lfs-book-zh_CN/chapter06/chroot.xml

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<sect1 id="ch-system-chroot">
<title>Entering the Chroot Environment</title>
<?dbhtml filename="chroot.html"?>

<para>It is time to enter the chroot environment to begin
building and installing the final LFS system. As user
<emphasis>root</emphasis>, run the following command to enter the
realm that is, at the moment, populated with only the temporary
tools:</para>

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

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

<para>From this point on, there is no need to use the
<envar>LFS</envar> variable anymore, because all work will be
restricted to the LFS file system.  This is because the Bash shell is
told that <filename class="directory">$LFS</filename> is now the root
(<filename class="directory">/</filename>) directory.</para>

<para>Notice that <filename class="directory">/tools/bin</filename> comes last
in the <envar>PATH</envar>. This means that a temporary tool will no longer be
used once its final version is installed. This occurs when the shell does not
<quote>remember</quote> the locations of executed binaries&mdash;for this
reason, hashing is switched off by passing the <parameter>+h</parameter> option
to <command>bash</command>.</para>

<para>It is important that all the commands throughout the remainder
of this chapter and the following chapters are run from within the
chroot environment. If you leave this environment for any reason
(rebooting for example), remember to first mount the <systemitem
class="filesystem">proc</systemitem> and <systemitem
class="filesystem">devpts</systemitem> file systems (discussed in the
previous section) and enter chroot again before continuing with the
installations.</para>

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

</sect1>