[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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[673b0d8] | 46 | PATH=/tools/bin:/bin:/usr/bin
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[4e82d47] | 47 | export LFS LC_ALL LFS_TGT PATH</literal>
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[55851d6] | 48 | EOF</userinput></screen>
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[673b0d8] | 49 |
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[df43be1] | 50 | <variablelist>
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| 51 | <title>The meaning of the command line options in <filename>.bashrc</filename></title>
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| 52 |
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| 53 | <varlistentry>
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| 54 | <term><parameter>set +h</parameter></term>
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| 55 | <listitem>
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[6a3b6af] | 56 | <para>The <command>set +h</command> command turns off
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| 57 | <command>bash</command>'s hash function. Hashing is ordinarily a useful
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| 58 | feature—<command>bash</command> uses a hash table to remember the
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| 59 | full path of executable files to avoid searching the <envar>PATH</envar>
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| 60 | time and again to find the same executable. However, the new tools should
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| 61 | be used as soon as they are installed. By switching off the hash function,
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| 62 | the shell will always search the <envar>PATH</envar> when a program is to
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| 63 | be run. As such, the shell will find the newly compiled tools in
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| 64 | <filename class="directory">$LFS/tools</filename> as soon as they are
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| 65 | available without remembering a previous version of the same program in a
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| 66 | different location.</para>
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[df43be1] | 67 | </listitem>
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| 68 | </varlistentry>
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[81fd230] | 69 |
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[df43be1] | 70 | <varlistentry>
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| 71 | <term><parameter>umask 022</parameter></term>
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| 72 | <listitem>
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[6a3b6af] | 73 | <para>Setting the user file-creation mask (umask) to 022 ensures that newly
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| 74 | created files and directories are only writable by their owner, but are
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| 75 | readable and executable by anyone (assuming default modes are used by the
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| 76 | <function>open(2)</function> system call, new files will end up with permission
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| 77 | mode 644 and directories with mode 755).</para>
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[df43be1] | 78 | </listitem>
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| 79 | </varlistentry>
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[81fd230] | 80 |
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[df43be1] | 81 | <varlistentry>
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| 82 | <term><parameter>LFS=/mnt/lfs</parameter></term>
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| 83 | <listitem>
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[6a3b6af] | 84 | <para>The <envar>LFS</envar> variable should be set to the chosen mount
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| 85 | point.</para>
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[df43be1] | 86 | </listitem>
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| 87 | </varlistentry>
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[81fd230] | 88 |
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[df43be1] | 89 | <varlistentry>
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| 90 | <term><parameter>LC_ALL=POSIX</parameter></term>
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| 91 | <listitem>
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[6a3b6af] | 92 | <para>The <envar>LC_ALL</envar> variable controls the localization of certain
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| 93 | programs, making their messages follow the conventions of a specified country.
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[448e226] | 94 | Setting <envar>LC_ALL</envar> to <quote>POSIX</quote> or <quote>C</quote>
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| 95 | (the two are equivalent) ensures that everything will work as expected in
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| 96 | the chroot environment.</para>
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[df43be1] | 97 | </listitem>
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| 98 | </varlistentry>
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[81fd230] | 99 |
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[df43be1] | 100 | <varlistentry>
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| 101 | <term><parameter>LFS_TGT=(uname -m)-lfs-linux-gnu</parameter></term>
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| 102 | <listitem>
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[4e82d47] | 103 | <para>The <envar>LFS_TGT</envar> variable sets a non-default, but compatible machine
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| 104 | description for use when building our cross compiler and linker and when cross
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| 105 | compiling our temporary toolchain. More information is contained in
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| 106 | <xref linkend="ch-tools-toolchaintechnotes" role=""/>.</para>
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[df43be1] | 107 | </listitem>
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| 108 | </varlistentry>
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[4e82d47] | 109 |
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[df43be1] | 110 | <varlistentry>
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| 111 | <term><parameter>PATH=/tools/bin:/bin:/usr/bin</parameter></term>
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| 112 | <listitem>
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[6a3b6af] | 113 | <para>By putting <filename class="directory">/tools/bin</filename> ahead of the
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| 114 | standard <envar>PATH</envar>, all the programs installed in <xref
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| 115 | linkend="chapter-temporary-tools"/> are picked up by the shell immediately after
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| 116 | their installation. This, combined with turning off hashing, limits the risk
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| 117 | that old programs are used from the host when the same programs are available in
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[df43be1] | 118 | the Chapter 5 environment.</para>
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| 119 | </listitem>
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| 120 | </varlistentry>
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| 121 |
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| 122 | <varlistentry>
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| 123 | <term><parameter>export LFS LC_ALL LFS_TGT PATH</parameter></term>
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| 124 | <listitem>
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| 125 | <para>While the above commands have set some variables, in order
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| 126 | to make them visible within any sub-shells, we export them</para>
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| 127 | </listitem>
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| 128 | </varlistentry>
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| 129 |
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| 130 | </variablelist>
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[81fd230] | 131 |
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[6a3b6af] | 132 | <para>Finally, to have the environment fully prepared for building the
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| 133 | temporary tools, source the just-created user profile:</para>
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[81fd230] | 134 |
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[673b0d8] | 135 | <screen><userinput>source ~/.bash_profile</userinput></screen>
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| 136 |
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| 137 | </sect1>
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