My main problem, I think, is that I need for a brief period to have all three hard drives resident, and all in not quite the IDE locations I'd like them. I managed to copy the OS across (still Fedora Core 5, at the moment; I intend to migrate to CentOS), and was hoping to the run that copy with the old recordings mount still active while I copied that mount.
No such luck. I couldn't find my FC5 boot disc & so was using a CentOS disc as a rescue boot device, but I don't think that was the issue. For safety, I was mounting my system (under the rescue boot) read-only and running grub from the rescue CD. I guess I wasted nearly 2 hours trying to get that to boot 🙁 All I'd get was the BIOS run through, and instead of a grub menu, a black screen & a blinking cursor.
What was worse was that after I failed to do that, I tried to revert to just my old 2 discs, and I couldn't get those to boot either! I'd stuffed the MBR of the old boot disc ...
Eventually, I twigged that normally I run grub from the OS itself (under chroot /mnt/sysimage), so I tried that and it worked.
Thankfully, I can now run the old system up again, albeit with my new disc unplugged, so the morel of that story is to run grub from your OS and not the rescue disc.
I think I may need to use the more detailed install command from the grub shell instead of the grub-install shell script I normally use. I'll report back if I have any joy with that later in the week, as there's a death of examples of using grub install as opposed to grub-install (or grub setup).
I can't leave it too long, as SMART has reported the old boot disc as starting to report read errors, and I don't want that.