Re: [PATCH v3] Add GRUB_DISABLE_UUID

[Daniel Kiper]

Adding Nicholas...

On Tue, Oct 22, 2019 at 10:44:28AM +0200, Javier Martinez Canillas wrote:
> From: Peter Jones <address@hidden>
>
> The grub-mkconfig and 10_linux scripts by default attempt to use a UUID to
> set the root kernel command line parameter and the $root GRUB environment
> variable.
>
> The former can be disabled by setting the GRUB_DISABLE_LINUX_UUID variable
> to "true", but there is currently no way to disable the latter.
>
> The generated grub config uses the search command with the --fs-uuid option
> to find the device that has to be set as $root, i.e:
>
>  search --no-floppy --fs-uuid --set=root ...
>
> This is usually more reliable but in some cases it may not be appropriate,
> so this patch introduces a new GRUB_DISABLE_UUID variable that can be used
> to disable searching for the $root device by filesystem UUID.
>
> When disabled, the $root device will be set to the value specified in the
> device.map as found by the grub-probe --target=compatibility_hint option.
>
> When setting GRUB_DISABLE_UUID=true, the GRUB_DISABLE_LINUX_UUID and
> GRUB_DISABLE_LINUX_PARTUUID variables will also be set to "true" unless
> these have been explicitly set to "false".
>
> That way, the GRUB_DISABLE_UUID variable can be used to force using the
> device names for both GRUB and Linux.
>
> Signed-off-by: Peter Jones <address@hidden>
> Signed-off-by: Javier Martinez Canillas <address@hidden>
> Reviewed-by: Daniel Kiper <address@hidden>

Nicholas, are you OK with that patch right now? If yes and you could
add your RB that would be perfect.

> ---
>
> Changes in v3:
> - Make the patch more consistent with the logic in commit 51be3372ec8
>   ("templates: Update grub script template files").
> - Add Reviewed-by tag from Daniel Kiper.
>
> Changes in v2:
> - Explain better in the commit message why the GRUB_DISABLE_UUID variable
>   is needed and the difference with the existing GRUB_DISABLE_LINUX_UUID/
>   GRUB_DISABLE_LINUX_PARTUUID variables.
> - Remove logic that disabled setting the root cmdline param to either the
>   filesystem UUID or partition UUID and instead use the existing variables
>   to disable this.
>
>  docs/grub.texi            |  9 +++++++++
>  util/grub-mkconfig.in     | 10 ++++++++++
>  util/grub-mkconfig_lib.in |  4 ++--
>  3 files changed, 21 insertions(+), 2 deletions(-)
>
> diff --git a/docs/grub.texi b/docs/grub.texi
> index d788efe440f..c25ab7a5fe7 100644
> --- a/docs/grub.texi
> +++ b/docs/grub.texi
> @@ -1441,6 +1441,15 @@ enable the use of partition UUIDs, set this option to 
> @samp{false}.
>  If this option is set to @samp{true}, disable the generation of recovery
>  mode menu entries.
>
> +@item GRUB_DISABLE_UUID
> +Normally, @command{grub-mkconfig} will generate menu entries that use
> +universally-unique identifiers (UUIDs) to identify various filesystems to
> +search for files.  This is usually more reliable, but in some cases it may
> +not be appropriate.  To disable this use of UUIDs, set this option to
> +@samp{true}. Setting this option to @samp{true}, will also set the options
> +@samp{GRUB_DISABLE_LINUX_UUID} and @samp{GRUB_DISABLE_LINUX_PARTUUID} to
> +@samp{true}, unless they have been explicilty set to @samp{false}.
> +
>  @item GRUB_VIDEO_BACKEND
>  If graphical video support is required, either because the @samp{gfxterm}
>  graphical terminal is in use or because @samp{GRUB_GFXPAYLOAD_LINUX} is set,
> diff --git a/util/grub-mkconfig.in b/util/grub-mkconfig.in
> index a6ce375ed18..fb7fd4902f4 100644
> --- a/util/grub-mkconfig.in
> +++ b/util/grub-mkconfig.in
> @@ -158,6 +158,15 @@ if test -f ${sysconfdir}/default/grub ; then
>    . ${sysconfdir}/default/grub
>  fi
>
> +if [ "x${GRUB_DISABLE_UUID}" = "xtrue" ]; then
> +  if [ -z "${GRUB_DISABLE_LINUX_UUID}" ]; then
> +    GRUB_DISABLE_LINUX_UUID="true"
> +  fi
> +  if [ -z "${GRUB_DISABLE_LINUX_PARTUUID}" ]; then
> +    GRUB_DISABLE_LINUX_PARTUUID="true"
> +  fi
> +fi
> +
>  # XXX: should this be deprecated at some point?
>  if [ "x${GRUB_TERMINAL}" != "x" ] ; then
>    GRUB_TERMINAL_INPUT="${GRUB_TERMINAL}"
> @@ -227,6 +236,7 @@ export GRUB_DEFAULT \
>    GRUB_DISABLE_LINUX_UUID \
>    GRUB_DISABLE_LINUX_PARTUUID \
>    GRUB_DISABLE_RECOVERY \
> +  GRUB_DISABLE_UUID \

I will move this before GRUB_DISABLE_LINUX_UUID before committing.
I hope this is not a problem for you.

Daniel