[PATCH] Allow user to choose between path or fs-label instead of UUID

[Pete Appleton <grub-devl-pma@catcity.dyndns.org>]

[-- Attachment #1: Type: text/plain, Size: 1337 bytes --]

Hi all,

The file attached is intended to allow a Linux user to easily specify 
whether GRUB2 should use the traditional device path (/dev/sda1) or the 
filesystem label instead of the default UUID scheme.  This functionality 
is currently supported by GRUB2 itself but the peripheral files 
(grub-mkconfig, 10-linux etc) don't directly support it, requiring the 
user to edit the distribution-supplied files on their installation with 
the potential for consequent upgrade conflicts.

This patch adds support for a new environment variable 
GRUB_DEVICE_IDENTIFICATION taking as value one of {uuid, label, path}; 
if not set or invalid then it defaults to uuid so that the current 
semantics are respected.  If set to label then the 'search' clause and 
root=XXX kernel parameter are written using file system label syntax as 
opposed to the current single behaviour of device path if 
GRUB_DISABLE_LINUX_UUID=true

This patch was written after needing the functionality in my environment 
as I frequently move filesystems around a multi-spindle system (using 
the label to keep track of them) and seeing a few articles online 
advising various modifications to distribution supplied files; I hope 
that it is deemed useful enough to get incorporated into trunk to remove 
this minor niggle with a great product.

Thanks,

Pete Appleton

[-- Attachment #2: linux_fslabel_support.patch --]
[-- Type: text/x-patch, Size: 5913 bytes --]

=== modified file 'docs/grub.texi'
--- old/docs/grub.texi	2012-07-31 22:18:57 +0000
+++ new/docs/grub.texi	2012-09-16 16:41:08 +0000
@@ -1285,6 +1285,14 @@
 the Linux kernel, using a @samp{root=UUID=...} kernel parameter.  This is
 usually more reliable, but in some cases it may not be appropriate.  To
 disable the use of UUIDs, set this option to @samp{true}.
+@samp{GRUB_DEVICE_IDENTIFICATION} governs the scheme used instead of
+the UUID, either the file system label or the traditional device path
+
+@item GRUB_DEVICE_IDENTIFICATION
+Works in conjunction with GRUB_DISABLE_LINUX_UUID to determine how the root filesystem
+will be identified for the Linux kernel.  The default value is @samp{uuid}, which will use UUIDs. 
+Other alternatives are @samp{label} to use the file system label, or @samp{path} to use
+the traditional device path (@samp{/dev/sda1})
 
 @item GRUB_DISABLE_RECOVERY
 If this option is set to @samp{true}, disable the generation of recovery

=== modified file 'util/grub-mkconfig.in'
--- old/util/grub-mkconfig.in	2012-04-07 17:49:25 +0000
+++ new/util/grub-mkconfig.in	2012-09-16 16:33:06 +0000
@@ -131,10 +131,12 @@
 # Device containing our userland.  Typically used for root= parameter.
 GRUB_DEVICE="`${grub_probe} --target=device /`"
 GRUB_DEVICE_UUID="`${grub_probe} --device ${GRUB_DEVICE} --target=fs_uuid 2> /dev/null`" || true
+GRUB_DEVICE_LABEL="`${grub_probe} --device ${GRUB_DEVICE} --target=fs_label 2> /dev/null`" || true
 
 # Device containing our /boot partition.  Usually the same as GRUB_DEVICE.
 GRUB_DEVICE_BOOT="`${grub_probe} --target=device /boot`"
 GRUB_DEVICE_BOOT_UUID="`${grub_probe} --device ${GRUB_DEVICE_BOOT} --target=fs_uuid 2> /dev/null`" || true
+GRUB_DEVICE_BOOT_LABEL="`${grub_probe} --device ${GRUB_DEVICE_BOOT} --target=fs_label 2> /dev/null`" || 
 
 # Filesystem for the device containing our userland.  Used for stuff like
 # choosing Hurd filesystem module.
@@ -170,13 +172,20 @@
 
 if [ "x${GRUB_ACTUAL_DEFAULT}" = "xsaved" ] ; then GRUB_ACTUAL_DEFAULT="`"${grub_editenv}" - list | sed -n '/^saved_entry=/ s,^saved_entry=,,p'`" ; fi
 
+# Default to UUID if GRUB_DEVICE_IDENTIFICATION is undefined or unrecognised
+if [ "x${GRUB_DEVICE_IDENTIFICATION}" = "x" ] ; then GRUB_DEVICE_IDENTIFICATION="uuid" ; fi
+if [ "${GRUB_DEVICE_IDENTIFICATION}" != "uuid" -a "${GRUB_DEVICE_IDENTIFICATION}" != "label" -a "${GRUB_DEVICE_IDENTIFICATION}" != "path" ] ; then
+    GRUB_DEVICE_IDENTIFICATION="uuid"
+fi
 
 # These are defined in this script, export them here so that user can
 # override them.
 export GRUB_DEVICE \
   GRUB_DEVICE_UUID \
+  GRUB_DEVICE_LABEL \
   GRUB_DEVICE_BOOT \
   GRUB_DEVICE_BOOT_UUID \
+  GRUB_DEVICE_BOOT_LABEL \
   GRUB_FS \
   GRUB_FONT \
   GRUB_PRELOAD_MODULES \

=== modified file 'util/grub-mkconfig_lib.in'
--- old/util/grub-mkconfig_lib.in	2012-07-22 18:02:17 +0000
+++ new/util/grub-mkconfig_lib.in	2012-09-16 16:15:50 +0000
@@ -146,22 +146,30 @@
       done
   fi
 
-  # If there's a filesystem UUID that GRUB is capable of identifying, use it;
+  # If there's a filesystem UUID or label that GRUB is capable of identifying, use it according to GRUB_DEVICE_IDENTIFICATION
   # otherwise set root as per value in device.map.
   fs_hint="`"${grub_probe}" --device "${device}" --target=compatibility_hint`"
   if [ "x$fs_hint" != x ]; then
     echo "set root='$fs_hint'"
   fi
-  if fs_uuid="`"${grub_probe}" --device "${device}" --target=fs_uuid 2> /dev/null`" ; then
+  if [ "x${GRUB_DEVICE_IDENTIFICATION}" = "xlabel" ] && fs_label="`"${grub_probe}" --device "${device}" --target=fs_label 2> /dev/null`" ; then
     hints="`"${grub_probe}" --device "${device}" --target=hints_string 2> /dev/null`" || hints=
     echo "if [ x\$feature_platform_search_hint = xy ]; then"
-    echo "  search --no-floppy --fs-uuid --set=root ${hints} ${fs_uuid}"
+    echo "  search --no-floppy --label --set=root ${hints} ${fs_label}"
     echo "else"
-    echo "  search --no-floppy --fs-uuid --set=root ${fs_uuid}"
+    echo "  search --no-floppy --label --set=root ${fs_label}"
     echo "fi"
+  else
+    if fs_uuid="`"${grub_probe}" --device "${device}" --target=fs_uuid 2> /dev/null`" ; then
+      hints="`"${grub_probe}" --device "${device}" --target=hints_string 2> /dev/null`" || hints=
+      echo "if [ x\$feature_platform_search_hint = xy ]; then"
+      echo "  search --no-floppy --fs-uuid --set=root ${hints} ${fs_uuid}"
+      echo "else"
+      echo "  search --no-floppy --fs-uuid --set=root ${fs_uuid}"
+      echo "fi"
+    fi
   fi
 }
-
 grub_get_device_id ()
 {
   device="$1"

=== modified file 'util/grub.d/10_linux.in'
--- old/util/grub.d/10_linux.in	2012-07-22 18:02:17 +0000
+++ new/util/grub.d/10_linux.in	2012-09-16 16:21:41 +0000
@@ -43,13 +43,27 @@
   ;;
 esac
 
-if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
-    || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
-    || uses_abstraction "${GRUB_DEVICE}" lvm; then
-  LINUX_ROOT_DEVICE=${GRUB_DEVICE}
-else
-  LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
-fi
+case x"$GRUB_DEVICE_IDENTIFICATION" in
+    xpath)
+        LINUX_ROOT_DEVICE=${GRUB_DEVICE}
+        ;;
+    xlabel)
+        if [ "x${GRUB_DEVICE_LABEL}" = "x" ] \
+            || ! test -e "/dev/disk/by-label/${GRUB_DEVICE_LABEL}" \
+            || uses_abstraction "${GRUB_DEVICE}" lvm; then
+            LINUX_ROOT_DEVICE=${GRUB_DEVICE}
+        else
+            LINUX_ROOT_DEVICE=LABEL=\"${GRUB_DEVICE_LABEL}\"
+        fi;;
+    *)
+        if [ "x{GRUB_DEVICE_UUID}" = "x" ] \
+            || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
+            || uses_abstraction "${GRUB_DEVICE}" lvm; then
+            LINUX_ROOT_DEVICE=${GRUB_DEVICE}
+        else
+            LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
+        fi;;      
+esac
 
 GRUBFS="`${grub_probe} --device ${GRUB_DEVICE} --target=fs 2>/dev/null || true`"