lfs-book-zh_CN/chapter06/chroot.xml

<sect1 id="ch06-chroot">
<title>Entering the chroot environment</title>
<?dbhtml filename="chroot.html" dir="chapter06"?>

<para>It is time to enter the chroot environment in order to begin installing
the packages we need. Before you can chroot, however, you need to become
<emphasis>root</emphasis>, since only <emphasis>root</emphasis>
can execute the <userinput>chroot</userinput> command.</para>

<para>Just like earlier, ensure the LFS environment variable is set up properly
(if you decided to make use of it) by running <userinput>echo $LFS</userinput>
and ensuring it shows the path to your LFS partition's mount point, which is
<filename class="directory">/mnt/lfs</filename> if you followed our
example.</para>

<para>Become <emphasis>root</emphasis> and run the following command
to enter the chroot environment:</para>

<para><screen><userinput>chroot $LFS /tools/bin/env -i \
&nbsp;&nbsp;&nbsp;&nbsp;HOME=/root TERM=$TERM PS1='\u:\w\$ ' \
&nbsp;&nbsp;&nbsp;&nbsp;PATH=/bin:/usr/bin:/sbin:/usr/sbin:/tools/bin \
&nbsp;&nbsp;&nbsp;&nbsp;/tools/bin/bash --login</userinput></screen>
</para>

<para><screen><userinput>set +h</userinput></screen></para>

<para>The <userinput>-i</userinput> option given to the
<userinput>env</userinput> command will clear all variables of the chroot
environment. After that, only the HOME, TERM, PS1 and PATH variables are
set again. The TERM=$TERM construct will set the TERM variable inside chroot
to the same value as outside chroot; this variable is needed for programs
like vim and less to operate properly. If you need other variables present,
such as CFLAGS or CXXFLAGS, this is a good place to set them again.</para>

<para>Also note the use of the set +h directive.  This tells bash to not use
its internal path hashing. Without this directive, bash will remember paths
to binaries.  Since as we go thru chapter 6, we want to use our newly compiled
binaries as soon as they are installed, we turn off this function.</para>

<para>From this point on there's no need to use the LFS variable anymore,
because everything you do will be restricted to the LFS file system -- since
what the shell thinks is <filename class="directory">/</filename> is actually
the value of <filename class="directory">$LFS</filename>, which was passed to
the chroot command.</para>

<para>You have to make sure all the commands in the rest of this chapter and
in the following chapters are run from within the chroot environment.
If you ever leave this environment for any reason (rebooting for example),
you must remember to again enter chroot and mount the proc and devpts
filesystems (discussed later) before continuing with the installations.</para>

<para>Note that the bash prompt will say "I have no name!" This is
normal, as the <filename>/etc/passwd</filename> file has not been
created yet.</para>

</sect1>