[fcc02767] | 1 | <?xml version="1.0" encoding="ISO-8859-1"?>
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| 2 | <!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
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| 3 | "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
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| 4 | <!ENTITY % general-entities SYSTEM "../general.ent">
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| 5 | %general-entities;
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| 6 | ]>
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| 7 |
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| 8 | <sect1 id="ch-tools-kernfs">
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| 9 | <?dbhtml filename="kernfs.html"?>
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| 10 |
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| 11 | <title>Preparing Virtual Kernel File Systems</title>
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| 12 |
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| 13 | <indexterm zone="ch-tools-kernfs">
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| 14 | <primary sortas="e-/dev/">/dev/*</primary>
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| 15 | </indexterm>
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| 16 |
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| 17 | <para>Various file systems exported by the kernel are used to communicate to
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| 18 | and from the kernel itself. These file systems are virtual in that no disk
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| 19 | space is used for them. The content of the file systems resides in
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| 20 | memory.</para>
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| 21 |
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| 22 | <para>Begin by creating directories onto which the file systems will be
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| 23 | mounted:</para>
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| 24 |
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| 25 | <screen><userinput>mkdir -pv $LFS/{dev,proc,sys,run}</userinput></screen>
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| 26 |
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| 27 | <sect2>
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| 28 | <title>Creating Initial Device Nodes</title>
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| 29 |
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| 30 | <para>When the kernel boots the system, it requires the presence of a few
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| 31 | device nodes, in particular the <filename
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| 32 | class="devicefile">console</filename> and <filename
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[387a32af] | 33 | class="devicefile">null</filename> devices. The device nodes must be
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| 34 | created on the hard disk so that they are available before the kernel
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| 35 | populates <systemitem class="filesystem">/dev</systemitem>), and
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| 36 | additionally when Linux is started with
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[fcc02767] | 37 | <parameter>init=/bin/bash</parameter>. Create the devices by running the
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| 38 | following commands:</para>
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| 39 |
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| 40 | <screen><userinput>mknod -m 600 $LFS/dev/console c 5 1
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| 41 | mknod -m 666 $LFS/dev/null c 1 3</userinput></screen>
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| 42 |
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| 43 | </sect2>
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| 44 |
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[bfab1b2] | 45 | <sect2 id="ch-tools-bindmount">
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[fcc02767] | 46 | <title>Mounting and Populating /dev</title>
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| 47 |
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| 48 | <para>The recommended method of populating the <filename
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| 49 | class="directory">/dev</filename> directory with devices is to mount a
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| 50 | virtual filesystem (such as <systemitem
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| 51 | class="filesystem">tmpfs</systemitem>) on the <filename
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| 52 | class="directory">/dev</filename> directory, and allow the devices to be
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| 53 | created dynamically on that virtual filesystem as they are detected or
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| 54 | accessed. Device creation is generally done during the boot process
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| 55 | by Udev. Since this new system does not yet have Udev and has not yet
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| 56 | been booted, it is necessary to mount and populate <filename
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| 57 | class="directory">/dev</filename> manually. This is accomplished by bind
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| 58 | mounting the host system's <filename class="directory">/dev</filename>
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| 59 | directory. A bind mount is a special type of mount that allows you to
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| 60 | create a mirror of a directory or mount point to some other location. Use
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| 61 | the following command to achieve this:</para>
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| 62 |
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| 63 | <screen><userinput>mount -v --bind /dev $LFS/dev</userinput></screen>
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| 64 |
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| 65 | </sect2>
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| 66 |
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[bfab1b2] | 67 | <sect2 id="ch-tools-kernfsmount">
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[fcc02767] | 68 | <title>Mounting Virtual Kernel File Systems</title>
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| 69 |
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| 70 | <para>Now mount the remaining virtual kernel filesystems:</para>
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| 71 |
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| 72 | <screen><userinput>mount -v --bind /dev/pts $LFS/dev/pts
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| 73 | mount -vt proc proc $LFS/proc
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| 74 | mount -vt sysfs sysfs $LFS/sys
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| 75 | mount -vt tmpfs tmpfs $LFS/run</userinput></screen>
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[387a32af] | 76 | <!--
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[fcc02767] | 77 | <variablelist>
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| 78 | <title>The meaning of the mount options for devpts:</title>
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| 79 |
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| 80 | <varlistentry>
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| 81 | <term><parameter>gid=5</parameter></term>
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| 82 | <listitem>
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| 83 | <para>This ensures that all devpts-created device nodes are owned by
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| 84 | group ID 5. This is the ID we will use later on for the <systemitem
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| 85 | class="groupname">tty</systemitem> group. We use the group ID instead
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| 86 | of a name, since the host system might use a different ID for its
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| 87 | <systemitem class="groupname">tty</systemitem> group.</para>
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| 88 | </listitem>
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| 89 | </varlistentry>
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| 90 |
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| 91 | <varlistentry>
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| 92 | <term><parameter>mode=0620</parameter></term>
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| 93 | <listitem>
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| 94 | <para>This ensures that all devpts-created device nodes have mode 0620
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| 95 | (user readable and writable, group writable). Together with the
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| 96 | option above, this ensures that devpts will create device nodes that
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| 97 | meet the requirements of grantpt(), meaning the Glibc
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| 98 | <command>pt_chown</command> helper binary (which is not installed by
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| 99 | default) is not necessary.</para>
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| 100 | </listitem>
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| 101 | </varlistentry>
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| 102 |
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| 103 | </variablelist>
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[387a32af] | 104 | -->
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[fcc02767] | 105 | <para>In some host systems, <filename>/dev/shm</filename> is a
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| 106 | symbolic link to <filename class="directory">/run/shm</filename>.
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[2c8fdfc] | 107 | The /run tmpfs was mounted above so in this case only a
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[fcc02767] | 108 | directory needs to be created.</para>
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| 109 |
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| 110 | <screen><userinput>if [ -h $LFS/dev/shm ]; then
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| 111 | mkdir -pv $LFS/$(readlink $LFS/dev/shm)
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| 112 | fi</userinput></screen>
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| 113 |
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| 114 | </sect2>
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| 115 |
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| 116 | </sect1>
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