I've got a VM running on an XPC-NG 8.1 host that I think was probably migrated to there from a different vm host (kvm maybe?) several years ago.

The VM is running Zentyal 6.2 which is based on Ubuntu 18.04 and I'm trying to update it to Zentyal 7, which I think also updates the base OS to 20.04.

The upgrade is failing with a message that grub-install /dev/vda failed as it's missing from the device.map. I ran grub-mkdevicemap thinking that would help but then realised that the device is /dev/xvda not /dev/vda. This is why I think the system might have originated with a different hypervisor. To back that up, if I check fstab I see a note to say that "# / was on /dev/vda1 during installation"

So, at some point during the upgrade, grub is being run and told to install it's self to /dev/vda but that doesn't exist any more, problem is that I'm struggling a bit to work out where the /dev/vda is coming from so that I can go fix it. Does anyone have any idea where I might start looking?