On Thu, Jan 22, 2026 at 10:03:11AM -0700, D. R. Evans wrote: > Due to a cascading series of failures (some of hardware, some of my brain), > I find myself in the following situation:
You do not say what sort of RAID you are using, but you have 2 disks so I assume RAID-1 (mirrored disks). I also assume that you have a root file system that is a primary disk partition, ie you do not use LVM. The easiest way to recover is to boot from a bootable Debian USB memory stick or CD-ROM. Do not try to rescue, do something like below - needs work at the command line. Boot the machine to give you a desktop. Open a terminal, become root Identify the hard disk that contains your system, look at /proc/partitions. I am going to assume that it is /dev/sda with the root file system as /dev/sda1 mkdir /tmp/RFS mount /dev/sda1 /tmp/RFS Copy /dev/ to /tmp/RFS/dev/ chroot /tmp/RFS /usr/bin/bash grub-install /dev/sda sync exit reboot The above just typed, not tested. > I had a linux-raid two-drive system that was working fine for many years. > The system uses legacy BIOS booting. My notes from long ago say that both > drives had a working GRUB; but it seems that my notes were wrong: one of the > drives died without warning, leaving me with a drive with a > fully-functioning trixie (and all the user data, etc.) present, but that > drive seems to have no working GRUB in the MBR. Trying to boot it gives me a > "grub-rescue>" prompt. > > I've scoured the Internet, but have been unable to find any clear, > unambiguous, step-by-step guide as to how to make this drive remaining > functioning drive bootable, either from the "grub-rescue>" prompt or by some > other mechanism. I tried a couple of rescue disks that I located on the > Internet, but they both errored out when I attempted to "rescue" the drive. > So I've given up, at least for now, on trying to fix the problem from the > "grub-rescue>" prompt. > > I can physically remove the drive and place it on a functioning machine, and > have done so. With the drive in the functioning machine, I have checked that > indeed all the data on it (that were in the original "/" hierarchy) are > readable. So I just want to find a way to install GRUB on the MBR in a way > that will cause the disk to be bootable into the system that was on it. That > is, I want to be able to remove the disk from the functioning machine that > it's currently (temporarily) on, put the drive back in the original machine, > power on, and have the system come up as it used to (except now with just > one active drive in the RAID array). > > From there I can add a new drive to the array and get myself back a > fully-functioning two-drive RAID-based system. > > I hope that that's a pretty clear description of the problem. If more > information is needed, I can of course provide it. > > I hope that someone here understands all this GRUB-and-boot stuff better > than I do, and can provide steps that my child-like brain can follow to get > me back to a working system. > > Doc > > -- > Web: http://enginehousebooks.com/drevans > -- Alain Williams Linux/GNU Consultant - Mail systems, Web sites, Networking, Programmer, IT Lecturer. +44 (0) 787 668 0256 https://www.phcomp.co.uk/ Parliament Hill Computers. Registration Information: https://www.phcomp.co.uk/Contact.html #include <std_disclaimer.h>
