source: BOOK/final-preps/settingenviron.xml @ c9686cb

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Last change on this file since c9686cb was a266616, checked in by Jim Gifford <clfs@…>, 17 years ago

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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
3  "http://www.oasis-open.org/docbook/xml/4.4/docbookx.dtd" [
4  <!ENTITY % general-entities SYSTEM "../general.ent">
5  %general-entities;
6]>
7
8<sect1 id="ch-final-preps-settingenviron">
9  <?dbhtml filename="settingenvironment.html"?>
10
11  <title>Setting Up the Environment</title>
12
13  <para os="a">Set up a good working environment by creating two new startup
14  files for the <command>bash</command> shell. While logged in as user
15  <systemitem class="username">clfs</systemitem>, issue the following
16  command to create a new <filename>.bash_profile</filename>:</para>
17
18<screen os="b"><userinput>cat &gt; ~/.bash_profile &lt;&lt; "EOF"
19<literal>exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash</literal>
20EOF</userinput></screen>
21
22  <para os="c">When logged on as user <systemitem class="username">clfs</systemitem>,
23  the initial shell is usually a <emphasis>login</emphasis> shell which
24  reads the <filename>/etc/profile</filename> of the host (probably
25  containing some settings and environment variables) and then
26  <filename>.bash_profile</filename>. The
27  <command>exec env -i.../bin/bash</command> command in the
28  <filename>.bash_profile</filename> file replaces the running shell with
29  a new one with a completely empty environment, except for the
30  <envar>HOME</envar>, <envar>TERM</envar>, and <envar>PS1</envar> variables.
31  This ensures that no unwanted and potentially hazardous environment
32  variables from the host system leak into the build environment. The
33  technique used here achieves the goal of ensuring a clean environment.</para>
34
35  <para os="d">The new instance of the shell is a <emphasis>non-login</emphasis>
36  shell, which does not read the <filename>/etc/profile</filename> or
37  <filename>.bash_profile</filename> files, but rather reads the
38  <filename>.bashrc</filename> file instead. Create the
39  <filename>.bashrc</filename> file now:</para>
40
41<screen os="e"><userinput>cat &gt; ~/.bashrc &lt;&lt; "EOF"
42<literal>set +h
43umask 022
44CLFS=/mnt/clfs
45LC_ALL=POSIX
46PATH=/cross-tools/bin:/bin:/usr/bin
47export CLFS LC_ALL PATH</literal>
48EOF</userinput></screen>
49
50  <para os="f">The <command>set +h</command> command turns off
51  <command>bash</command>'s hash function. Hashing is ordinarily a useful
52  feature&mdash;<command>bash</command> uses a hash table to remember the
53  full path of executable files to avoid searching the <envar>PATH</envar>
54  time and again to find the same executable. However, the new tools should
55  be used as soon as they are installed. By switching off the hash function,
56  the shell will always search the <envar>PATH</envar> when a program is to
57  be run. As such, the shell will find the newly compiled tools in
58  <filename class="directory">$CLFS/cross-tools</filename> as soon as they are
59  available without remembering a previous version of the same program in a
60  different location.</para>
61
62  <para os="g">Setting the user file-creation mask (umask) to 022 ensures that
63  newly created files and directories are only writable by their owner,
64  but are readable and executable by anyone (assuming default modes are
65  used by the open(2) system call, new files will end up with permission
66  mode 644 and directories with mode 755).</para>
67
68  <para os="h">The <envar>CLFS</envar> variable should be set to the
69  chosen mount point.</para>
70
71  <para os="i">The <envar>LC_ALL</envar> variable controls the localization
72  of certain programs, making their messages follow the conventions of a
73  specified country.  If the host system uses a version of Glibc older
74  than 2.2.4, having <envar>LC_ALL</envar> set to something other than
75  <quote>POSIX</quote> or <quote>C</quote> (during this chapter) may cause
76  issues if you exit the chroot environment and wish to return later.
77  Setting <envar>LC_ALL</envar> to <quote>POSIX</quote> or <quote>C</quote>
78  (the two are equivalent) ensures that everything will work as expected in
79  the chroot environment.</para>
80
81  <para os="j">By putting <filename class="directory">/cross-tools/bin</filename>
82  at the beginning of the <envar>PATH</envar>, the cross-compiler
83  built in <xref linkend="chapter-cross-tools"/> will be picked up by
84  the build process for the temp-system packages before anything that
85  may be installed on the host. This, combined with turning off
86  hashing, helps to ensure that you will be using the cross-compile
87  tools to build the temp-system in /tools.</para>
88
89  <para os="k">Finally, to have the environment fully prepared for building the
90  temporary tools, source the just-created user profile:</para>
91
92<screen os="l"><userinput>source ~/.bash_profile</userinput></screen>
93
94</sect1>
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