On Thu 29 Jan 2026 at 16:59:37 (-0700), D. R. Evans wrote: > D. R. Evans wrote on 1/29/26 4:53 PM: > > David wrote on 1/29/26 3:55 PM: > > > > > to read in the root directory of each device in turn. Can you please > > > report the result of these interactive grub-rescue commands, after booting > > > your system with only the drive being rescued connnected: > > > > > > ls (hd0)/ > > > ls (hd0, msdos1)/ > > > ls (hd0, msdos2)/ > > > ls (md/0)/ > > > > > > > They all return: > > error: unknown filesystem > > FWIW (which may be nothing), when I used a couple of GRUB rescue disks > before first posting here, they both trundled and thought for a bit, > then errored out with a similar message.
That's worrying. A Grub rescue prompt could well fail because it needs modules to read the filesystems, but needs to read the filesystems to find its modules, which is why it needs a human to help it search every nook and cranny of all the devices for some modules to load. But a Grub Rescue disk should be complete and need no modules from elsewhere. I wondered, knowing nothing about RAID, whether the partition has some metadata at the start, before the actual ext4 (or whatever) filesystem starts. I don't even know whether Grub has the ability to look at partitions in that way. You've examined this disk when another disk is booted in the machine, haven't you? I don't know whether there are mdadm options to list these sorts of parameters. Cheers, David.
