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-tools-kernfs">
|
---|
9 | <?dbhtml filename="kernfs.html"?>
|
---|
10 |
|
---|
11 | <title>Preparing Virtual Kernel File Systems</title>
|
---|
12 |
|
---|
13 | <indexterm zone="ch-tools-kernfs">
|
---|
14 | <primary sortas="e-/dev/">/dev/*</primary>
|
---|
15 | </indexterm>
|
---|
16 |
|
---|
17 | <para>Various file systems exported by the kernel are used to communicate to
|
---|
18 | and from the kernel itself. These file systems are virtual in that no disk
|
---|
19 | space is used for them. The content of the file systems resides in
|
---|
20 | memory.</para>
|
---|
21 |
|
---|
22 | <para>Begin by creating directories onto which the file systems will be
|
---|
23 | mounted:</para>
|
---|
24 |
|
---|
25 | <screen><userinput>mkdir -pv $LFS/{dev,proc,sys,run}</userinput></screen>
|
---|
26 |
|
---|
27 | <sect2>
|
---|
28 | <title>Creating Initial Device Nodes</title>
|
---|
29 |
|
---|
30 | <para>When the kernel boots the system, it requires the presence of a few
|
---|
31 | device nodes, in particular the <filename
|
---|
32 | class="devicefile">console</filename> and <filename
|
---|
33 | class="devicefile">null</filename> devices. The device nodes must be
|
---|
34 | created on the hard disk so that they are available before the kernel
|
---|
35 | populates <systemitem class="filesystem">/dev</systemitem>), and
|
---|
36 | additionally when Linux is started with
|
---|
37 | <parameter>init=/bin/bash</parameter>. Create the devices by running the
|
---|
38 | following commands:</para>
|
---|
39 |
|
---|
40 | <screen><userinput>mknod -m 600 $LFS/dev/console c 5 1
|
---|
41 | mknod -m 666 $LFS/dev/null c 1 3</userinput></screen>
|
---|
42 |
|
---|
43 | </sect2>
|
---|
44 |
|
---|
45 | <sect2 id="ch-tools-bindmount">
|
---|
46 | <title>Mounting and Populating /dev</title>
|
---|
47 |
|
---|
48 | <para>The recommended method of populating the <filename
|
---|
49 | class="directory">/dev</filename> directory with devices is to mount a
|
---|
50 | virtual filesystem (such as <systemitem
|
---|
51 | class="filesystem">tmpfs</systemitem>) on the <filename
|
---|
52 | class="directory">/dev</filename> directory, and allow the devices to be
|
---|
53 | created dynamically on that virtual filesystem as they are detected or
|
---|
54 | accessed. Device creation is generally done during the boot process
|
---|
55 | by Udev. Since this new system does not yet have Udev and has not yet
|
---|
56 | been booted, it is necessary to mount and populate <filename
|
---|
57 | class="directory">/dev</filename> manually. This is accomplished by bind
|
---|
58 | mounting the host system's <filename class="directory">/dev</filename>
|
---|
59 | directory. A bind mount is a special type of mount that allows you to
|
---|
60 | create a mirror of a directory or mount point to some other location. Use
|
---|
61 | the following command to achieve this:</para>
|
---|
62 |
|
---|
63 | <screen><userinput>mount -v --bind /dev $LFS/dev</userinput></screen>
|
---|
64 |
|
---|
65 | </sect2>
|
---|
66 |
|
---|
67 | <sect2 id="ch-tools-kernfsmount">
|
---|
68 | <title>Mounting Virtual Kernel File Systems</title>
|
---|
69 |
|
---|
70 | <para>Now mount the remaining virtual kernel filesystems:</para>
|
---|
71 |
|
---|
72 | <screen><userinput>mount -v --bind /dev/pts $LFS/dev/pts
|
---|
73 | mount -vt proc proc $LFS/proc
|
---|
74 | mount -vt sysfs sysfs $LFS/sys
|
---|
75 | mount -vt tmpfs tmpfs $LFS/run</userinput></screen>
|
---|
76 | <!--
|
---|
77 | <variablelist>
|
---|
78 | <title>The meaning of the mount options for devpts:</title>
|
---|
79 |
|
---|
80 | <varlistentry>
|
---|
81 | <term><parameter>gid=5</parameter></term>
|
---|
82 | <listitem>
|
---|
83 | <para>This ensures that all devpts-created device nodes are owned by
|
---|
84 | group ID 5. This is the ID we will use later on for the <systemitem
|
---|
85 | class="groupname">tty</systemitem> group. We use the group ID instead
|
---|
86 | of a name, since the host system might use a different ID for its
|
---|
87 | <systemitem class="groupname">tty</systemitem> group.</para>
|
---|
88 | </listitem>
|
---|
89 | </varlistentry>
|
---|
90 |
|
---|
91 | <varlistentry>
|
---|
92 | <term><parameter>mode=0620</parameter></term>
|
---|
93 | <listitem>
|
---|
94 | <para>This ensures that all devpts-created device nodes have mode 0620
|
---|
95 | (user readable and writable, group writable). Together with the
|
---|
96 | option above, this ensures that devpts will create device nodes that
|
---|
97 | meet the requirements of grantpt(), meaning the Glibc
|
---|
98 | <command>pt_chown</command> helper binary (which is not installed by
|
---|
99 | default) is not necessary.</para>
|
---|
100 | </listitem>
|
---|
101 | </varlistentry>
|
---|
102 |
|
---|
103 | </variablelist>
|
---|
104 | -->
|
---|
105 | <para>In some host systems, <filename>/dev/shm</filename> is a
|
---|
106 | symbolic link to <filename class="directory">/run/shm</filename>.
|
---|
107 | The /run tmpfs was mounted above so in this case only a
|
---|
108 | directory needs to be created.</para>
|
---|
109 |
|
---|
110 | <screen><userinput>if [ -h $LFS/dev/shm ]; then
|
---|
111 | mkdir -pv $LFS/$(readlink $LFS/dev/shm)
|
---|
112 | fi</userinput></screen>
|
---|
113 |
|
---|
114 | </sect2>
|
---|
115 |
|
---|
116 | </sect1>
|
---|