HELP upgrade 10.3 to 11.2, now it won't boot!

[Dave]

On Tuesday 11 September 2018 21:24:38 Rick Miller wrote:
> You may be able to resolve it by booting the system to external media and
> mounting the disk with the root filesystem and modifying /etc/fstab.

That's how I fixed mine.  When I did the 10.3 to 11.2 upgrade I got
the same (or very similar) and it seems that 11 enumerates the disk
in a different fashion to 10.  Sadly, I didn't note down the precise
difference to can't report on what may have happened.

This only happened on my file server where the boot disk is not
in MBR format.  Other boxes using MBR didn't have issues.