[1fa2099] | 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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[ede49cd] | 8 | <sect1 id="ch-preps-settingenviron">
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[1fa2099] | 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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| 12 |
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| 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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| 17 |
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| 18 | <screen><userinput>cat > ~/.bash_profile << "EOF"
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| 19 | <literal>exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash</literal>
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| 20 | EOF</userinput></screen>
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| 21 |
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| 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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| 33 |
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| 34 | <para>The new instance of the shell is a <emphasis>non-login</emphasis>
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[a1ad522] | 35 | shell, which does not read, and execute, the contents of <filename>/etc/profile</filename> or
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[88ec930] | 36 | <filename>.bash_profile</filename> files, but rather reads, and executes, the
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[1fa2099] | 37 | <filename>.bashrc</filename> file instead. Create the
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| 38 | <filename>.bashrc</filename> file now:</para>
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| 39 |
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[8eb3fe4] | 40 | <screen arch="default"><userinput>cat > ~/.bashrc << "EOF"
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[1fa2099] | 41 | <literal>set +h
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| 42 | umask 022
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| 43 | LFS=/mnt/lfs
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| 44 | LC_ALL=POSIX
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| 45 | LFS_TGT=$(uname -m)-lfs-linux-gnu
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[37e35d2] | 46 | PATH=/usr/bin
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| 47 | if [ ! -L /bin ]; then PATH=/bin:$PATH; fi
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| 48 | PATH=$LFS/tools/bin:$PATH
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[1fa2099] | 49 | export LFS LC_ALL LFS_TGT PATH</literal>
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[8eb3fe4] | 50 | EOF</userinput></screen>
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[ee1a413] | 51 | <screen arch="ml_32,ml_x32,ml_all"><userinput>cat > ~/.bashrc << "EOF"
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[8eb3fe4] | 52 | <literal>set +h
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| 53 | umask 022
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| 54 | LFS=/mnt/lfs
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| 55 | LC_ALL=POSIX
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| 56 | LFS_TGT=x86_64-lfs-linux-gnu
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| 57 | LFS_TGT32=i686-lfs-linux-gnu
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| 58 | LFS_TGTX32=x86_64-lfs-linux-gnux32
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[37e35d2] | 59 | PATH=/usr/bin
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| 60 | if [ ! -L /bin ]; then PATH=/bin:$PATH; fi
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| 61 | PATH=$LFS/tools/bin:$PATH
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[8eb3fe4] | 62 | export LFS LC_ALL LFS_TGT LFS_TGT32 LFS_TGTX32 PATH</literal>
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[1fa2099] | 63 | EOF</userinput></screen>
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| 64 |
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[88ec930] | 65 | <variablelist>
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[37e35d2] | 66 | <title>The meaning of the settings in <filename>.bashrc</filename></title>
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[88ec930] | 67 |
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| 68 | <varlistentry>
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| 69 | <term><parameter>set +h</parameter></term>
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| 70 | <listitem>
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[1fa2099] | 71 | <para>The <command>set +h</command> command turns off
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| 72 | <command>bash</command>'s hash function. Hashing is ordinarily a useful
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| 73 | feature—<command>bash</command> uses a hash table to remember the
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| 74 | full path of executable files to avoid searching the <envar>PATH</envar>
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| 75 | time and again to find the same executable. However, the new tools should
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| 76 | be used as soon as they are installed. By switching off the hash function,
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| 77 | the shell will always search the <envar>PATH</envar> when a program is to
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| 78 | be run. As such, the shell will find the newly compiled tools in
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| 79 | <filename class="directory">$LFS/tools</filename> as soon as they are
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| 80 | available without remembering a previous version of the same program in a
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| 81 | different location.</para>
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[88ec930] | 82 | </listitem>
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| 83 | </varlistentry>
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[1fa2099] | 84 |
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[88ec930] | 85 | <varlistentry>
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| 86 | <term><parameter>umask 022</parameter></term>
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| 87 | <listitem>
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[1fa2099] | 88 | <para>Setting the user file-creation mask (umask) to 022 ensures that newly
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| 89 | created files and directories are only writable by their owner, but are
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| 90 | readable and executable by anyone (assuming default modes are used by the
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| 91 | <function>open(2)</function> system call, new files will end up with permission
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| 92 | mode 644 and directories with mode 755).</para>
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[88ec930] | 93 | </listitem>
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| 94 | </varlistentry>
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[1fa2099] | 95 |
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[88ec930] | 96 | <varlistentry>
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| 97 | <term><parameter>LFS=/mnt/lfs</parameter></term>
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| 98 | <listitem>
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[1fa2099] | 99 | <para>The <envar>LFS</envar> variable should be set to the chosen mount
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| 100 | point.</para>
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[88ec930] | 101 | </listitem>
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| 102 | </varlistentry>
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[1fa2099] | 103 |
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[88ec930] | 104 | <varlistentry>
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| 105 | <term><parameter>LC_ALL=POSIX</parameter></term>
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| 106 | <listitem>
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[1fa2099] | 107 | <para>The <envar>LC_ALL</envar> variable controls the localization of certain
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| 108 | programs, making their messages follow the conventions of a specified country.
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| 109 | Setting <envar>LC_ALL</envar> to <quote>POSIX</quote> or <quote>C</quote>
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| 110 | (the two are equivalent) ensures that everything will work as expected in
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| 111 | the chroot environment.</para>
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[88ec930] | 112 | </listitem>
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| 113 | </varlistentry>
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[1fa2099] | 114 |
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[88ec930] | 115 | <varlistentry>
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| 116 | <term><parameter>LFS_TGT=(uname -m)-lfs-linux-gnu</parameter></term>
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| 117 | <listitem>
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[1fa2099] | 118 | <para>The <envar>LFS_TGT</envar> variable sets a non-default, but compatible machine
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| 119 | description for use when building our cross compiler and linker and when cross
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| 120 | compiling our temporary toolchain. More information is contained in
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| 121 | <xref linkend="ch-tools-toolchaintechnotes" role=""/>.</para>
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[88ec930] | 122 | </listitem>
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| 123 | </varlistentry>
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[1fa2099] | 124 |
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[88ec930] | 125 | <varlistentry>
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[37e35d2] | 126 | <term><parameter>PATH=/usr/bin</parameter></term>
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[88ec930] | 127 | <listitem>
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[37e35d2] | 128 | <para>Many modern linux distributions have merged <filename
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| 129 | class="directory">/bin</filename> and <filename
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| 130 | class="directory">/usr/bin</filename>. When this is the case, the standard
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| 131 | <envar>PATH</envar> variable needs just to be set to <filename
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| 132 | class="directory">/usr/bin/</filename> for the <xref
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| 133 | linkend="chapter-temporary-tools"/> environment. When this is not the
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| 134 | case, the following line adds <filename class="directory">/bin</filename>
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| 135 | to the path.</para>
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| 136 | </listitem>
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| 137 | </varlistentry>
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| 138 |
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| 139 | <varlistentry>
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| 140 | <term><parameter>if [ ! -L /bin ]; then PATH=/bin:$PATH; fi</parameter></term>
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| 141 | <listitem>
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| 142 | <para>If <filename class="directory">/bin</filename> is not a symbolic
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| 143 | link, then it has to be added to the <envar>PATH</envar> variable.</para>
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| 144 | </listitem>
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| 145 | </varlistentry>
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| 146 |
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| 147 | <varlistentry>
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| 148 | <term><parameter>PATH=$LFS/tools/bin:$PATH</parameter></term>
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| 149 | <listitem>
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| 150 | <para>By putting <filename class="directory">$LFS/tools/bin</filename> ahead of the
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| 151 | standard <envar>PATH</envar>, the cross-compiler installed at the beginning
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| 152 | of <xref linkend="chapter-cross-tools"/> is picked up by the shell
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| 153 | immediately after its installation. This, combined with turning off hashing,
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| 154 | limits the risk that the compiler from the host be used instead of the
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| 155 | cross-compiler.</para>
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[88ec930] | 156 | </listitem>
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| 157 | </varlistentry>
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| 158 |
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| 159 | <varlistentry>
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| 160 | <term><parameter>export LFS LC_ALL LFS_TGT PATH</parameter></term>
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| 161 | <listitem>
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| 162 | <para>While the above commands have set some variables, in order
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[37e35d2] | 163 | to make them visible within any sub-shells, we export them.</para>
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[88ec930] | 164 | </listitem>
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| 165 | </varlistentry>
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| 166 |
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| 167 | </variablelist>
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[1fa2099] | 168 |
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[37e35d2] | 169 | <important>
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| 170 |
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| 171 | <para>Several commercial distributions add a non-documented instantiation
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| 172 | of <filename>/etc/bash.bashrc</filename> to the initialization of
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| 173 | <command>bash</command>. This file has the potential to modify the
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| 174 | <systemitem class="username">lfs</systemitem>
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| 175 | user's environment in ways that can affect the building of critical LFS
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| 176 | packages. To make sure the <systemitem class="username">lfs</systemitem>
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[a1ad522] | 177 | user's environment is clean, check for the
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[37e35d2] | 178 | presence of <filename>/etc/bash.bashrc</filename> and, if present, move it
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| 179 | out of the way. As the <systemitem class="username">root</systemitem>
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| 180 | user, run:</para>
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| 181 |
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| 182 | <screen role="nodump"><userinput>[ ! -e /etc/bash.bashrc ] || mv -v /etc/bash.bashrc /etc/bash.bashrc.NOUSE</userinput></screen>
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| 183 |
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| 184 | <para>After use of the <systemitem class="username">lfs</systemitem>
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| 185 | user is finished at the beginning of <xref
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| 186 | linkend="chapter-chroot-temporary-tools"/>, you can restore
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| 187 | <filename>/etc/bash.bashrc</filename> (if desired).</para>
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| 188 |
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| 189 | <para>Note that the LFS Bash package we will build in
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| 190 | <xref linkend="ch-system-bash"/> is not configured to load or execute
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| 191 | <filename>/etc/bash.bashrc</filename>, so this file is useless on a
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| 192 | completed LFS system.</para>
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| 193 | </important>
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| 194 |
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[1fa2099] | 195 | <para>Finally, to have the environment fully prepared for building the
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| 196 | temporary tools, source the just-created user profile:</para>
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| 197 |
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| 198 | <screen><userinput>source ~/.bash_profile</userinput></screen>
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| 199 |
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| 200 | </sect1>
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