source: BOOK/chroot/common/kernfs.xml

systemd
Last change on this file was 799de33, checked in by Chris Staub <chris@…>, 7 years ago

Updated file system mount commands for chroot

  • Property mode set to 100644
File size: 2.8 KB
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1<?xml version="1.0" encoding="ISO-8859-1"?>
2<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
3  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
4  <!ENTITY % general-entities SYSTEM "../../general.ent">
5  %general-entities;
6]>
7
8<sect1 id="ch-chroot-kernfs">
9  <?dbhtml filename="kernfs.html"?>
10
11  <title>Mounting Virtual Kernel File Systems</title>
12
13    <note os="a">
14      <para>The commands in the remainder of the book should be run as
15      the <systemitem class="username">root</systemitem> user. Check
16      that ${CLFS} is set in the
17      <systemitem class="username">root</systemitem> user&rsquo;s environment
18       before proceeding.</para>
19    </note>
20
21  <para>Various file systems exported by the kernel are used to communicate
22  to and from the kernel itself. These file systems are virtual in that no
23  disk space is used for them. The content of the file systems resides in
24  memory.</para>
25
26  <para>Begin by creating directories onto which the file systems will
27  be mounted:</para>
28
29<screen><userinput>mkdir -pv ${CLFS}/{dev,proc,run,sys}</userinput></screen>
30
31  <para>Two device nodes, <filename class="devicefile">/dev/console</filename>
32  and <filename class="devicefile">/dev/null</filename>, are required to be
33  present on the file system. These are needed by the kernel even before
34  starting Udev early in the boot process, so we create them here:</para>
35
36<screen><userinput>mknod -m 600 ${CLFS}/dev/console c 5 1
37mknod -m 666 ${CLFS}/dev/null c 1 3</userinput></screen>
38
39  <para>Once the system is complete and booting, the rest of our device
40  nodes will be created by the kernel's
41  <systemitem class="filesystem">devtmpfs</systemitem> file system. For now
42  though, we will just use the <quote>bind</quote> option in the mount command
43  to make our host system's <filename class="directory">/dev</filename> structure appear in the new CLFS file system:</para>
44
45<screen><userinput>mount -v -o bind /dev ${CLFS}/dev</userinput></screen>
46
47  <para>Now mount the remaining file systems:</para>
48
49<screen><userinput>mount -vt devpts -o gid=&gid-tty;,mode=620 devpts ${CLFS}/dev/pts
50mount -vt proc proc ${CLFS}/proc
51mount -vt tmpfs tmpfs ${CLFS}/run
52mount -vt sysfs sysfs ${CLFS}/sys</userinput></screen>
53
54  <para>On some host systems, <filename class="directory">/dev/shm</filename>
55  is a symbolic link to <filename class="directory">/run/shm</filename>.
56  If it is, create a directory in <filename class="directory">/run</filename>:</para>
57
58<screen><userinput>[ -h ${CLFS}/dev/shm ] &amp;&amp; mkdir -pv ${CLFS}/$(readlink ${CLFS}/dev/shm)</userinput></screen>
59
60  <para>Remember that if for any reason you stop working on the CLFS system
61  and start again later, it is important to check that these file systems
62  are mounted again before entering the chroot environment.</para>
63
64</sect1>
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