Dear Maintainer,


   * What led up to the situation?

my linux installation is on my second harddrive (first hdd has only the /home/
partition).
Usually (due to bad experience) I run update-grub manually after an update of
grub. (no further options or arguments)

   * What exactly did you do (or not do) that was effective (or
     ineffective)?

recently I forgot that. When I then rebooted my computer after an update of
grub, I could still select the correct kernel in the grub menu at boot, but
then grub gave an error (partition not found or similar, sorry didn't put it
down and as you can imagine I'm not keen on reproducing it).

   * What was the outcome of this action?

well, I couldn't boot my computer

   * What outcome did you expect instead?

normal boot.

I fixed it booting with grml from usb stick, mounting all partitions, chrooting
into my installation and executing `update-grub`

Could you please check if the device your firmware (BIOS/EFI/…) boots from is
really selected in the list shown by "dpkg-reconfigure grub-pc"?

I had a similar behavior (unreliable grub updates with problems every year or
so) and the root cause was that I had Grub installed on the device the
firmware executed, but Grub updated its installation on the other drive. So
whenever there was some major Grub update (I do not know the details), I had
so manually install (update) grub to my main device.
I was surprised, that I hadn't noticed this before, but from experience I can
tell that it can take quite some time to notice this.

Kind regards
Patrick

The problem is still present when recently upgrading from the stable
wheezy to the freshly stable jessie