On Sun, 30 Aug 2020 at 20:03, Rick Thomas <rick.thomas@pobox.com> wrote:
> So what am I missing? How do I tell grub on the new disk to use the root partition and volume-group on the new disk?
Hi, I have written this message from memory
without testing any of the commands, and
I don't actually use any of these commands myself
so I hope it doesn't contain any errors.
You wrote that you copied /boot. This means that you
copied the grub configuration file (/boot/grub/grub.cfg)
unchanged, so the new grub is configured to boot
the old system.
Even though you reinstalled the bootloader on the
new drive, you kept the old config file telling it to
to boot the old drive.
One answer might be to run 'update-grub' but I can't
give you exact instructions because I don't like that
aspect of grub so I prefer to write my own grub.cfg
files without all the bloat.
I expect doing that would use os-prober to generate
a new grub.cfg file with a menu that offers to boot
any of all the operating systems that os-prober finds.
I think that's the usual default method.
I think you could backup /boot/grub/grub.cfg and just try it
and see what happens. If you backup to for example
/boot/grub/grub.cfg-BACKUP then if something goes wrong
you can just enter
'configfile grub.cfg-BACKUP' at the grub> prompt to use
the old version.