grub: add a note about filesystem UUID and partition UUID usage

Text only change.

1 files changed, 32 insertions, 0 deletions

diff --git a/chapter10/grub.xml b/chapter10/grub.xml
index c569525c9..233902633 100644
--- a/chapter10/grub.xml
+++ b/chapter10/grub.xml
@@ -155,6 +155,38 @@ EOF</userinput></screen>
     <emphasis>set root</emphasis> line to point to the boot partition.
     </para></note>
 
+    <note>
+      <para>The GRUB designator for a partition may change if you added or
+      removed some disks (including removable disks like USB thumb devices).
+      The change may cause boot failure because
+      <filename>grub.cfg</filename> refers to some <quote>old</quote>
+      designators.  If you wish to avoid such a problem, you may use
+      the UUID of partition and filesystem instead of GRUB designator to
+      specify a partition.
+      Run <command>lsblk -o UUID,PARTUUID,PATH,MOUNTPOINT</command> to show
+      the UUID of your filesystems (in <literal>UUID</literal> column) and
+      partitions (in <literal>PARTUUID</literal> column).  Then replace
+      <literal>set root=(hdx,y)</literal> with
+      <literal>search --set=root --fs-uuid <replaceable>&lt;UUID of the filesystem where the kernel is installed&gt;</replaceable></literal>, and replace
+      <literal>root=/dev/sda2</literal> with
+      <literal>root=PARTUUID=<replaceable>&lt;UUID of the partition where LFS is built&gt;</replaceable></literal>.</para>
+      <para>Note that the UUID of a partition and the UUID of the filesystem
+      in this partition is completely different.  Some online resources may
+      instruct you to use
+      <literal>root=UUID=<replaceable>&lt;filesystem UUID&gt;</replaceable></literal>
+      instead of
+      <literal>root=PARTUUID=<replaceable>&lt;partition UUID&gt;</replaceable></literal>,
+      but doing so will require an initramfs which is beyond the scope of
+      LFS.</para>
+      <para>The name of the device node for a partition in
+      <filename class='directory'>/dev</filename> may also change (more
+      unlikely than GRUB designator change though).  You can also replace
+      paths to device nodes like <literal>/dev/sda1</literal> with
+      <literal>PARTUUID=<replaceable>&lt;partition UUID&gt;</replaceable></literal>,
+      in <filename>/etc/fstab</filename>, to avoid a potential boot failure
+      in case the device node name has changed.</para>
+    </note>
+
     <para>GRUB is an extremely powerful program and it provides a tremendous
     number of options for booting from a wide variety of devices, operating
     systems, and partition types.  There are also many options for customization