Bug#982591: grub-pc can't be updated non-interactively on debian/buster64

[Evgeni Golov <evgeni@debian.org>]

Package: cloud.debian.org

Ohai,

when trying to update a VM based on the debian/buster64 box from 10.4 to
10.8, grub-pc can't be upgraded non-interactively because it doesn't
know which devices to install GRUB to (grub-pc/install_devices debconf
question is empty) and that's a fatal error for GRUB.

In our environment I "fixed" that by setting
grub-pc/install_devices_empty to "true" (AKA "it's okay to not install
GRUB to any devices during upgrade"), as we don't exactly care about the
box being rebootable. However I think this should be
ultimately be fixed inside the box in a nicer way? Maybe a first-boot
script that checks what device the system booted of (sda, vda, whatever)
and sets grub-pc/install_devices to that device?

Thanks a ton for maintaing those boxes!

Evgeni