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git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@3725 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689
81 lines
3.8 KiB
XML
81 lines
3.8 KiB
XML
<?xml version="1.0" encoding="ISO-8859-1"?>
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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.3//EN" "http://www.oasis-open.org/docbook/xml/4.3/docbookx.dtd" [
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<!ENTITY % general-entities SYSTEM "../general.ent">
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%general-entities;
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]>
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<sect1 id="ch-tools-settingenviron">
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<title>Setting up the environment</title>
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<?dbhtml filename="settingenvironment.html"?>
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<para>We're going to set up a good working environment by creating two new
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startup files for the <command>bash</command> shell. While logged in as
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user <emphasis>lfs</emphasis>, issue the following command to create a new
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<filename>.bash_profile</filename>:</para>
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<screen><userinput>cat > ~/.bash_profile << <quote>EOF<quote>
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exec env -i HOME=$HOME TERM=$TERM PS1='\u:\w\$ ' /bin/bash
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EOF</userinput></screen>
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<para>Normally, when you log on as user <emphasis>lfs</emphasis>,
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the initial shell is a <emphasis>login</emphasis> shell which reads the
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<filename>/etc/profile</filename> of your host (probably containing some
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settings of environment variables) and then <filename>.bash_profile</filename>.
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The <command>exec env -i ... /bin/bash</command> command in the latter file
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replaces the running shell with a new one with a completely empty environment,
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except for the HOME, TERM and PS1 variables. This ensures that no unwanted and
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potentially hazardous environment variables from the host system leak into our
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build environment. The technique used here is a little strange, but it achieves
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the goal of enforcing a clean environment.</para>
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<para>The new instance of the shell is a <emphasis>non-login</emphasis> shell,
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which doesn't read the <filename>/etc/profile</filename> or
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<filename>.bash_profile</filename> files, but reads the
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<filename>.bashrc</filename> file instead. Create this latter file now:</para>
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<screen><userinput>cat > ~/.bashrc << <quote>EOF<quote>
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set +h
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umask 022
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LFS=/mnt/lfs
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LC_ALL=POSIX
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PATH=/tools/bin:/bin:/usr/bin
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export LFS LC_ALL PATH
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EOF</userinput></screen>
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<para>The <command>set +h</command> command turns off
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<command>bash</command>'s hash function. Normally hashing is a useful
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feature: <command>bash</command> uses a hash table to remember the
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full pathnames of executable files to avoid searching the PATH time and time
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again to find the same executable. However, we'd like the new tools to be
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used as soon as they are installed. By switching off the hash function, our
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<quote>interactive</quote> commands (<command>make</command>,
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<command>patch</command>, <command>sed</command>,
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<command>cp</command> and so forth) will always use
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the newest available version during the build process.</para>
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<para>Setting the user file-creation mask to 022 ensures that newly created
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files and directories are only writable for their owner, but readable and
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executable for anyone.</para>
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<para>The LFS variable should of course be set to the mount point you
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chose.</para>
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<para>The LC_ALL variable controls the localization of certain programs,
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making their messages follow the conventions of a specified country. If your
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host system uses a version of Glibc older than 2.2.4,
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having LC_ALL set to something other than <quote>POSIX</quote> or
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<quote>C</quote> during this chapter may cause trouble if you exit the chroot
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environment and wish to return later. By setting LC_ALL to <quote>POSIX</quote>
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(or <quote>C</quote>, the two are equivalent) we ensure that
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everything will work as expected in the chroot environment.</para>
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<para>We prepend <filename class="directory">/tools/bin</filename> to the standard PATH so
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that, as we move along through this chapter, the tools we build will get used
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during the rest of the building process.</para>
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<para>Finally, to have our environment fully prepared for building the
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temporary tools, source the just-created profile:</para>
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<screen><userinput>source ~/.bash_profile</userinput></screen>
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</sect1>
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