need to write the whole thing by hand.
@menu
-* Simple configuration:: Recommended for most users
-* Shell-like scripting:: For power users and developers
-* Multi-boot manual config:: For non-standard multi-OS scenarios
-* Embedded configuration:: Embedding a configuration file into GRUB
+* Simple configuration:: Recommended for most users
+* Root Identifcation Heuristics:: Summary on how the root file system is identified.
+* Shell-like scripting:: For power users and developers
+* Multi-boot manual config:: For non-standard multi-OS scenarios
+* Embedded configuration:: Embedding a configuration file into GRUB
@end menu
usually more reliable, but in some cases it may not be appropriate. To
disable the use of UUIDs, set this option to @samp{true}.
+@item GRUB_DISABLE_LINUX_PARTUUID
+If @command{grub-mkconfig} cannot identify the root filesystem via its
+universally-unique indentifier (UUID), @command{grub-mkconfig} can use the UUID
+of the partition containing the filesystem to identify the root filesystem to
+the Linux kernel via a @samp{root=PARTUUID=...} kernel parameter. This is not
+as reliable as using the filesystem UUID, but is more reliable than using the
+Linux device names. When @samp{GRUB_DISABLE_LINUX_PARTUUID} is set to
+@samp{false}, the Linux kernel version must be 2.6.37 (3.10 for systems using
+the MSDOS partition scheme) or newer. This option defaults to @samp{true}. To
+enable the use of partition UUIDs, set this option to @samp{false}.
+
@item GRUB_DISABLE_RECOVERY
If this option is set to @samp{true}, disable the generation of recovery
mode menu entries.
menu entries; simply type the menu entries you want to add at the end of
that file, making sure to leave at least the first two lines intact.
+@node Root Identifcation Heuristics
+@section Root Identifcation Heuristics
+If the target operating system uses the Linux kernel, @command{grub-mkconfig}
+attempts to identify the root file system via a heuristic algoirthm. This
+algorithm selects the identification method of the root file system by
+considering three factors. The first is if an initrd for the target operating
+system is also present. The second is @samp{GRUB_DISABLE_LINUX_UUID} and if set
+to @samp{true}, prevents @command{grub-mkconfig} from identifying the root file
+system by its UUID. The third is @samp{GRUB_DISABLE_LINUX_PARTUUID} and if set
+to @samp{true}, prevents @command{grub-mkconfig} from identifying the root file
+system via the UUID of its enclosing partition. If the variables are assigned
+any other value, that value is considered equivalent to @samp{false}. The
+variables are also considered to be set to @samp{false} if they are not set.
+
+When booting, the Linux kernel will delegate the task of mounting the root
+filesystem to the initrd. Most initrd images determine the root file system by
+checking the Linux kernel's command-line for the @samp{root} key and use its
+value as the identification method of the root file system. To improve the
+reliability of booting, most initrd images also allow the root file system to be
+identified by its UUID. Because of this behavior, the @command{grub-mkconfig}
+command will set @samp{root} to @samp{root=UUID=...} to provide the initrd with
+the filesystem UUID of the root file system.
+
+If no initrd is detected or @samp{GRUB_DISABLE_LINUX_UUID} is set to @samp{true}
+then @command{grub-command} will identify the root filesystem by setting the
+kernel command-line variable @samp{root} to @samp{root=PARTUUID=...} unless
+@samp{GRUB_DISABLE_LINUX_PARTUUID} is also set to @samp{true}. If
+@samp{GRUB_DISABLE_LINUX_PARTUUID} is also set to @samp{true},
+@command{grub-command} will identify by its Linux device name.
+
+The following table summarizes the behavior of the @command{grub-mkconfig}
+command.
+
+@multitable {detected} {GRUB_DISABLE_LINUX_PARTUUID} {GRUB_DISABLE_LINUX_UUID} {Linux Root}
+@headitem Initrd detected @tab GRUB_DISABLE_LINUX_PARTUUID Set To @tab GRUB_DISABLE_LINUX_UUID Set To @tab Linux Root ID Method
+@item false @tab false @tab false @tab part UUID
+@item false @tab false @tab true @tab part UUID
+@item false @tab true @tab false @tab dev name
+@item false @tab true @tab true @tab dev name
+@item true @tab false @tab false @tab fs UUID
+@item true @tab false @tab true @tab part UUID
+@item true @tab true @tab false @tab fs UUID
+@item true @tab true @tab true @tab dev name
+@end multitable
+
+Remember, @samp{GRUB_DISABLE_LINUX_PARTUUID} and @samp{GRUB_DISABLE_LINUX_UUID}
+are also considered to be set to @samp{false} when they are unset.
@node Shell-like scripting
@section Writing full configuration files directly
;;
esac
+# Default to disabling partition uuid support to maintian compatibility with
+# older kernels.
+GRUB_DISABLE_LINUX_PARTUUID=${GRUB_DISABLE_LINUX_PARTUUID-true}
+
# btrfs may reside on multiple devices. We cannot pass them as value of root= parameter
# and mounting btrfs requires user space scanning, so force UUID in this case.
-if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
- || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
+if ( [ "x${GRUB_DEVICE_UUID}" = "x" ] && [ "x${GRUB_DEVICE_PARTUUID}" = "x" ) \
+ || ( [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
+ && [ "x${GRUB_DISABLE_LINUX_PARTUUID}" = "xtrue" ] ) \
+ || ( ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
+ && ! test -e "/dev/disk/by-partuuid/${GRUB_DEVICE_PARTUUID}" ) \
|| ( test -e "${GRUB_DEVICE}" && uses_abstraction "${GRUB_DEVICE}" lvm ); then
LINUX_ROOT_DEVICE=${GRUB_DEVICE}
+elif [ "x${GRUB_DEVICE_UUID}" = "x" ] \
+ || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ]; then
+ LINUX_ROOT_DEVICE=PARTUUID=${GRUB_DEVICE_PARTUUID}
else
LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
fi
if test -z "${initramfs}" && test -z "${initrd_real}" ; then
# "UUID=" and "ZFS=" magic is parsed by initrd or initramfs. Since there's
# no initrd or builtin initramfs, it can't work here.
- linux_root_device_thisversion=${GRUB_DEVICE}
+ if [ "x${GRUB_DEVICE_PARTUUID}" = "x" ] \
+ || [ "x${GRUB_DISABLE_LINUX_PARTUUID}" = "xtrue" ]; then
+
+ linux_root_device_thisversion=${GRUB_DEVICE}
+ else
+ linux_root_device_thisversion=PARTUUID=${GRUB_DEVICE_PARTUUID}
+ fi
fi
if [ "x$is_top_level" = xtrue ] && [ "x${GRUB_DISABLE_SUBMENU}" != xy ]; then
;;
esac
+# Default to disabling partition uuid support to maintian compatibility with
+# older kernels.
+GRUB_DISABLE_LINUX_PARTUUID=${GRUB_DISABLE_LINUX_PARTUUID-true}
+
# btrfs may reside on multiple devices. We cannot pass them as value of root= parameter
# and mounting btrfs requires user space scanning, so force UUID in this case.
-if [ "x${GRUB_DEVICE_UUID}" = "x" ] || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
- || ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
+if ( [ "x${GRUB_DEVICE_UUID}" = "x" ] && [ "x${GRUB_DEVICE_PARTUUID}" = "x" ] ) \
+ || ( [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ] \
+ && [ "x${GRUB_DISABLE_LINUX_PARTUUID}" = "xtrue" ] ) \
+ || ( ! test -e "/dev/disk/by-uuid/${GRUB_DEVICE_UUID}" \
+ && ! test -e "/dev/disk/by-partuuid/${GRUB_DEVICE_PARTUUID}" ) \
|| ( test -e "${GRUB_DEVICE}" && uses_abstraction "${GRUB_DEVICE}" lvm ); then
LINUX_ROOT_DEVICE=${GRUB_DEVICE}
+elif [ "x${GRUB_DEVICE_UUID}" = "x" ] \
+ || [ "x${GRUB_DISABLE_LINUX_UUID}" = "xtrue" ]; then
+ LINUX_ROOT_DEVICE=PARTUUID=${GRUB_DEVICE_PARTUUID}
else
LINUX_ROOT_DEVICE=UUID=${GRUB_DEVICE_UUID}
fi
gettext_printf "Found initrd image: %s\n" "${dirname}/${initrd}" >&2
else
# "UUID=" magic is parsed by initrds. Since there's no initrd, it can't work here.
- linux_root_device_thisversion=${GRUB_DEVICE}
+ if [ "x${GRUB_DEVICE_PARTUUID}" = "x" ] \
+ || [ "x${GRUB_DISABLE_LINUX_PARTUUID}" = "xtrue" ]; then
+
+ linux_root_device_thisversion=${GRUB_DEVICE}
+ else
+ linux_root_device_thisversion=PARTUUID=${GRUB_DEVICE_PARTUUID}
+ fi
fi
if [ "x$is_top_level" = xtrue ] && [ "x${GRUB_DISABLE_SUBMENU}" != xy ]; then
projects / thirdparty / grub.git / commitdiff
