lfs-book-zh_CN/chapter05/setting-environment.xml

<sect1 id="ch05-settingenviron">
<title>Setting up the environment</title>
<?dbhtml filename="settingenvironment.html" dir="chapter05"?>

<para>While logged in as user <emphasis>lfs</emphasis>, issue the
following commands to set up a good work environment:</para>

<screen><userinput>cat &gt; ~/.bash_profile &lt;&lt; "EOF"</userinput>
set +h
umask 022
LFS=/mnt/lfs
LC_ALL=POSIX
PATH=/tools/bin:$PATH
export LFS LC_ALL PATH
unset CC CXX CPP LD_LIBRARY_PATH LD_PRELOAD
<userinput>EOF

source ~/.bash_profile</userinput></screen>

<para>The <userinput>set +h</userinput> command turns off
<userinput>bash</userinput>'s hash function. Normally hashing is a useful
feature: <userinput>bash</userinput> uses a hash table to remember the
full pathnames of executable files to avoid searching the PATH time and time
again to find the same executable. However, we'd like the new tools to be
used as soon as they are installed.  By switching off the hash function, our
"interactive" commands (<userinput>make</userinput>,
<userinput>patch</userinput>, <userinput>sed</userinput>,
<userinput>cp</userinput> and so forth) will always use
the newest available version during the build process.</para>

<para>Setting the user file-creation mask to 022 ensures that newly created
files and directories are only writable for their owner, but readable and
executable for anyone.</para>
 
<para>The LFS variable should of course be set to the mount point you
chose.</para>

<para>The LC_ALL variable controls the localization of certain programs,
making their messages follow the conventions of a specified country. If your
host system uses a version of Glibc older than 2.2.4,
having LC_ALL set to something other than "POSIX" or "C" during this chapter
may cause trouble if you exit the chroot environment and wish to return later.
By setting LC_ALL to "POSIX" (or "C", the two are equivalent)  we ensure that
everything will work as expected in the chroot environment.</para>

<para>We prepend <filename>/tools/bin</filename> to the standard PATH so
that, as we move along through this chapter, the tools we build will get used
during the rest of the building process.</para>

<para>The CC, CXX, CPP, LD_LIBRARY_PATH and LD_PRELOAD environment variables all
have the potential to cause havoc with our Chapter 5 toolchain. We therefore
unset them to prevent any chance of this happening.</para>

<para>Now, after sourcing the just-created profile, we're all set to begin
building the temporary tools that will support us in later chapters.</para>

</sect1>