Initial commit of alternative cross LFS

git-svn-id: http://svn.linuxfromscratch.org/LFS/branches/cross2@11897 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

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+<?xml version="1.0" encoding="ISO-8859-1"?>
+<!DOCTYPE sect1 PUBLIC "-//OASIS//DTD DocBook XML V4.5//EN"
+  "http://www.oasis-open.org/docbook/xml/4.5/docbookx.dtd" [
+  <!ENTITY % general-entities SYSTEM "../general.ent">
+  %general-entities;
+]>
+
+<sect1 id="ch-tools-kernfs">
+  <?dbhtml filename="kernfs.html"?>
+
+  <title>Preparing Virtual Kernel File Systems</title>
+
+  <indexterm zone="ch-tools-kernfs">
+    <primary sortas="e-/dev/">/dev/*</primary>
+  </indexterm>
+
+    <para>Various file systems exported by the kernel are used to communicate to
+    and from the kernel itself. These file systems are virtual in that no disk
+    space is used for them. The content of the file systems resides in
+    memory.</para>
+
+    <para>Begin by creating directories onto which the file systems will be
+    mounted:</para>
+
+<screen><userinput>mkdir -pv $LFS/{dev,proc,sys,run}</userinput></screen>
+
+  <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. The device nodes must be created
+    on the hard disk so that they are available before <command>udevd</command>
+    has been started, and additionally when Linux is started with
+    <parameter>init=/bin/bash</parameter>. Create the devices by running the
+    following commands:</para>
+
+<screen><userinput>mknod -m 600 $LFS/dev/console c 5 1
+mknod -m 666 $LFS/dev/null c 1 3</userinput></screen>
+
+  </sect2>
+
+  <sect2 id="ch-system-bindmount">
+    <title>Mounting and Populating /dev</title>
+
+      <para>The recommended method of populating the <filename
+      class="directory">/dev</filename> directory with devices is to mount a
+      virtual filesystem (such as <systemitem
+      class="filesystem">tmpfs</systemitem>) on the <filename
+      class="directory">/dev</filename> directory, and allow the devices to be
+      created dynamically on that virtual filesystem as they are detected or
+      accessed. Device creation is generally done during the boot process
+      by Udev. Since this new system does not yet have Udev and has not yet
+      been booted, it is necessary to mount and populate <filename
+      class="directory">/dev</filename> manually. This is accomplished by bind
+      mounting the host system's <filename class="directory">/dev</filename>
+      directory. A bind mount is a special type of mount that allows you to
+      create a mirror of a directory or mount point to some other location. Use
+      the following command to achieve this:</para>
+
+<screen><userinput>mount -v --bind /dev $LFS/dev</userinput></screen>
+
+  </sect2>
+
+  <sect2 id="ch-system-kernfsmount">
+    <title>Mounting Virtual Kernel File Systems</title>
+
+      <para>Now mount the remaining virtual kernel filesystems:</para>
+
+<screen><userinput>mount -v --bind /dev/pts $LFS/dev/pts
+mount -vt proc proc $LFS/proc
+mount -vt sysfs sysfs $LFS/sys
+mount -vt tmpfs tmpfs $LFS/run</userinput></screen>
+
+    <variablelist>
+      <title>The meaning of the mount options for devpts:</title>
+
+      <varlistentry>
+        <term><parameter>gid=5</parameter></term>
+        <listitem>
+          <para>This ensures that all devpts-created device nodes are owned by
+          group ID 5.  This is the ID we will use later on for the <systemitem
+          class="groupname">tty</systemitem> group.  We use the group ID instead
+          of a name, since the host system might use a different ID for its
+          <systemitem class="groupname">tty</systemitem> group.</para>
+        </listitem>
+      </varlistentry>
+
+      <varlistentry>
+        <term><parameter>mode=0620</parameter></term>
+        <listitem>
+          <para>This ensures that all devpts-created device nodes have mode 0620
+          (user readable and writable, group writable).  Together with the
+          option above, this ensures that devpts will create device nodes that
+          meet the requirements of grantpt(), meaning the Glibc
+          <command>pt_chown</command> helper binary (which is not installed by
+          default) is not necessary.</para>
+        </listitem>
+      </varlistentry>
+
+    </variablelist>
+
+      <para>In some host systems, <filename>/dev/shm</filename> is a
+      symbolic link to <filename class="directory">/run/shm</filename>.
+      The /run tmpfs was mounted above so in this case only a 
+      directory needs to be created.</para>
+
+<screen><userinput>if [ -h $LFS/dev/shm ]; then
+  mkdir -pv $LFS/$(readlink $LFS/dev/shm)
+fi</userinput></screen>
+
+  </sect2>
+
+</sect1>