[673b0d8] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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| 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN" "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [
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| 3 | <!ENTITY % general-entities SYSTEM "../general.ent">
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| 4 | %general-entities;
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| 5 | ]>
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[a001133] | 6 | <sect1 id="ch-bootable-kernel" xreflabel="Linux" 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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[5888299] | 13 | <para>The Linux package contains the kernel and the header files.</para>
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| 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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| 18 | <seglistitem><seg>All default options: 4.20 SBU</seg>
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| 19 | <seg>All default options: 181 MB</seg></seglistitem>
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| 20 | </segmentedlist>
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| 21 |
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| 22 | <segmentedlist>
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| 23 | <segtitle>Linux installation depends on</segtitle>
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| 24 | <seglistitem><seg>Bash, Binutils, Coreutils, Findutils,
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| 25 | GCC, Glibc, Grep, Gzip, Make, Modutils, Perl, Sed</seg></seglistitem>
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| 26 | </segmentedlist>
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| 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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| 32 | <para>Building the kernel involves a few steps: configuration, compilation, and
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| 33 | installation. If you don't like the way this book configures the kernel, view
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| 34 | the <filename>README</filename> file in the kernel source tree for alternative
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| 35 | methods.</para>
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| 36 |
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| 37 | <para>Prepare for compilation by running the following command:</para>
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| 38 |
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| 39 | <screen><userinput>make mrproper</userinput></screen>
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| 40 |
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| 41 | <para>This ensures that the kernel tree is absolutely clean. The kernel team
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| 42 | recommends that this command be issued prior to <emphasis>each</emphasis>
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| 43 | kernel compilation. You shouldn't rely on the source tree being clean after
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[673b0d8] | 44 | un-tarring.</para>
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[2081905] | 45 |
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[89d204ea] | 46 | <para>Also, ensure that the kernel does not attempt to pass hotplugging events
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[b9e738a] | 47 | to userspace until userspace specifies that it is ready:</para>
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| 48 |
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| 49 | <screen><userinput>sed -i 's@/sbin/hotplug@/bin/true@' kernel/kmod.c</userinput></screen>
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| 50 |
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[89d204ea] | 51 | <para>If, in <xref linkend="ch-scripts-console"/>, you decided you want
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| 52 | to compile the keymap into the kernel, issue the command below:</para>
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| 53 |
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[0c012ac] | 54 | <screen><userinput>loadkeys -m /usr/share/kbd/keymaps/<replaceable>[path to keymap]</replaceable> > \
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[89d204ea] | 55 | <replaceable>[unpacked sources dir]</replaceable>/linux-&linux-version;/drivers/char/defkeymap.c</userinput></screen>
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| 56 |
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| 57 | <para>For example, if you have a Dutch keyboard, you would use
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| 58 | <filename>/usr/share/kbd/keymaps/i386/qwerty/nl.map.gz</filename>.</para>
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| 59 |
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[2081905] | 60 | <para>Configure the kernel via a menu-driven interface:</para>
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| 61 |
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| 62 | <screen><userinput>make menuconfig</userinput></screen>
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| 63 |
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[0c012ac] | 64 | <para><command>make oldconfig</command> may be more appropriate in some
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[2081905] | 65 | situations. See the <filename>README</filename> file for more
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| 66 | information.</para>
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| 67 |
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| 68 | <para>If you wish, you may skip kernel configuration by simply copying the
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| 69 | kernel config file, <filename>.config</filename>, from your host system
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[673b0d8] | 70 | (assuming it is available) to the unpacked <filename class="directory">linux-&linux-version;</filename>
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| 71 | directory. However, we
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[2081905] | 72 | don't recommend this option. You're much better off exploring all the
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| 73 | configuration menus and creating your own kernel configuration from
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| 74 | scratch.</para>
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| 75 |
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| 76 | <para>For POSIX shared memory support, ensure that the kernel config option
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[673b0d8] | 77 | <quote>Virtual memory file system support</quote> is enabled. It resides within
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| 78 | the <quote>File systems</quote> menu and is normally enabled by default.</para>
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[2081905] | 79 |
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[72b0264] | 80 | <para>LFS bootscripts make the assumption that you either compile
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[0c012ac] | 81 | both <quote>Support for Host-side USB</quote> and
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| 82 | <quote>USB device filesystem</quote> directly into the kernel, or don't compile them at
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| 83 | all. Bootscripts will not work properly if it is a module (<filename>usbcore.ko</filename>).</para>
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[72b0264] | 84 |
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[9dfc02f] | 85 | <note><para>NPTL requires the kernel to be compiled with GCC 3.x, in this case
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| 86 | &gcc-version;. Compiling with 2.95.x is known to cause failures in the glibc
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| 87 | testsuite, so do <emphasis>not</emphasis> compile the kernel with gcc 2.95.x
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| 88 | unless you know what you're getting yourself into.</para></note>
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[2081905] | 89 |
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[9dfc02f] | 90 | <para>Compile the kernel image and modules:</para>
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[2081905] | 91 |
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[9dfc02f] | 92 | <screen><userinput>make</userinput></screen>
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[2081905] | 93 |
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[a56c4bb] | 94 | <para>If you intend to use kernel modules, you may need an
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[9dfc02f] | 95 | <filename>/etc/modprobe.conf</filename> file. Information pertaining
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[2081905] | 96 | to modules and to kernel configuration in general may be found in the
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| 97 | kernel documentation, which is found in the
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[0c012ac] | 98 | <filename class="directory">linux-&linux-version;/Documentation</filename> directory.
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| 99 | The modprobe.conf man page
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[a56c4bb] | 100 | <!-- removed for review from tldp.org
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| 101 | and the kernel HOWTO at
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| 102 | <ulink url="http://www.tldp.org/HOWTO/Kernel-HOWTO.html"/> -->
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[0c012ac] | 103 | may also be of interest to you.</para>
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[2081905] | 104 |
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[a56c4bb] | 105 | <para>Be very suspicious while reading other documentation, because it
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| 106 | usually applies to 2.4.x kernels only. As far as the editors know, kernel
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| 107 | configuration issues specific to Hotplug and Udev
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| 108 | are documented nowhere. The problem is that Udev will create a device node
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| 109 | only if Hotplug or a user-written script inserts the corresponding module
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| 110 | into the kernel, and not all modules are detectable by Hotplug. Note
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| 111 | that statements like
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| 112 | <screen>alias char-major-XXX some-module</screen>
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| 113 | in <filename>/etc/modprobe.conf</filename> file don't work with
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| 114 | Udev, and other aliases are often unnecessary with Hotplug.</para>
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| 115 |
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| 116 | <para>Because of all those compilcations with Hotplug, Udev and modules, we
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| 117 | strongly recommend you to start with a completely non-modular kernel
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| 118 | configuration, especially if this is the first time you use Udev.</para>
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| 119 |
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| 120 | <para>Install the modules, if your kernel configuration uses them:</para>
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[2081905] | 121 |
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[9dfc02f] | 122 | <screen><userinput>make modules_install</userinput></screen>
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[2081905] | 123 |
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[b157558] | 124 | <para>If you have a lot of modules and very little space, you may want to
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| 125 | consider stripping and compressing the modules. For most people such compression
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| 126 | isn't worth the trouble, but if you're really pressed for space, then have a look at
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| 127 | <ulink url="http://www.linux-mips.org/archives/linux-mips/2002-04/msg00031.html"/>.</para>
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| 128 |
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[2081905] | 129 | <para>Kernel compilation has finished but more steps are required to complete
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[0c012ac] | 130 | the installation. Some files need to be copied to the <filename class="directory">/boot</filename>
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[2081905] | 131 | directory.</para>
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| 132 |
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| 133 | <para>The path to the kernel image may vary depending on the platform you're
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| 134 | using. Issue the following command to install the kernel:</para>
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| 135 |
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[9dfc02f] | 136 | <screen><userinput>cp arch/i386/boot/bzImage /boot/lfskernel-&linux-version;</userinput></screen>
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[2081905] | 137 |
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| 138 | <para><filename>System.map</filename> is a symbol file for the kernel. It maps
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[673b0d8] | 139 | the function entry points of every function in the kernel API (Application Programming Interface), as well as the
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[2081905] | 140 | addresses of the kernel data structures for the running kernel. Issue the
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| 141 | following command to install the map file:</para>
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| 142 |
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[9dfc02f] | 143 | <screen><userinput>cp System.map /boot/System.map-&linux-version;</userinput></screen>
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[2081905] | 144 |
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| 145 | <para><filename>.config</filename> is the kernel configuration file that was
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| 146 | produced by the <command>make menuconfig</command> step above. It contains all
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| 147 | the config selections for the kernel that was just compiled. It's a good idea
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| 148 | to keep this file for future reference:</para>
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| 149 |
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[9dfc02f] | 150 | <screen><userinput>cp .config /boot/config-&linux-version;</userinput></screen>
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[2081905] | 151 |
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| 152 | <para>It is important to note that the files in the kernel source directory are
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| 153 | not owned by <emphasis>root</emphasis>. Whenever you unpack a package as user
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| 154 | <emphasis>root</emphasis> (like we did here inside chroot), the files end up
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| 155 | having the user and group IDs of whatever they were on the packager's computer.
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| 156 | This is usually not a problem for any other package you install because you
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| 157 | remove the source tree after the installation. But the Linux source tree is
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| 158 | often kept around for a long time, so there's a chance that whatever user ID
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| 159 | the packager used will be assigned to somebody on your machine and then that
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| 160 | person would have write access to the kernel source.</para>
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| 161 |
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| 162 | <para>If you are going to keep the kernel source tree around, you may want to
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[0c012ac] | 163 | run <command>chown -R 0:0</command> on the
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| 164 | <filename class="directory">linux-&linux-version;</filename> directory to ensure all files are
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[2081905] | 165 | owned by user <emphasis>root</emphasis>.</para>
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| 166 |
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| 167 | </sect2>
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[6910868] | 168 |
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[673b0d8] | 169 |
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[c6cb3aa] | 170 | <sect2 id="contents-kernel" role="content"><title>Contents of Linux</title>
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[673b0d8] | 171 |
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[c6cb3aa] | 172 | <segmentedlist>
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| 173 | <segtitle>Installed files</segtitle>
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| 174 | <seglistitem><seg>the kernel, the kernel headers,
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| 175 | and the System.map</seg></seglistitem>
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| 176 | </segmentedlist>
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[673b0d8] | 177 |
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[c6cb3aa] | 178 | <variablelist><title>Short descriptions</title>
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[673b0d8] | 179 |
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[b8a819f] | 180 | <varlistentry id="kernel">
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| 181 | <term>The <emphasis>kernel</emphasis></term>
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[c6cb3aa] | 182 | <listitem>
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[673b0d8] | 183 | <indexterm zone="ch-bootable-kernel kernel"><primary sortas="b-kernel">kernel</primary></indexterm>
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[3966ace] | 184 | <para>is the engine of your Linux system.
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[673b0d8] | 185 | When switching on your box, the kernel is the first part of your operating
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| 186 | system that gets loaded. It detects and initializes all the components of your
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| 187 | computer's hardware, then makes these components available as a tree of files
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| 188 | to the software, and turns a single CPU into a multi-tasking machine capable
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| 189 | of running scores of programs seemingly at the same time.</para>
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[c6cb3aa] | 190 | </listitem>
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| 191 | </varlistentry>
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[673b0d8] | 192 |
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[b8a819f] | 193 | <varlistentry id="kernel-headers">
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| 194 | <term>The <emphasis>kernel headers</emphasis></term>
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[c6cb3aa] | 195 | <listitem>
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[673b0d8] | 196 | <indexterm zone="ch-bootable-kernel kernel-headers"><primary sortas="e-kernel-headers">kernel headers</primary></indexterm>
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[c6cb3aa] | 197 | <para>define the interface to the
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[673b0d8] | 198 | services that the kernel provides. The headers in your system's
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[0c012ac] | 199 | <filename class="directory">include</filename> directory should <emphasis>always</emphasis> be
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[673b0d8] | 200 | the ones against which Glibc was compiled and should therefore
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| 201 | <emphasis>not</emphasis> be replaced when upgrading the kernel.</para>
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[c6cb3aa] | 202 | </listitem>
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| 203 | </varlistentry>
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[673b0d8] | 204 |
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[b8a819f] | 205 | <varlistentry id="System.map">
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| 206 | <term><filename>System.map</filename></term>
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[c6cb3aa] | 207 | <listitem>
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[673b0d8] | 208 | <indexterm zone="ch-bootable-kernel System.map"><primary sortas="e-/boot/System.map">/boot/System.map</primary></indexterm>
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[c6cb3aa] | 209 | <para>is a list of addresses and symbols. It maps the entry points and addresses
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| 210 | of all the functions and data structures in the kernel.</para>
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| 211 | </listitem>
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| 212 | </varlistentry>
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| 213 | </variablelist>
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[673b0d8] | 214 |
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| 215 | </sect2>
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| 216 |
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[6370fa6] | 217 | </sect1>
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