Bug#873958: grub-pc: False positive mixed_legacy_and_grub2 during installation on DRBD hosts

[Alex Kiousis]

Package: grub-pc
Severity: normal

Dear Maintainer,

This is a corner case for our setup but I thought i'd report it. Feel
free to close this issue if there is not trivial fix.

We have virtualization servers running Ganeti and are running VMs using
DRBD.

After dist-upgrading to Jessie we decided to upgrade from grub-legacy to
grub2.

During installation the postinst script (specifically the function
scan_grub2) detects the LV of the DRBD devices and if the VM has grub2
installed it sets mixed_legacy_and_grub2 and output a critical debconf
message. This was the case in pretty much all out hosts (we had LVs with
grub2 signatures)

Because this is a false positive and we had automated the procedure, the
message "broke" the noninteractive install of the package. We ended up
patching the postinst to ignore it.


The relevant code in the postinst script is here:
https://sources.debian.net/src/grub2/2.02~beta2-22%2Bdeb8u1/debian/postinst.in/#L126