[673b0d8] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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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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[6a3b6af] | 22 | <para>When logged on as user <systemitem class="username">lfs</systemitem>,
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| 23 | the initial shell is usually a <emphasis>login</emphasis> shell which reads
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| 24 | the <filename>/etc/profile</filename> of the host (probably containing some
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| 25 | settings and environment variables) and then <filename>.bash_profile</filename>.
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| 26 | The <command>exec env -i.../bin/bash</command> command in the
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| 27 | <filename>.bash_profile</filename> file replaces the running shell with a new
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| 28 | one with a completely empty environment, except for the <envar>HOME</envar>,
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| 29 | <envar>TERM</envar>, and <envar>PS1</envar> variables. This ensures that no
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| 30 | unwanted and potentially hazardous environment variables from the host system
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| 31 | leak into the build environment. The technique used here achieves the goal of
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| 32 | ensuring a clean environment.</para>
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[81fd230] | 33 |
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[6a3b6af] | 34 | <para>The new instance of the shell is a <emphasis>non-login</emphasis>
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[df43be1] | 35 | shell, which does not read, and execute, the conten of <filename>/etc/profile</filename> or
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| 36 | <filename>.bash_profile</filename> files, but rather reads, and executes, the
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[6a3b6af] | 37 | <filename>.bashrc</filename> file instead. Create the
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| 38 | <filename>.bashrc</filename> file now:</para>
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[81fd230] | 39 |
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[05616e2] | 40 | <screen><userinput>cat > ~/.bashrc << "EOF"
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[d72e04a] | 41 | <literal>set +h
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[673b0d8] | 42 | umask 022
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| 43 | LFS=/mnt/lfs
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| 44 | LC_ALL=POSIX
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[4e82d47] | 45 | LFS_TGT=$(uname -m)-lfs-linux-gnu
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[b454589] | 46 | PATH=/usr/bin
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[a97aa3d] | 47 | if [ ! -L /bin ]; then PATH=/bin:$PATH; fi
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[b454589] | 48 | PATH=$LFS/tools/bin:$PATH
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[4e82d47] | 49 | export LFS LC_ALL LFS_TGT PATH</literal>
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[55851d6] | 50 | EOF</userinput></screen>
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[673b0d8] | 51 |
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[df43be1] | 52 | <variablelist>
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[ee714d3] | 53 | <title>The meaning of the settings in <filename>.bashrc</filename></title>
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[df43be1] | 54 |
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| 55 | <varlistentry>
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| 56 | <term><parameter>set +h</parameter></term>
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| 57 | <listitem>
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[6a3b6af] | 58 | <para>The <command>set +h</command> command turns off
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| 59 | <command>bash</command>'s hash function. Hashing is ordinarily a useful
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| 60 | feature—<command>bash</command> uses a hash table to remember the
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| 61 | full path of executable files to avoid searching the <envar>PATH</envar>
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| 62 | time and again to find the same executable. However, the new tools should
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| 63 | be used as soon as they are installed. By switching off the hash function,
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| 64 | the shell will always search the <envar>PATH</envar> when a program is to
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| 65 | be run. As such, the shell will find the newly compiled tools in
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[d66640e] | 66 | <filename class="directory">$LFS/tools</filename> as soon as they are
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[6a3b6af] | 67 | available without remembering a previous version of the same program in a
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| 68 | different location.</para>
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[df43be1] | 69 | </listitem>
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| 70 | </varlistentry>
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[81fd230] | 71 |
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[df43be1] | 72 | <varlistentry>
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| 73 | <term><parameter>umask 022</parameter></term>
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| 74 | <listitem>
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[6a3b6af] | 75 | <para>Setting the user file-creation mask (umask) to 022 ensures that newly
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| 76 | created files and directories are only writable by their owner, but are
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| 77 | readable and executable by anyone (assuming default modes are used by the
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| 78 | <function>open(2)</function> system call, new files will end up with permission
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| 79 | mode 644 and directories with mode 755).</para>
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[df43be1] | 80 | </listitem>
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| 81 | </varlistentry>
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[81fd230] | 82 |
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[df43be1] | 83 | <varlistentry>
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| 84 | <term><parameter>LFS=/mnt/lfs</parameter></term>
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| 85 | <listitem>
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[6a3b6af] | 86 | <para>The <envar>LFS</envar> variable should be set to the chosen mount
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| 87 | point.</para>
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[df43be1] | 88 | </listitem>
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| 89 | </varlistentry>
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[81fd230] | 90 |
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[df43be1] | 91 | <varlistentry>
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| 92 | <term><parameter>LC_ALL=POSIX</parameter></term>
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| 93 | <listitem>
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[6a3b6af] | 94 | <para>The <envar>LC_ALL</envar> variable controls the localization of certain
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| 95 | programs, making their messages follow the conventions of a specified country.
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[448e226] | 96 | Setting <envar>LC_ALL</envar> to <quote>POSIX</quote> or <quote>C</quote>
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| 97 | (the two are equivalent) ensures that everything will work as expected in
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| 98 | the chroot environment.</para>
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[df43be1] | 99 | </listitem>
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| 100 | </varlistentry>
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[81fd230] | 101 |
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[df43be1] | 102 | <varlistentry>
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| 103 | <term><parameter>LFS_TGT=(uname -m)-lfs-linux-gnu</parameter></term>
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| 104 | <listitem>
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[4e82d47] | 105 | <para>The <envar>LFS_TGT</envar> variable sets a non-default, but compatible machine
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| 106 | description for use when building our cross compiler and linker and when cross
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| 107 | compiling our temporary toolchain. More information is contained in
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| 108 | <xref linkend="ch-tools-toolchaintechnotes" role=""/>.</para>
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[df43be1] | 109 | </listitem>
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| 110 | </varlistentry>
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[4e82d47] | 111 |
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[df43be1] | 112 | <varlistentry>
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[b454589] | 113 | <term><parameter>PATH=/usr/bin</parameter></term>
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| 114 | <listitem>
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| 115 | <para>Many modern linux distributions have merged <filename
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| 116 | class="directory">/bin</filename> and <filename
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| 117 | class="directory">/usr/bin</filename>. When this is the case, the standard
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| 118 | <envar>PATH</envar> variable needs just to be set to <filename
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| 119 | class="directory">/usr/bin/</filename> for the <xref
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| 120 | linkend="chapter-temporary-tools"/> environment. When this is not the
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| 121 | case, the following line adds <filename class="directory">/bin</filename>
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| 122 | to the path.</para>
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| 123 | </listitem>
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| 124 | </varlistentry>
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| 125 |
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| 126 | <varlistentry>
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[a97aa3d] | 127 | <term><parameter>if [ ! -L /bin ]; then PATH=/bin:$PATH; fi</parameter></term>
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[b454589] | 128 | <listitem>
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| 129 | <para>If <filename class="directory">/bin</filename> is not a symbolic
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| 130 | link, then it has to be added to the <envar>PATH</envar> variable.</para>
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| 131 | </listitem>
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| 132 | </varlistentry>
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| 133 |
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| 134 | <varlistentry>
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| 135 | <term><parameter>PATH=$LFS/tools/bin:$PATH</parameter></term>
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[df43be1] | 136 | <listitem>
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[efcb393] | 137 | <para>By putting <filename class="directory">$LFS/tools/bin</filename> ahead of the
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[b454589] | 138 | standard <envar>PATH</envar>, the cross-compiler installed at the beginning
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[ee714d3] | 139 | of <xref linkend="chapter-cross-tools"/> is picked up by the shell
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[b454589] | 140 | immediately after its installation. This, combined with turning off hashing,
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| 141 | limits the risk that the compiler from the host be used instead of the
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| 142 | cross-compiler.</para>
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[df43be1] | 143 | </listitem>
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| 144 | </varlistentry>
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| 145 |
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| 146 | <varlistentry>
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| 147 | <term><parameter>export LFS LC_ALL LFS_TGT PATH</parameter></term>
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| 148 | <listitem>
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| 149 | <para>While the above commands have set some variables, in order
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[ee714d3] | 150 | to make them visible within any sub-shells, we export them.</para>
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[df43be1] | 151 | </listitem>
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| 152 | </varlistentry>
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| 153 |
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| 154 | </variablelist>
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[81fd230] | 155 |
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[686c88b] | 156 | <important>
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| 157 |
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| 158 | <para>Several commercial distributions add a non-documented instantiation
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| 159 | of <filename>/etc/bash.bashrc</filename> to the initialization of
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[3a38c46] | 160 | <command>bash</command>. This file has the potential to modify the
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| 161 | <systemitem class="username">lfs</systemitem>
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[dbb9122] | 162 | user's environment in ways that can affect the building of critical LFS
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[3a38c46] | 163 | packages. To make sure the <systemitem class="username">lfs</systemitem>
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| 164 | user's envronment is clean, check for the
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[686c88b] | 165 | presence of <filename>/etc/bash.bashrc</filename> and, if present, move it
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[3a38c46] | 166 | out of the way. As the <systemitem class="username">root</systemitem>
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| 167 | user, run:</para>
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[686c88b] | 168 |
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[3a38c46] | 169 | <screen role="nodump"><userinput>[ ! -e /etc/bash.bashrc ] || mv -v /etc/bash.bashrc /etc/bash.bashrc.NOUSE</userinput></screen>
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[686c88b] | 170 |
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[ee0638f] | 171 | <para>After use of the <systemitem class="username">lfs</systemitem>
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| 172 | user is finished at the beginning of <xref
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[686c88b] | 173 | linkend="chapter-chroot-temporary-tools"/>, you can restore
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[3a38c46] | 174 | <filename>/etc/bash.bashrc</filename> (if desired).</para>
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| 175 |
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| 176 | <para>Note that the LFS Bash package we will build in
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| 177 | <xref linkend="ch-system-bash"/> is not configured to load or execute
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| 178 | <filename>/etc/bash.bashrc</filename>, so this file is useless on a
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| 179 | completed LFS system.</para>
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[686c88b] | 180 | </important>
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| 181 |
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[6a3b6af] | 182 | <para>Finally, to have the environment fully prepared for building the
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| 183 | temporary tools, source the just-created user profile:</para>
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[81fd230] | 184 |
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[673b0d8] | 185 | <screen><userinput>source ~/.bash_profile</userinput></screen>
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| 186 |
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| 187 | </sect1>
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