Add explanatory text for new devpts mount options

git-svn-id: http://svn.linuxfromscratch.org/LFS/trunk/BOOK@10318 4aa44e1e-78dd-0310-a6d2-fbcd4c07a689

chapter01/changelog.xml

@@ -38,6 +38,10 @@
     <listitem>
       <para>2013-08-15</para>
       <itemizedlist>
+        <listitem>
+          <para>[bryan] - Add explanation for new devpts mount
+          options</para>
+        </listitem>
         <listitem>
           <para>[bdubbs] - Update several pages to fix regression
           test failures.</para>

chapter06/kernfs.xml

@@ -72,6 +72,34 @@ mknod -m 666 $LFS/dev/null c 1 3</userinput></screen>
 mount -vt proc proc $LFS/proc
 mount -vt sysfs sysfs $LFS/sys</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>.
       Inside a chroot environment, this temporary file system needs