1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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5 | %general-entities;
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6 | ]>
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7 |
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8 | <sect1 id="ch-bootable-kernel" role="wrap">
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9 | <?dbhtml filename="kernel.html"?>
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10 |
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11 | <sect1info condition="script">
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12 | <productname>linux</productname>
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13 | <productnumber>&linux-version;</productnumber>
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14 | <address>&linux-url;</address>
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15 | </sect1info>
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16 |
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17 | <title>Linux-&linux-version;</title>
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18 |
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19 | <indexterm zone="ch-bootable-kernel">
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20 | <primary sortas="a-Linux">Linux</primary>
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21 | </indexterm>
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22 |
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23 | <sect2 role="package">
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24 | <title/>
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25 |
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26 | <para>The Linux package contains the Linux kernel.</para>
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27 |
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28 | <segmentedlist>
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29 | <segtitle>&buildtime;</segtitle>
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30 | <segtitle>&diskspace;</segtitle>
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31 |
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32 | <seglistitem>
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33 | <seg>&linux-ch8-sbu;</seg>
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34 | <seg>&linux-ch8-du;</seg>
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35 | </seglistitem>
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36 | </segmentedlist>
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37 |
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38 | </sect2>
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39 |
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40 | <sect2 role="installation">
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41 | <title>Installation of the kernel</title>
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42 |
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43 | <para>Building the kernel involves a few steps—configuration,
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44 | compilation, and installation. Read the <filename>README</filename> file
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45 | in the kernel source tree for alternative methods to the way this book
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46 | configures the kernel.</para>
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47 |
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48 | <para>Prepare for compilation by running the following command:</para>
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49 |
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50 | <screen><userinput remap="pre">make mrproper</userinput></screen>
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51 |
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52 | <para>This ensures that the kernel tree is absolutely clean. The
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53 | kernel team recommends that this command be issued prior to each
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54 | kernel compilation. Do not rely on the source tree being clean after
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55 | un-tarring.</para>
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56 |
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57 | <!-- Support for compiling a keymap into the kernel is deliberately removed -->
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58 |
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59 | <para>Configure the kernel via a menu-driven interface. For general
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60 | information on kernel configuration see <ulink
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61 | url="&hints-root;kernel-configuration.txt"/>. BLFS has some information
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62 | regarding particular kernel configuration requirements of packages outside
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63 | of LFS at <ulink
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64 | url="&blfs-root;view/svn/longindex.html#kernel-config-index"/>. </para>
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65 |
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66 | <note><para>Due to recent changes in <application>udev</application>, be sure to
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67 | select:</para>
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68 |
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69 | <screen role="nodump">Device Drivers --->
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70 | Generic Driver Options --->
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71 | Maintain a devtmpfs filesystem to mount at /dev</screen></note>
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72 |
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73 | <screen role="nodump"><userinput>make LANG=<replaceable><host_LANG_value></replaceable> LC_ALL= menuconfig</userinput></screen>
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74 |
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75 | <variablelist>
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76 | <title>The meaning of the make parameters:</title>
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77 |
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78 | <varlistentry>
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79 | <term><parameter>LANG=<host_LANG_value> LC_ALL=</parameter></term>
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80 | <listitem>
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81 | <para>This establishes the locale setting to the one used on the host.
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82 | This is needed for a proper menuconfig ncurses interface line
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83 | drawing on UTF-8 linux text console.</para>
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84 |
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85 | <para>Be sure to replace <replaceable><host_LANG_value></replaceable>
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86 | by the value of the <envar>$LANG</envar> variable from your host.
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87 | If not set, you could use instead the host's value of <envar>$LC_ALL</envar>
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88 | or <envar>$LC_CTYPE</envar>.</para>
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89 | </listitem>
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90 | </varlistentry>
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91 |
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92 | </variablelist>
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93 |
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94 | <para>Alternatively, <command>make oldconfig</command> may be more
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95 | appropriate in some situations. See the <filename>README</filename>
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96 | file for more information.</para>
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97 |
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98 | <para>If desired, skip kernel configuration by copying the kernel
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99 | config file, <filename>.config</filename>, from the host system
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100 | (assuming it is available) to the unpacked <filename
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101 | class="directory">linux-&linux-version;</filename> directory. However,
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102 | we do not recommend this option. It is often better to explore all the
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103 | configuration menus and create the kernel configuration from
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104 | scratch.</para>
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105 |
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106 | <para>Compile the kernel image and modules:</para>
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107 |
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108 | <screen><userinput remap="make">make</userinput></screen>
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109 |
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110 | <para>If using kernel modules, module configuration in <filename
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111 | class="directory">/etc/modprobe.d</filename> may be required.
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112 | Information pertaining to modules and kernel configuration is
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113 | located in <xref linkend="ch-scripts-udev"/> and in the kernel
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114 | documentation in the <filename
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115 | class="directory">linux-&linux-version;/Documentation</filename> directory.
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116 | Also, <filename>modprobe.conf(5)</filename> may be of interest.</para>
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117 |
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118 | <para>Install the modules, if the kernel configuration uses them:</para>
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119 |
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120 | <screen><userinput remap="install">make modules_install</userinput></screen>
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121 |
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122 | <para>After kernel compilation is complete, additional steps are
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123 | required to complete the installation. Some files need to be copied to
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124 | the <filename class="directory">/boot</filename> directory.</para>
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125 |
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126 | <para>The path to the kernel image may vary depending on the platform being
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127 | used. The filename below can be changed to suit your taste, but the stem of
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128 | the filename should be <emphasis>vmlinuz</emphasis> to be compatible with
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129 | the automatic setup of the boot process described in the next section. The
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130 | following command assumes an x86 architecture:</para>
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131 |
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132 | <screen><userinput remap="install">cp -v arch/x86/boot/bzImage /boot/vmlinuz-&linux-version;-lfs-&version;</userinput></screen>
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133 |
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134 | <para><filename>System.map</filename> is a symbol file for the kernel.
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135 | It maps the function entry points of every function in the kernel API,
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136 | as well as the addresses of the kernel data structures for the running
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137 | kernel. It is used as a resource when investigating kernel problems.
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138 | Issue the following command to install the map file:</para>
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139 |
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140 | <screen><userinput remap="install">cp -v System.map /boot/System.map-&linux-version;</userinput></screen>
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141 |
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142 | <para>The kernel configuration file <filename>.config</filename>
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143 | produced by the <command>make menuconfig</command> step
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144 | above contains all the configuration selections for the kernel
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145 | that was just compiled. It is a good idea to keep this file for future
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146 | reference:</para>
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147 |
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148 | <screen><userinput remap="install">cp -v .config /boot/config-&linux-version;</userinput></screen>
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149 |
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150 | <para>Install the documentation for the Linux kernel:</para>
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151 |
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152 | <screen><userinput remap="install">install -d /usr/share/doc/linux-&linux-version;
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153 | cp -r Documentation/* /usr/share/doc/linux-&linux-version;</userinput></screen>
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154 |
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155 | <para>It is important to note that the files in the kernel source
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156 | directory are not owned by <emphasis>root</emphasis>. Whenever a
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157 | package is unpacked as user <emphasis>root</emphasis> (like we did
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158 | inside chroot), the files have the user and group IDs of whatever
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159 | they were on the packager's computer. This is usually not a problem
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160 | for any other package to be installed because the source tree is
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161 | removed after the installation. However, the Linux source tree is
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162 | often retained for a long time. Because of this, there is a chance
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163 | that whatever user ID the packager used will be assigned to somebody
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164 | on the machine. That person would then have write access to the kernel
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165 | source.</para>
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166 |
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167 | <para>If the kernel source tree is going to be retained, run
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168 | <command>chown -R 0:0</command> on the <filename
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169 | class="directory">linux-&linux-version;</filename> directory to ensure
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170 | all files are owned by user <emphasis>root</emphasis>.</para>
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171 |
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172 | <warning>
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173 | <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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178 | complete.</para>
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179 | </warning>
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180 |
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181 | <warning>
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182 | <para>The headers in the system's
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183 | <filename class="directory">include</filename> directory should
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184 | <emphasis>always</emphasis> be the ones against which Glibc was compiled,
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185 | that is, the sanitised headers from this Linux kernel tarball.
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186 | Therefore, they should <emphasis>never</emphasis> be replaced by either
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187 | the raw kernel headers or any other kernel sanitized headers.</para>
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188 | </warning>
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189 |
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190 | </sect2>
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191 |
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192 | <sect2 id="conf-modprobe" role="configuration">
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193 | <title>Configuring Linux Module Load Order</title>
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194 |
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195 | <indexterm zone="conf-modprobe">
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196 | <primary sortas="e-/etc/modprobe.d/usb.conf">/etc/modprobe.d/usb.conf</primary>
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197 | </indexterm>
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198 |
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199 | <para>The <filename>/etc/modprobe.d/usb.conf</filename> file needs to be
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200 | created so that if the USB drivers (ehci_hcd, ohci_hcd and uhci_hcd) have
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201 | been built as modules, they will be loaded in the correct order; ehci_hcd
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202 | needs to be loaded prior to ohci_hcd and uhci_hcd in order to avoid a
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203 | warning being output at boot time.</para>
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204 |
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205 | <para>Create a new file <filename>/etc/modprobe.d/usb.conf</filename> by running
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206 | the following:</para>
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207 |
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208 | <screen><userinput>install -v -m755 -d /etc/modprobe.d
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209 | cat > /etc/modprobe.d/usb.conf << "EOF"
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210 | <literal># Begin /etc/modprobe.d/usb.conf
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211 |
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212 | install ohci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i ohci_hcd ; true
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213 | install uhci_hcd /sbin/modprobe ehci_hcd ; /sbin/modprobe -i uhci_hcd ; true
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214 |
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215 | # End /etc/modprobe.d/usb.conf</literal>
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216 | EOF</userinput></screen>
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217 |
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218 | </sect2>
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219 |
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220 | <sect2 id="contents-kernel" role="content">
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221 | <title>Contents of Linux</title>
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222 |
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223 | <segmentedlist>
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224 | <segtitle>Installed files</segtitle>
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225 | <segtitle>Installed directories</segtitle>
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226 |
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227 | <seglistitem>
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228 | <seg>config-&linux-version;,
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229 | vmlinux-&linux-version;-lfs-&version;-&linux-version;, and
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230 | System.map-&linux-version;</seg>
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231 | <seg>/lib/modules, /usr/share/doc/linux-&linux-version;</seg>
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232 | </seglistitem>
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233 | </segmentedlist>
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234 |
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235 | <variablelist>
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236 | <bridgehead renderas="sect3">Short Descriptions</bridgehead>
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237 | <?dbfo list-presentation="list"?>
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238 | <?dbhtml list-presentation="table"?>
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239 |
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240 | <varlistentry id="config">
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241 | <term><filename>config-&linux-version;</filename></term>
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242 | <listitem>
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243 | <para>Contains all the configuration selections for the kernel</para>
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244 | <indexterm zone="ch-bootable-kernel config">
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245 | <primary sortas="e-/boot/config">/boot/config-&linux-version;</primary>
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246 | </indexterm>
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247 | </listitem>
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248 | </varlistentry>
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249 |
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250 | <varlistentry id="lfskernel">
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251 | <term><filename>vmlinux-&linux-version;-lfs-&version;</filename></term>
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252 | <listitem>
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253 | <para>The engine of the Linux system. When turning on the computer,
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254 | the kernel is the first part of the operating system that gets loaded.
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255 | It detects and initializes all components of the computer's hardware,
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256 | then makes these components available as a tree of files to the
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257 | software and turns a single CPU into a multitasking machine capable
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258 | of running scores of programs seemingly at the same time</para>
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259 | <indexterm zone="ch-bootable-kernel lfskernel">
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260 | <primary sortas="b-lfskernel">lfskernel-&linux-version;</primary>
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261 | </indexterm>
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262 | </listitem>
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263 | </varlistentry>
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264 |
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265 | <varlistentry id="System.map">
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266 | <term><filename>System.map-&linux-version;</filename></term>
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267 | <listitem>
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268 | <para>A list of addresses and symbols; it maps the entry points and
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269 | addresses of all the functions and data structures in the
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270 | kernel</para>
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271 | <indexterm zone="ch-bootable-kernel System.map">
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272 | <primary sortas="e-/boot/System.map">/boot/System.map-&linux-version;</primary>
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273 | </indexterm>
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274 | </listitem>
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275 | </varlistentry>
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276 |
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277 | </variablelist>
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278 |
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279 | </sect2>
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280 |
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281 | </sect1>
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