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
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>

<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>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 <userinput>vim</userinput> and <userinput>less</userinput> 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>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>Notice that <filename class="directory">/tools /bin</filename> comes
last in the PATH. This means that a temporary tool will not be used any more
as soon as its final version is installed.  Well, at least when the shell
doesn't remember the locations of executed binaries -- for this reason hashing
is switched off a bit further on.</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>