Help: disk swap

[tony <lists@vanderhoff.org>]

Hi,

I turned on my main home server after a few weeks absence,  and got
smoke from its power supply. Fortunately, I have a backup system, which
does work; both are running Debian 10, so I swapped use to that machine.
and am able to work with that, but some of the files and settings are a
bit out of date.

I decided to move the disk from the broken machine to the backup, but on
booting I'm dropped into a grub screen saying disk id <blablabla> not
found. Not entirely surprising perhaps.

So, how do I get it to recognize, and boot from the old disK.

Cheers, Tony