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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6 | <sect1 id="ch-bootable-kernel" xreflabel="Linux" role="wrap">
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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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11 |
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12 | <sect2 role="package"><title/>
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13 | <para>The Linux package contains the kernel and the header files.</para>
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14 |
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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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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,
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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 alternative methods to the way this
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35 | book configures the kernel.</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
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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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45 |
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46 | <para>Also, ensure that the kernel does not attempt to pass
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47 | hotplugging events to userspace until userspace specifies that it is
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48 | ready:</para>
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49 |
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50 | <screen><userinput>sed -i 's@/sbin/hotplug@/bin/true@' kernel/kmod.c</userinput></screen>
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51 |
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52 | <para>If, in <xref linkend="ch-scripts-console"/>, you decided to
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53 | compile the keymap into the kernel, issue the command below:</para>
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54 |
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55 | <screen><userinput>loadkeys -m /usr/share/kbd/keymaps/<replaceable>[path to keymap]</replaceable> > \
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56 | <replaceable>[unpacked sources dir]</replaceable>/linux-&linux-version;/drivers/char/defkeymap.c</userinput></screen>
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57 |
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58 | <para>For example, if using a Dutch keyboard, use
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59 | <filename>/usr/share/kbd/keymaps/i386/qwerty/nl.map.gz</filename>.</para>
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60 |
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61 | <para>Configure the kernel via a menu-driven interface:</para>
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62 |
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63 | <screen><userinput>make menuconfig</userinput></screen>
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64 |
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65 | <para><command>make oldconfig</command> may be more appropriate in some
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66 | situations. See the <filename>README</filename> file for more
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67 | information.</para>
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68 |
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69 | <note><para>When you configure the kernel, be sure to enable the
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70 | <quote>Support for hot-pluggable devices</quote> option under the
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71 | <quote>General Setup</quote> menu. This enables hotplug events that
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72 | are used by <command>udev</command> to populate the <filename
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73 | class="directory">/dev</filename> directory with device
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74 | nodes.</para></note>
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75 |
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76 | <para>If desired, skip kernel configuration by copying the kernel
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77 | config file, <filename>.config</filename>, from the host system
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78 | (assuming it is available) to the unpacked <filename
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79 | class="directory">linux-&linux-version;</filename> directory. However,
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80 | we do not recommend this option. It is often better to explore all the
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81 | configuration menus and creating the kernel configuration from
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82 | scratch.</para>
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83 |
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84 | <para>For POSIX shared memory support, ensure that the kernel config
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85 | option <quote>Virtual memory file system support</quote> is enabled.
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86 | It resides within the <quote>File systems</quote> menu and is normally
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87 | enabled by default.</para>
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88 |
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89 | <para>LFS bootscripts make the assumption that either both
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90 | <quote>Support for Host-side USB</quote> and <quote>USB device
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91 | filesystem</quote> have been compiled directly into the kernel, or
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92 | that neither is compiled at all. Bootscripts will not work properly
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93 | if it is a module (usbcore.ko).</para>
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94 |
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95 | <note><para>NPTL requires the kernel to be compiled with GCC 3.x, in
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96 | this case &gcc-version;. Compiling with 2.95.x is known to cause failures in
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97 | the glibc testsuite, so it is not recommended to compile the kernel
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98 | with gcc 2.95.x.</para></note>
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99 |
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100 | <para>Compile the kernel image and modules:</para>
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101 |
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102 | <screen><userinput>make</userinput></screen>
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103 |
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104 | <para>If using kernel modules, an
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105 | <filename>/etc/modprobe.conf</filename> file may be needed.
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106 | Information pertaining to modules and to kernel configuration is
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107 | located in the kernel documentation in the <filename
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108 | class="directory">linux-&linux-version;/Documentation</filename>
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109 | directory. The <emphasis>modprobe.conf</emphasis> man page may also be
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110 | of interest.</para>
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111 |
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112 | <para>Be very careful when reading other documentation, because it
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113 | usually applies to 2.4.x kernels only. As far as we know, kernel
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114 | configuration issues specific to Hotplug and Udev are not documented.
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115 | The problem is that Udev will create a device node only if Hotplug or
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116 | a user-written script inserts the corresponding module into the
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117 | kernel, and not all modules are detectable by Hotplug. Note that
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118 | statements like <screen>alias char-major-XXX some-module</screen> in
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119 | the <filename>/etc/modprobe.conf</filename> file do not work with
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120 | Udev, and other aliases are often unnecessary with Hotplug.</para>
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121 |
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122 | <para>Because of the complications with Hotplug, Udev, and modules, we
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123 | strongly recommend starting with a completely non-modular kernel
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124 | configuration, especially if this is the first time using Udev.</para>
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125 |
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126 | <para>Install the modules, if your kernel configuration uses them:</para>
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127 |
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128 | <screen><userinput>make modules_install</userinput></screen>
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129 |
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130 | <para>If there are many modules and very little space, consider
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131 | stripping and compressing the modules. For most users, such
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132 | compression is not worth the time, but if the system is pressed for
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133 | space, see <ulink
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134 | url="http://www.linux-mips.org/archives/linux-mips/2002-04/msg00031.html"/>.</para>
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135 |
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136 | <para>After kernel compilation is complete, additional steps are
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137 | required to complete the installation. Some files need to be copied to
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138 | the <filename class="directory">/boot</filename> directory.</para>
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139 |
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140 | <para>The path to the kernel image may vary depending on the platform
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141 | being used. Issue the following command to install the kernel:</para>
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142 |
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143 | <screen><userinput>cp arch/i386/boot/bzImage /boot/lfskernel-&linux-version;</userinput></screen>
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144 |
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145 | <para><filename>System.map</filename> is a symbol file for the kernel.
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146 | It maps the function entry points of every function in the kernel API,
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147 | as well as the addresses of the kernel data structures for the running
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148 | kernel. Issue the following command to install the map file:</para>
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149 |
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150 | <screen><userinput>cp System.map /boot/System.map-&linux-version;</userinput></screen>
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151 |
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152 | <para><filename>.config</filename> is the kernel's configuration file
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153 | that was produced by the <command>make menuconfig</command> step
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154 | above. It contains all the configuration selections for the kernel
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155 | that was just compiled. It is a good idea to keep this file for future
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156 | reference:</para>
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157 |
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158 | <screen><userinput>cp .config /boot/config-&linux-version;</userinput></screen>
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159 |
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160 | <para>It is important to note that the files in the kernel source
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161 | directory are not owned by <emphasis>root</emphasis>. Whenever a
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162 | package is unpacked as user <emphasis>root</emphasis> (like we did
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163 | here inside chroot), the files have the user and group IDs of whatever
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164 | they were on the packager's computer. This is usually not a problem
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165 | for any other package to be installed because the source tree is
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166 | removed after the installation. However, the Linux source tree is
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167 | often retained for a long time. Because of this, there is a chance
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168 | that whatever user ID the packager used will be assigned to somebody
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169 | on the machine. That person would then have write access to the kernel
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170 | source.</para>
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171 |
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172 | <para>If the kernel source tree is going to retained, run
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173 | <command>chown -R 0:0</command> on the <filename
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174 | class="directory">linux-&linux-version;</filename> directory to ensure
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175 | all files are owned by user <emphasis>root</emphasis>.</para>
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176 | </sect2>
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177 |
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178 |
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179 | <sect2 id="contents-kernel" role="content"><title>Contents of Linux</title>
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180 |
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181 | <segmentedlist>
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182 | <segtitle>Installed files</segtitle>
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183 | <seglistitem><seg>the kernel, the kernel headers,
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184 | and the System.map</seg></seglistitem>
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185 | </segmentedlist>
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186 |
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187 | <variablelist><bridgehead renderas="sect3">Short descriptions</bridgehead>
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188 | <?dbfo list-presentation="list"?>
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189 |
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190 | <varlistentry id="kernel">
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191 | <term>The <emphasis>kernel</emphasis></term>
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192 | <listitem>
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193 | <para>the engine of the Linux system. When turning on your computer,
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194 | the kernel is the first part of the operating system that gets loaded.
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195 | It detects and initializes all components of the computer's hardware,
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196 | then makes these components available as a tree of files to the
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197 | software, and turns a single CPU into a multitasking machine capable
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198 | of running scores of programs seemingly at the same time.</para>
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199 | <indexterm zone="ch-bootable-kernel kernel"><primary sortas="b-kernel">kernel</primary></indexterm>
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200 | </listitem>
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201 | </varlistentry>
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202 |
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203 | <varlistentry id="kernel-headers">
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204 | <term>The <emphasis>kernel headers</emphasis></term>
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205 | <listitem>
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206 | <para>defines the interface to the services that the kernel provides.
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207 | The headers in your system's <filename
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208 | class="directory">include</filename> directory should
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209 | <emphasis>always</emphasis> be the ones against which Glibc was
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210 | compiled and therefore, should <emphasis>not</emphasis> be replaced
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211 | when upgrading the kernel.</para>
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212 | <indexterm zone="ch-bootable-kernel kernel-headers"><primary sortas="e-kernel-headers">kernel headers</primary></indexterm>
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213 | </listitem>
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214 | </varlistentry>
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215 |
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216 | <varlistentry id="System.map">
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217 | <term><filename>System.map</filename></term>
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218 | <listitem>
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219 | <para>is a list of addresses and symbols. It maps the entry points and
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220 | addresses of all the functions and data structures in the
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221 | kernel.</para>
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222 | <indexterm zone="ch-bootable-kernel System.map"><primary sortas="e-/boot/System.map">/boot/System.map</primary></indexterm>
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223 | </listitem>
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224 | </varlistentry>
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225 | </variablelist>
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226 |
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227 | </sect2>
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228 |
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229 | </sect1>
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230 |
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