I have two equal-sized hard disks, and I use one to back up the other.
Sometimes, I back up the whole thing, but usually I just back up the partition that holds my current linux distribution,
and also the partition that holds my personal data.
[My disk has multiple partitions - one small one that Dell included when it shipped me the original disk with Windows XP on it (not my current disk),
WIndows XP (which stopped working when I migrated it to this new computer and drive), a linux swap partition, 5 partitions that each could have a different linux on it, and my data partition.]
The idea is, that were my usual disk to croak, I could just plug in my copy and use it.
I don't keep it plugged in - first: it saves electricity, second: it hopefully extends its life, third: I cannot accidentally mess it up (unless I confuse sda and sdb when backing it up, of course!!!), fourth: if my system gets hit by a surge or lightning, it may survive. I keep it (unconnected) in my computer tower, only connecting it for copying - but I may sometime decide to stick it in my fire-safe media chest.
One assumes that if I copy the whole thing, there would be no problem with GRUB.
[By the way, I use gddrescue, installed and run from a live-CD of Lubuntu (which since that is what I use, is usually lying around...)]
My fear is, that if my disk croaks after I did a partial copy - just the current distro and data - that GRUB might not be current, and
I would not be able to boot the copied disk.
Is there some way to "guarantee" that even if I do a partial copy, I would still have a bootable disk?
I don't know where GRUB is stored (possibly in two places, since it is in two stages, I believe...)
Any helpful hints on how to make my situation more likely to succeed?