source: BOOK/boot/common/devices.xml @ ab628f9

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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">
  %general-entities;
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<sect1 id="ch-boot-devices">
  <?dbhtml filename="devices.html"?>

  <title>Populating /dev</title>

  <indexterm zone="ch-boot-devices">
    <primary sortas="e-/dev/*">/dev/*</primary>
  </indexterm>

  <sect2>
    <title>Creating Initial Device Nodes</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 os="b">When the kernel boots the system, it requires the presence
    of a few device nodes, in particular the <filename
    class="devicefile">console</filename> and <filename
    class="devicefile">null</filename> devices. The device nodes will
    be created on the hard disk so that they are available before
    <command>udev</command> has been started, and additionally when Linux
    is started in single user mode (hence the restrictive permissions on
    <filename class="devicefile">console</filename>). Create these by running
    the following commands:</para>

<screen><userinput>mknod -m 0600 ${CLFS}/dev/console c 5 1
mknod -m 0666 ${CLFS}/dev/null c 1 3
mknod -m 0666 ${CLFS}/dev/zero c 1 5</userinput></screen>

    <para>When systemd starts a tmpfs filesystem is mounted over
    <filename class="directory">/dev</filename> and the previous entries are
    no-longer available. The folling command creates files that are copied
    over when udevd starts:</para>

<screen><userinput>mkdir -pv ${CLFS}/lib/udev/devices/{pts,shm}
mknod -m 0600 ${CLFS}/lib/udev/devices/console c 5 1
mknod -m 0666 ${CLFS}/lib/udev/devices/null c 1 3
mknod -m 0666 ${CLFS}/lib/udev/devices/zero c 1 5
mknod -m 0600 ${CLFS}/lib/udev/devices/kmsg c 1 11
ln -snvf /proc/self/fd ${CLFS}/lib/udev/devices/fd
ln -snvf /proc/self/fd/0 ${CLFS}/lib/udev/devices/stdin
ln -snvf /proc/self/fd/1 ${CLFS}/lib/udev/devices/stdout
ln -snvf /proc/self/fd/2 ${CLFS}/lib/udev/devices/stderr
ln -snvf /proc/kcore ${CLFS}/lib/udev/devices/core</userinput></screen>

  </sect2>

</sect1>