[519ee45] | 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-tools-settingenviron">
|
---|
| 9 | <?dbhtml filename="settingenvironment.html"?>
|
---|
| 10 |
|
---|
| 11 | <title>Setting Up the Environment</title>
|
---|
| 12 |
|
---|
| 13 | <para>Set up a good working environment by creating two new startup files
|
---|
| 14 | for the <command>bash</command> shell. While logged in as user
|
---|
| 15 | <systemitem class="username">lfs</systemitem>, issue the following command
|
---|
| 16 | to create a new <filename>.bash_profile</filename>:</para>
|
---|
| 17 |
|
---|
| 18 | <screen><userinput>cat > ~/.bash_profile << "EOF"
|
---|
| 19 | <literal>exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash</literal>
|
---|
| 20 | EOF</userinput></screen>
|
---|
| 21 |
|
---|
| 22 | <para>When logged on as user <systemitem class="username">lfs</systemitem>,
|
---|
| 23 | the initial shell is usually a <emphasis>login</emphasis> shell which reads
|
---|
| 24 | the <filename>/etc/profile</filename> of the host (probably containing some
|
---|
| 25 | settings and environment variables) and then <filename>.bash_profile</filename>.
|
---|
| 26 | The <command>exec env -i.../bin/bash</command> command in the
|
---|
| 27 | <filename>.bash_profile</filename> file replaces the running shell with a new
|
---|
| 28 | one with a completely empty environment, except for the <envar>HOME</envar>,
|
---|
| 29 | <envar>TERM</envar>, and <envar>PS1</envar> variables. This ensures that no
|
---|
| 30 | unwanted and potentially hazardous environment variables from the host system
|
---|
| 31 | leak into the build environment. The technique used here achieves the goal of
|
---|
| 32 | ensuring a clean environment.</para>
|
---|
| 33 |
|
---|
| 34 | <para>The new instance of the shell is a <emphasis>non-login</emphasis>
|
---|
| 35 | shell, which does not read the <filename>/etc/profile</filename> or
|
---|
| 36 | <filename>.bash_profile</filename> files, but rather reads the
|
---|
| 37 | <filename>.bashrc</filename> file instead. Create the
|
---|
| 38 | <filename>.bashrc</filename> file now:</para>
|
---|
| 39 |
|
---|
| 40 | <screen><userinput>cat > ~/.bashrc << "EOF"
|
---|
| 41 | <literal>set +h
|
---|
| 42 | umask 022
|
---|
| 43 | LFS=/mnt/lfs
|
---|
| 44 | LC_ALL=POSIX
|
---|
| 45 | PATH=/tools/bin:/bin:/usr/bin
|
---|
| 46 | export LFS LC_ALL PATH</literal>
|
---|
| 47 | EOF</userinput></screen>
|
---|
| 48 |
|
---|
| 49 | <para>The <command>set +h</command> command turns off
|
---|
| 50 | <command>bash</command>'s hash function. Hashing is ordinarily a useful
|
---|
| 51 | feature—<command>bash</command> uses a hash table to remember the
|
---|
| 52 | full path of executable files to avoid searching the <envar>PATH</envar>
|
---|
| 53 | time and again to find the same executable. However, the new tools should
|
---|
| 54 | be used as soon as they are installed. By switching off the hash function,
|
---|
| 55 | the shell will always search the <envar>PATH</envar> when a program is to
|
---|
| 56 | be run. As such, the shell will find the newly compiled tools in
|
---|
| 57 | <filename class="directory">$LFS/tools</filename> as soon as they are
|
---|
| 58 | available without remembering a previous version of the same program in a
|
---|
| 59 | different location.</para>
|
---|
| 60 |
|
---|
| 61 | <para>Setting the user file-creation mask (umask) to 022 ensures that newly
|
---|
| 62 | created files and directories are only writable by their owner, but are
|
---|
| 63 | readable and executable by anyone (assuming default modes are used by the
|
---|
| 64 | <function>open(2)</function> system call, new files will end up with permission
|
---|
| 65 | mode 644 and directories with mode 755).</para>
|
---|
| 66 |
|
---|
| 67 | <para>The <envar>LFS</envar> variable should be set to the chosen mount
|
---|
| 68 | point.</para>
|
---|
| 69 |
|
---|
| 70 | <para>The <envar>LC_ALL</envar> variable controls the localization of certain
|
---|
| 71 | programs, making their messages follow the conventions of a specified country.
|
---|
| 72 | If the host system uses a version of Glibc older than 2.2.4, having
|
---|
| 73 | <envar>LC_ALL</envar> set to something other than <quote>POSIX</quote> or
|
---|
| 74 | <quote>C</quote> (during this chapter) may cause issues if you exit the chroot
|
---|
| 75 | environment and wish to return later. Setting <envar>LC_ALL</envar> to
|
---|
| 76 | <quote>POSIX</quote> or <quote>C</quote> (the two are equivalent) ensures that
|
---|
| 77 | everything will work as expected in the chroot environment.</para>
|
---|
| 78 |
|
---|
| 79 | <para>By putting <filename class="directory">/tools/bin</filename> ahead of the
|
---|
| 80 | standard <envar>PATH</envar>, all the programs installed in <xref
|
---|
| 81 | linkend="chapter-temporary-tools"/> are picked up by the shell immediately after
|
---|
| 82 | their installation. This, combined with turning off hashing, limits the risk
|
---|
| 83 | that old programs are used from the host when the same programs are available in
|
---|
| 84 | the chapter 5 environment.</para>
|
---|
| 85 |
|
---|
| 86 | <para>Finally, to have the environment fully prepared for building the
|
---|
| 87 | temporary tools, source the just-created user profile:</para>
|
---|
| 88 |
|
---|
| 89 | <screen><userinput>source ~/.bash_profile</userinput></screen>
|
---|
| 90 |
|
---|
| 91 | </sect1>
|
---|