[7152faa] | 1 | <?xml version="1.0" encoding="UTF-8"?>
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[b06ca36] | 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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[673b0d8] | 4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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| 5 | %general-entities;
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| 6 | ]>
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[6a3b6af] | 7 |
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[afcfd74] | 8 | <sect1 id="ch-preps-settingenviron">
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[6a3b6af] | 9 | <?dbhtml filename="settingenvironment.html"?>
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| 10 |
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| 11 | <title>Setting Up the Environment</title>
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[673b0d8] | 12 |
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[6a3b6af] | 13 | <para>Set up a good working environment by creating two new startup files
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| 14 | for the <command>bash</command> shell. While logged in as user
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| 15 | <systemitem class="username">lfs</systemitem>, issue the following command
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| 16 | to create a new <filename>.bash_profile</filename>:</para>
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[81fd230] | 17 |
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[05616e2] | 18 | <screen><userinput>cat > ~/.bash_profile << "EOF"
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[d72e04a] | 19 | <literal>exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash</literal>
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[55851d6] | 20 | EOF</userinput></screen>
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[673b0d8] | 21 |
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[4e26453] | 22 | <para>When logged on as user <systemitem class="username">lfs</systemitem>,
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| 23 | or when switched to the &lfs-user; user using an <command>su</command> command
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| 24 | with the <quote><parameter>-</parameter></quote> option,
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[aa9ade1] | 25 | the initial shell is a <emphasis>login</emphasis> shell which reads
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[6a3b6af] | 26 | the <filename>/etc/profile</filename> of the host (probably containing some
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| 27 | settings and environment variables) and then <filename>.bash_profile</filename>.
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| 28 | The <command>exec env -i.../bin/bash</command> command in the
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| 29 | <filename>.bash_profile</filename> file replaces the running shell with a new
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| 30 | one with a completely empty environment, except for the <envar>HOME</envar>,
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| 31 | <envar>TERM</envar>, and <envar>PS1</envar> variables. This ensures that no
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| 32 | unwanted and potentially hazardous environment variables from the host system
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[4e26453] | 33 | leak into the build environment.</para>
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[81fd230] | 34 |
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[6a3b6af] | 35 | <para>The new instance of the shell is a <emphasis>non-login</emphasis>
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[ec7b0466] | 36 | shell, which does not read, and execute, the contents of the <filename>/etc/profile</filename> or
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[df43be1] | 37 | <filename>.bash_profile</filename> files, but rather reads, and executes, the
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[6a3b6af] | 38 | <filename>.bashrc</filename> file instead. Create the
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| 39 | <filename>.bashrc</filename> file now:</para>
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[81fd230] | 40 |
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[05616e2] | 41 | <screen><userinput>cat > ~/.bashrc << "EOF"
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[d72e04a] | 42 | <literal>set +h
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[673b0d8] | 43 | umask 022
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| 44 | LFS=/mnt/lfs
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| 45 | LC_ALL=POSIX
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[4e82d47] | 46 | LFS_TGT=$(uname -m)-lfs-linux-gnu
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[b454589] | 47 | PATH=/usr/bin
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[a97aa3d] | 48 | if [ ! -L /bin ]; then PATH=/bin:$PATH; fi
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[b454589] | 49 | PATH=$LFS/tools/bin:$PATH
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[df77b24] | 50 | CONFIG_SITE=$LFS/usr/share/config.site
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| 51 | export LFS LC_ALL LFS_TGT PATH CONFIG_SITE</literal>
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[55851d6] | 52 | EOF</userinput></screen>
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[673b0d8] | 53 |
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[df43be1] | 54 | <variablelist>
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[ee714d3] | 55 | <title>The meaning of the settings in <filename>.bashrc</filename></title>
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[df43be1] | 56 |
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| 57 | <varlistentry>
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| 58 | <term><parameter>set +h</parameter></term>
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| 59 | <listitem>
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[6a3b6af] | 60 | <para>The <command>set +h</command> command turns off
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| 61 | <command>bash</command>'s hash function. Hashing is ordinarily a useful
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| 62 | feature—<command>bash</command> uses a hash table to remember the
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[ec7b0466] | 63 | full path to executable files to avoid searching the <envar>PATH</envar>
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[6a3b6af] | 64 | time and again to find the same executable. However, the new tools should
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[ec7b0466] | 65 | be used as soon as they are installed. Switching off the hash function forces
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| 66 | the shell to search the <envar>PATH</envar> whenever a program is to
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[6a3b6af] | 67 | be run. As such, the shell will find the newly compiled tools in
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[490dc153] | 68 | <filename class="directory">$LFS/tools/bin</filename> as soon as they are
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| 69 | available without remembering a previous version of the same program
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| 70 | provided by the host distro, in
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| 71 | <filename class='directory'>/usr/bin</filename> or
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| 72 | <filename class='directory'>/bin</filename>.</para>
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[df43be1] | 73 | </listitem>
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| 74 | </varlistentry>
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[81fd230] | 75 |
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[df43be1] | 76 | <varlistentry>
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| 77 | <term><parameter>umask 022</parameter></term>
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| 78 | <listitem>
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[6a3b6af] | 79 | <para>Setting the user file-creation mask (umask) to 022 ensures that newly
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| 80 | created files and directories are only writable by their owner, but are
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| 81 | readable and executable by anyone (assuming default modes are used by the
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[ea93c11] | 82 | <ulink role='man' url='&man;open.2'>open(2)</ulink> system call, new files
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| 83 | will end up with permission mode 644 and directories with mode 755).</para>
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[df43be1] | 84 | </listitem>
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| 85 | </varlistentry>
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[81fd230] | 86 |
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[df43be1] | 87 | <varlistentry>
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| 88 | <term><parameter>LFS=/mnt/lfs</parameter></term>
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| 89 | <listitem>
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[6a3b6af] | 90 | <para>The <envar>LFS</envar> variable should be set to the chosen mount
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| 91 | point.</para>
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[df43be1] | 92 | </listitem>
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| 93 | </varlistentry>
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[81fd230] | 94 |
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[df43be1] | 95 | <varlistentry>
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| 96 | <term><parameter>LC_ALL=POSIX</parameter></term>
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| 97 | <listitem>
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[6a3b6af] | 98 | <para>The <envar>LC_ALL</envar> variable controls the localization of certain
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| 99 | programs, making their messages follow the conventions of a specified country.
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[448e226] | 100 | Setting <envar>LC_ALL</envar> to <quote>POSIX</quote> or <quote>C</quote>
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| 101 | (the two are equivalent) ensures that everything will work as expected in
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[4e26453] | 102 | the cross-compilation environment.</para>
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[df43be1] | 103 | </listitem>
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| 104 | </varlistentry>
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[81fd230] | 105 |
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[df43be1] | 106 | <varlistentry>
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[2d6ced8] | 107 | <term><parameter>LFS_TGT=$(uname -m)-lfs-linux-gnu</parameter></term>
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[df43be1] | 108 | <listitem>
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[4e82d47] | 109 | <para>The <envar>LFS_TGT</envar> variable sets a non-default, but compatible machine
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[4e26453] | 110 | description for use when building our cross-compiler and linker and when
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| 111 | cross-compiling our temporary toolchain. More information is provided by
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[4e82d47] | 112 | <xref linkend="ch-tools-toolchaintechnotes" role=""/>.</para>
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[df43be1] | 113 | </listitem>
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| 114 | </varlistentry>
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[4e82d47] | 115 |
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[df43be1] | 116 | <varlistentry>
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[b454589] | 117 | <term><parameter>PATH=/usr/bin</parameter></term>
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| 118 | <listitem>
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[ec7b0466] | 119 | <para>Many modern Linux distributions have merged <filename
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[b454589] | 120 | class="directory">/bin</filename> and <filename
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| 121 | class="directory">/usr/bin</filename>. When this is the case, the standard
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[ec7b0466] | 122 | <envar>PATH</envar> variable should be set to <filename
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[b454589] | 123 | class="directory">/usr/bin/</filename> for the <xref
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| 124 | linkend="chapter-temporary-tools"/> environment. When this is not the
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| 125 | case, the following line adds <filename class="directory">/bin</filename>
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| 126 | to the path.</para>
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| 127 | </listitem>
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| 128 | </varlistentry>
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| 129 |
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| 130 | <varlistentry>
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[a97aa3d] | 131 | <term><parameter>if [ ! -L /bin ]; then PATH=/bin:$PATH; fi</parameter></term>
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[b454589] | 132 | <listitem>
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| 133 | <para>If <filename class="directory">/bin</filename> is not a symbolic
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[4e26453] | 134 | link, it must be added to the <envar>PATH</envar> variable.</para>
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[b454589] | 135 | </listitem>
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| 136 | </varlistentry>
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| 137 |
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| 138 | <varlistentry>
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| 139 | <term><parameter>PATH=$LFS/tools/bin:$PATH</parameter></term>
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[df43be1] | 140 | <listitem>
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[efcb393] | 141 | <para>By putting <filename class="directory">$LFS/tools/bin</filename> ahead of the
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[b454589] | 142 | standard <envar>PATH</envar>, the cross-compiler installed at the beginning
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[ee714d3] | 143 | of <xref linkend="chapter-cross-tools"/> is picked up by the shell
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[b454589] | 144 | immediately after its installation. This, combined with turning off hashing,
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[ec7b0466] | 145 | limits the risk that the compiler from the host is used instead of the
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[b454589] | 146 | cross-compiler.</para>
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[df43be1] | 147 | </listitem>
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| 148 | </varlistentry>
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| 149 |
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| 150 | <varlistentry>
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[df77b24] | 151 | <term><parameter>CONFIG_SITE=$LFS/usr/share/config.site</parameter></term>
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| 152 | <listitem>
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| 153 | <para>In <xref linkend="chapter-cross-tools"/> and
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| 154 | <xref linkend="chapter-temporary-tools"/>, if this variable is not set,
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| 155 | <command>configure</command> scripts
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[a2d41cf2] | 156 | may attempt to load configuration items specific to some distributions from
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| 157 | <filename>/usr/share/config.site</filename> on the host system. Override
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| 158 | it to prevent potential contamination from the host.</para>
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[df77b24] | 159 | </listitem>
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| 160 | </varlistentry>
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| 161 |
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| 162 | <varlistentry>
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| 163 | <term><parameter>export ...</parameter></term>
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[df43be1] | 164 | <listitem>
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[4e26453] | 165 | <para>While the preceding commands have set some variables, in order
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[ee714d3] | 166 | to make them visible within any sub-shells, we export them.</para>
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[df43be1] | 167 | </listitem>
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| 168 | </varlistentry>
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| 169 |
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| 170 | </variablelist>
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[81fd230] | 171 |
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[686c88b] | 172 | <important>
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| 173 |
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[4e26453] | 174 | <para>Several commercial distributions add an undocumented instantiation
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[686c88b] | 175 | of <filename>/etc/bash.bashrc</filename> to the initialization of
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[3a38c46] | 176 | <command>bash</command>. This file has the potential to modify the
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| 177 | <systemitem class="username">lfs</systemitem>
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[dbb9122] | 178 | user's environment in ways that can affect the building of critical LFS
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[3a38c46] | 179 | packages. To make sure the <systemitem class="username">lfs</systemitem>
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[c0c616a] | 180 | user's environment is clean, check for the
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[686c88b] | 181 | presence of <filename>/etc/bash.bashrc</filename> and, if present, move it
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[3a38c46] | 182 | out of the way. As the <systemitem class="username">root</systemitem>
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| 183 | user, run:</para>
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[686c88b] | 184 |
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[707c4d3] | 185 | <screen role="nodump"><userinput>[ ! -e /etc/bash.bashrc ] || mv -v /etc/bash.bashrc /etc/bash.bashrc.NOUSE</userinput></screen>
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[686c88b] | 186 |
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[4e26453] | 187 | <para>When the <systemitem class="username">lfs</systemitem>
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| 188 | user is no longer needed (at the beginning of <xref
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| 189 | linkend="chapter-chroot-temporary-tools"/>), you may safely restore
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[c37e846] | 190 | <filename>/etc/bash.bashrc</filename> (if desired).</para>
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[3a38c46] | 191 |
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| 192 | <para>Note that the LFS Bash package we will build in
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| 193 | <xref linkend="ch-system-bash"/> is not configured to load or execute
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| 194 | <filename>/etc/bash.bashrc</filename>, so this file is useless on a
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| 195 | completed LFS system.</para>
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[686c88b] | 196 | </important>
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| 197 |
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[a0a803c] | 198 | <para>
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| 199 | For many modern systems with multiple processors (or cores) the
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| 200 | compilation time for a package can be reduced by performing a "parallel
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| 201 | make" by telling the make program how many processors are available via
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| 202 | a command line option or an environment variable. For instance, an Intel
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| 203 | Core i9-13900K processor has 8 P (performance) cores and
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| 204 | 16 E (efficiency) cores, and a P core can simultaneously run two threads
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| 205 | so each P core are modeled as two logical cores by the Linux kernel.
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| 206 | As the result there are 32 logical cores in total. One obvious way to
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| 207 | use all these logical cores is allowing <command>make</command> to spawn
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| 208 | up to 32 build jobs. This can be done by passing the
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| 209 | <parameter>-j32</parameter> option to <command>make</command>:
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| 210 | </para>
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| 211 |
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| 212 | <screen role='nodump'><userinput>make -j32</userinput></screen>
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| 213 |
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| 214 | <para>
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| 215 | Or set the <envar>MAKEFLAGS</envar> environment variable and its
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| 216 | content will be automatically used by <command>make</command> as
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| 217 | command line options:
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| 218 | </para>
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| 219 |
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| 220 | <screen role='nodump'><userinput>export MAKEFLAGS=-j32</userinput></screen>
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| 221 |
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| 222 | <important>
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| 223 | <para>
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| 224 | Never pass a <parameter>-j</parameter> option without a number to
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| 225 | <command>make</command> or set such an option in
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| 226 | <envar>MAKEFLAGS</envar>. Doing so will allow <command>make</command>
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[6554500] | 227 | to spawn infinite build jobs and cause system stability problems.
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[a0a803c] | 228 | </para>
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| 229 | </important>
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| 230 |
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| 231 | <para>
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| 232 | To use all logical cores available for building packages in
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| 233 | <xref linkend='chapter-cross-tools'/> and
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| 234 | <xref linkend='chapter-temporary-tools'/>, set <envar>MAKEFLAGS</envar>
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| 235 | now in <filename>.bashrc</filename>:
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| 236 | </para>
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| 237 |
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| 238 | <screen><userinput>cat >> ~/.bashrc << "EOF"
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| 239 | <literal>export MAKEFLAGS=-j<replaceable>$(nproc)</replaceable></literal>
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| 240 | EOF</userinput></screen>
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| 241 |
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| 242 | <para>
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| 243 | Replace <replaceable>$(nproc)</replaceable> with the number of logical
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| 244 | cores you want to use if you don't want to use all the logical cores.
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| 245 | </para>
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| 246 |
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[4e26453] | 247 | <para>Finally, to ensure the environment is fully prepared for building the
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[ec7b0466] | 248 | temporary tools, force the <command>bash</command> shell to read
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| 249 | the new user profile:</para>
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[81fd230] | 250 |
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[673b0d8] | 251 | <screen><userinput>source ~/.bash_profile</userinput></screen>
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| 252 |
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| 253 | </sect1>
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