Bug#1038974: grub2: Update Linux erases Windows entry in boot list

[Steve McIntyre]

On Thu, Sep 21, 2023 at 03:28:44PM +0200, Julian Andres Klode wrote:
>Control: retitle -1 grub doesn't run os-prober by default anymore, so no more other OS detected
>Control: tag -1 wontfix
>
>On Fri, Jun 23, 2023 at 04:31:55PM -0400, bud wrote:
>> Package: grub2
>> Severity: important
>> File: grub2
>> X-Debbugs-Cc: budheal508 at gmail.com
>> 
>> Dear Maintainer,
>> 
>>    * What led up to the situation?
>> I installed the 2023-04-24 weekly build, downloaded the 2023-06-05 build and used that as the jigdo base to download bookworm 12.0.0
>> Then I added the 21 DVD images and synaptic suggested adding the online main repository. After apt-get update --allow-insecure-repositories, I rebooted.
>>    * What exactly did you do (or not do) that was effective (or
>>      ineffective)?
>> The computer booted into bookworm. However, the existing option to boot Windows is no longer available. Looking in the Advanced options finds the prior Linux entry. 
>> 
>> Compare Bugs #1033985, #1008294 and #250626
>> 
>>    * What was the outcome of this action?
>> Without a Windows option, there is a suggestion in bug #1033985 that os-prober will help set me reset the grub list. Otherwise, the Windows DVD will contrarily erase grub. I only added a Linux partition to this laptop to investigate a HDMI bug, as this one has HDMI, VGA and DisplayPort connectors.
>>    * What outcome did you expect instead?
>> Just because the Linux kernel has been updated, any existing entries should not be erased - except for the one being replaced. 
>> 
>> An update should not erase the settings the user or administrator has added to customize the system. This looks like a bug.
>
>The followup comment from Chris Carr made me understand that this seems
>to be about the os-prober entries. For security reasons, os-prober is
>no longer run when writing a new grub.cfg.
>
>You can either re-enable it and get exposed to any bug in grub
>filesystem implementations which will then run as root to mount
>any disk attached to the system, or add a /etc/grub.d file that
>echos additional fixed boot entries for your other OS.

Or edit /etc/default/grub and change the GRUB_DISABLE_OS_PROBER
setting there, then run "update-grub". It's up to you.

-- 
Steve McIntyre, Cambridge, UK.                                steve at einval.com
The two hard things in computing:
 * naming things
 * cache invalidation
 * off-by-one errors                  -- Stig Sandbeck Mathisen