lfs-book/chapter06/chroot.xml

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<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
  <!ENTITY % general-entities SYSTEM "../general.ent">
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<sect1 id="ch-system-chroot">
  <?dbhtml filename="chroot.html"?>

  <title>Entering the Chroot Environment</title>

  <para>It is time to enter the chroot environment to begin building and
  installing the final LFS system. As user <systemitem
  class="username">root</systemitem>, 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>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>

  <note>
    <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), ensure that the virtual kernel filesystems are mounted as
    explained in <xref linkend="ch-system-bindmount"/> and <xref
    linkend="ch-system-kernfsmount"/> and enter chroot again before continuing
    with the installation.</para>
  </note>

</sect1>