lfs-book/chapter06/mountproc.xml

<sect1 id="ch-system-proc">
<title>Mounting the proc and devpts file systems</title>
<?dbhtml filename="proc.html" dir="chapter06"?>

<para>In order for certain programs to function properly, the
<emphasis>proc</emphasis> and <emphasis>devpts</emphasis> file systems must be
available within the chroot environment. Since kernel version 2.4 a file system
can be mounted as many times and in as many places as you like, thus it's not a
problem that these file systems are already mounted on your host system,
especially so because they are virtual file systems.</para>

<para>First make the mount points for these filesystems:</para>

<screen><userinput>mkdir -p $LFS/{proc,dev/pts}</userinput></screen>

<para>Now become <emphasis>root</emphasis>, since only
<emphasis>root</emphasis> can mount file systems in unusual places. Then
check again that the LFS environment variable is set correctly by running 
<userinput>echo $LFS</userinput> and making sure it shows the path to your LFS
partition's mount point, which is <filename
class="directory">/mnt/lfs</filename> if you followed our example.</para>

<para>The <emphasis>proc</emphasis> file system is the process information
pseudo file system through which the kernel provides information about the
status of the system. Mount it with:</para>

<screen><userinput>mount proc $LFS/proc -t proc</userinput></screen>

<para>The <emphasis>devpts</emphasis> file system is now the most common way
for pseudo terminals (PTYs) to be implemented. Mount it with:</para>

<screen><userinput>mount devpts $LFS/dev/pts -t devpts</userinput></screen>

<para>This last command might fail with an error to the effect of:</para>

<blockquote><screen>filesystem devpts not supported by kernel</screen></blockquote>

<para>The most likely cause for this is that your host system's kernel was
compiled without support for the devpts file system. You can check which file
systems your kernel supports by peeking into its internals with
<command>cat /proc/filesystems</command>. If a file system type named
<emphasis>devfs</emphasis> is listed there, then we'll be able to work around
the problem by mounting the host's devfs file system on top of the new
<filename>/dev</filename> structure which we'll create later on in the section
on <xref linkend="ch-system-MAKEDEV"/>. If devfs was not listed, do not worry
because there is yet a third way to get PTYs working inside the chroot
environment. We'll cover this shortly in the aforementioned
<xref linkend="ch-system-MAKEDEV"/> section.</para>

<para>Remember, if for any reason you stop working on your LFS, and start again
later, it's important to check that these file systems are mounted again before
entering the chroot environment, otherwise some problems could occur.</para>

</sect1>