source: BOOK/chroot/common/kernfs.xml@ 815d1d7

<?xml version="1.0" encoding="ISO-8859-1"?>
<!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">
  %general-entities;
]>

<sect1 id="ch-chroot-kernfs">
  <?dbhtml filename="kernfs.html"?>

  <title>Mounting Virtual Kernel File Systems</title>

    <note os="a">
      <para>The commands in the remainder of the book should be run as
      the <systemitem class="username">root</systemitem> user. Check
      that ${CLFS} is set in the
      <systemitem class="username">root</systemitem> user&rsquo;s environment
       before proceeding.</para>
    </note>

  <para>Various file systems exported by the kernel are used to communicate
  to and from the kernel itself. These file systems are virtual in that no
  disk space is used for them. The content of the file systems resides in
  memory.</para>

  <para>Begin by creating directories onto which the file systems will
  be mounted:</para>

<screen><userinput>mkdir -pv ${CLFS}/{dev,proc,run,sys}</userinput></screen>

  <para>Two device nodes, <filename class="devicefile">/dev/console</filename>
  and <filename class="devicefile">/dev/null</filename>, are required to be
  present on the file system. These are needed by the kernel even before
  starting Udev early in the boot process, so we create them here:</para>

<screen><userinput>mknod -m 600 ${CLFS}/dev/console c 5 1
mknod -m 666 ${CLFS}/dev/null c 1 3</userinput></screen>

  <para>Once the system is complete and booting, the rest of our device
  nodes will be created by the kernel's
  <systemitem class="filesystem">devtmpfs</systemitem> file system. For now
  though, we will just use the <quote>bind</quote> option in the mount command
  to make our host system's <filename class="directory">/dev</filename> structure appear in the new CLFS file system:</para>

<screen><userinput>mount -v -o bind /dev ${CLFS}/dev</userinput></screen>

  <para>Now mount the remaining file systems:</para>

<screen><userinput>mount -vt devpts -o gid=&gid-tty;,mode=620 devpts ${CLFS}/dev/pts
mount -vt proc proc ${CLFS}/proc
mount -vt tmpfs tmpfs ${CLFS}/run
mount -vt sysfs sysfs ${CLFS}/sys</userinput></screen>

  <para>On some host systems, <filename class="directory">/dev/shm</filename>
  is a symbolic link to <filename class="directory">/run/shm</filename>.
  If it is, create a directory in <filename class="directory">/run</filename>:</para>

<screen><userinput>[ -h ${CLFS}/dev/shm ] &amp;&amp; mkdir -pv ${CLFS}/$(readlink ${CLFS}/dev/shm)</userinput></screen>

  <para>Remember that if for any reason you stop working on the CLFS system
  and start again later, it is important to check that these file systems
  are mounted again before entering the chroot environment.</para>

</sect1>