Bug#1021301: grub-pc: regression: update to 2.06-3~deb11u2 fails with gpt

[Ansgar]

On Wed, 2022-10-05 at 09:48 +0200, Ansgar wrote:
> the upgrade to grub-pc 2.06-3~deb11u2 fails:
> 
> +---
> > Setting up grub-pc (2.06-3~deb11u2) ...
> > Installing for i386-pc platform.
> > grub-install: warning: this GPT partition label contains no BIOS
> > Boot Partition; embedding won't be possible.
> > grub-install: error: embedding is not possible, but this is
> > required for cross-disk install.
> > You must correct your GRUB install devices before proceeding:
> > 
> >   DEBIAN_FRONTEND=dialog dpkg --configure grub-pc
> >   dpkg --configure -a
> > dpkg: error processing package grub-pc (--configure):
> >  installed grub-pc package post-installation script subprocess
> > returned error exit status 1
> > Errors were encountered while processing:
> >  grub-pc
> > Log ended: 2022-09-23  06:09:42
> +---
[...]
> /dev/sda uses GPT and has one partition /dev/sda1; it was created
> this way by d-i (though it has the setting to use gpt enabled).

Ah, but this was a distraction: /dev/sda isn't the boot device. The
boot device is currently /dev/sdb. That still has a DOS disk label; the
systems using GPT for the boot device as well have a small 1M partition
for BIOS boot.

So grub-install shouldn't try to install to /dev/sda, but I find
nothing in /etc referencing /dev/sda at all (except for a comment in
/etc/fstab). So I'm not sure why the system tries to install grub
there.

I now also checked /var/log/installer/syslog and when installing the
system /dev/sda and /dev/sdb were the other way around. And it looks
like that was the case before the previous reboot as well.

So possibly one of the race conditions I read about? (FWIW, this is a
VM running under VMware.)

Ansgar