On Fri, 23 Jan 2026 at 11:08, alain williams <[email protected]> wrote: > On Fri, Jan 23, 2026 at 09:05:20AM +0000, David wrote: > > > But, crucially, if RAID made the two disks identical, then the code that > > grub is looking for is very likely already present on the drive you have. > > Be careful: there are 2 ways of setting up RAID-1 (mirror) for a partitioned > disk: > > • mirror the entire disk, ie sda & sdb > > • mirror partition by partition, ie sda1 & sdb1; sda2 & sdb2; ... > > If the second way then unless grub-install is run on both disks then it might > only be present on one of them.
That would be a concern regarding the grub boot sector code. So I wrote above "the code that grub is looking for", to mean NOT the grub boot sector code, but rather the grub modules in the filesystem. And we know that the code that the grub boot sector code is present, because it provides the grub-rescue prompt. Also, there's not much need to be "careful" when using those grub-rescue commands, because they don't modify anything. There's a much greater need to "be careful" when using other rescue methods.
