lfs-book/chapter06/devices.xml

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<sect1 id="ch-system-devices">
<title>Populating /dev</title>
<?dbhtml filename="devices.html"?>

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

<sect2>
<title>Creating Initial Device Nodes</title>

<para>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. Create these by
running the following commands:</para>

<screen><userinput>mknod -m 600 /dev/console c 5 1
mknod -m 666 /dev/null c 1 3</userinput></screen>
</sect2>

<sect2>
<title>Mounting ramfs and Populating /dev</title>

<para>The ideal way to populate <filename
class="directory">/dev</filename> is to mount a <systemitem
class="filesystem">ramfs</systemitem> onto <filename
class="directory">/dev</filename>, like <systemitem
class="filesystem">tmpfs</systemitem>, and create the devices on there
during each bootup. Since the system has not been booted, it is
necessary to do what the bootscripts would otherwise do and populate
<filename class="directory">/dev</filename>. Begin by mounting
<filename class="directory">/dev</filename>:</para>

<screen><userinput>mount -n -t ramfs none /dev</userinput></screen>

<!-- Edit Me -->
<para>Since the Udev package will not be installed until later on in the
process, create a minimal set of device nodes used for building:</para>

<screen><userinput>mknod -m 622 /dev/console c 5 1
mknod -m 666 /dev/null c 1 3
mknod -m 666 /dev/zero c 1 5
mknod -m 666 /dev/ptmx c 5 2
mknod -m 666 /dev/tty c 5 0
mknod -m 444 /dev/random c 1 8
mknod -m 444 /dev/urandom c 1 9
chown root:tty /dev/{console,ptmx,tty}</userinput></screen>
<!-- -->

<para>There are some symlinks and directories required by LFS that are
not created by Udev, so create those here:</para>

<screen><userinput>ln -s /proc/self/fd /dev/fd
ln -s /proc/self/fd/0 /dev/stdin
ln -s /proc/self/fd/1 /dev/stdout
ln -s /proc/self/fd/2 /dev/stderr
ln -s /proc/kcore /dev/core
mkdir /dev/pts
mkdir /dev/shm</userinput></screen>

<para>Finally, mount the proper virtual (kernel) file systems on the
newly-created directories:</para>

<screen><userinput>mount -t devpts -o gid=4,mode=620 none /dev/pts
mount -t tmpfs none /dev/shm</userinput></screen>

<para>The <command>mount</command> commands executed above may result
in the following warning message:</para>

<screen><computeroutput>can't open /etc/fstab: No such file or directory.</computeroutput></screen>

<para>This file&mdash;<filename>/etc/fstab</filename>&mdash;has not
been created yet but is also not required for the file systems to be
properly mounted. As such, the warning can be safely ignored.</para>
</sect2>

</sect1>