kernel source
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| 157 | directory are not owned by <emphasis>root</emphasis>. Whenever a
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| 158 | package is unpacked as user <emphasis>root</emphasis> (like we did
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| 159 | inside chroot), the files have the user and group IDs of whatever
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| 160 | they were on the packager's computer. This is usually not a problem
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| 161 | for any other package to be installed because the source tree is
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| 162 | removed after the installation. However, the Linux source tree is
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| 163 | often retained for a long time. Because of this, there is a chance
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| 164 | that whatever user ID the packager used will be assigned to somebody
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| 165 | on the machine. That person would then have write access to the kernel
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| 166 | source.</para>
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| 167 |
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| 168 | <para>If the kernel source tree is going to be retained, run
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| 169 | <command>chown -R 0:0</command> on the <filename
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| 170 | class="directory">linux-&linux-version;</filename> directory to ensure
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| 171 | all files are owned by user <emphasis>root</emphasis>.</para>
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| 172 |
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| 173 | <warning><para>Some kernel documentation recommends creating a symlink from
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| 174 | <filename class="symlink">/usr/src/linux</filename> pointing to the kernel
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| 175 | source directory. This is specific to kernels prior to the 2.6 series and
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| 176 | <emphasis>must not</emphasis> be created on an LFS system as it can cause
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| 177 | problems for packages you may wish to build once your base LFS system is
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[d2f9350] | 178 | complete.</para>
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| 179 |
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| 180 | <para>Also, the headers in the system's
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| 181 | <filename class="directory">include</filename> directory should
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| 182 | <emphasis>always</emphasis> be the ones against which Glibc was compiled,
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| 183 | that is, the ones from the Linux-Libc-Headers package, and therefore, should
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| 184 | <emphasis>never</emphasis> be replaced by the kernel headers.</para></warning>
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[2081905] | 185 |
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| 186 | </sect2>
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[6910868] | 187 |
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[673b0d8] | 188 |
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[c6cb3aa] | 189 | <sect2 id="contents-kernel" role="content"><title>Contents of Linux</title>
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[673b0d8] | 190 |
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[81fd230] | 191 | <segmentedlist>
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| 192 | <segtitle>Installed files</segtitle>
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[d2f9350] | 193 | <seglistitem><seg>config-&linux-version;, lfskernel-&linux-version;,
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| 194 | and System.map-&linux-version;</seg></seglistitem>
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[81fd230] | 195 | </segmentedlist>
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| 196 |
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| 197 | <variablelist><bridgehead renderas="sect3">Short Descriptions</bridgehead>
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| 198 | <?dbfo list-presentation="list"?>
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[8f97096] | 199 | <?dbhtml list-presentation="table"?>
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[81fd230] | 200 |
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[d2f9350] | 201 | <varlistentry id="config">
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| 202 | <term><filename>config-&linux-version;</filename></term>
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| 203 | <listitem>
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| 204 | <para>Contains all the configuration selections for the kernel</para>
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| 205 | <indexterm zone="ch-bootable-kernel config"><primary sortas="e-/boot/config">/boot/config-&linux-version;</primary></indexterm>
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| 206 | </listitem>
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| 207 | </varlistentry>
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| 208 |
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| 209 | <varlistentry id="lfskernel">
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| 210 | <term><filename>lfskernel-&linux-version;</filename></term>
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[81fd230] | 211 | <listitem>
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| 212 | <para>The engine of the Linux system. When turning on the computer,
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| 213 | the kernel is the first part of the operating system that gets loaded.
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| 214 | It detects and initializes all components of the computer's hardware,
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| 215 | then makes these components available as a tree of files to the
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| 216 | software and turns a single CPU into a multitasking machine capable
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[d2f9350] | 217 | of running scores of programs seemingly at the same time</para>
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[8ccf66e1] | 218 | <indexterm zone="ch-bootable-kernel lfskernel"><primary sortas="b-lfskernel">lfskernel-&linux-version;</primary></indexterm>
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[81fd230] | 219 | </listitem>
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| 220 | </varlistentry>
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| 221 |
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| 222 | <varlistentry id="System.map">
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[d2f9350] | 223 | <term><filename>System.map-&linux-version;</filename></term>
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[81fd230] | 224 | <listitem>
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| 225 | <para>A list of addresses and symbols; it maps the entry points and
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| 226 | addresses of all the functions and data structures in the
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| 227 | kernel</para>
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[d2f9350] | 228 | <indexterm zone="ch-bootable-kernel System.map"><primary sortas="e-/boot/System.map">/boot/System.map-&linux-version;</primary></indexterm>
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[81fd230] | 229 | </listitem>
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| 230 | </varlistentry>
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| 231 | </variablelist>
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[673b0d8] | 232 |
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| 233 | </sect2>
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| 234 |
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[6370fa6] | 235 | </sect1>
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