I placed the ailing drive back on a good Linux system and mounted it as /dev/sdd1 /mnt and ran the following commands on it:
#!/bin/sh #mount the drive being repaired. Uncomment lines as needed. sudo mount /dev/sdd1 /mnt cd /mnt/boot #installing to the mounted disk sudo grub-install \ --boot-directory=/mnt/boot/ /dev/sda Installing for i386-pc platform. Installation finished. No error reported. root@wb5agz:/# But wait. There's more. root@wb5agz:/# update-grub --boot-directory=/dev/sda Unrecognized option `--boot-directory=/dev/sda' Not good. Continuing on to update initramfs. #Isolate the disk. sudo mount --bind /dev /mnt/dev sudo mount --bind /dev/pts /mnt/dev/pts sudo mount --bind /proc /mnt/proc sudo mount --bind /sys /mnt/sys That all worked. sudo chroot /mnt root@wb5agz:/# update-initramfs -c -k 4.19.0-5-686-pae That appears to work. root@wb5agz:/# update-grub Generating grub configuration file ... Found linux image: /boot/vmlinuz-4.19.0-5-686-pae Found initrd image: /boot/initrd.img-4.19.0-5-686-pae Found linux image: /boot/vmlinuz-4.9.0-9-686-pae Found initrd image: /boot/initrd.img-4.9.0-9-686-pae Now this ruins everything. Found Debian GNU/Linux 10 (buster) on /dev/sdc1 done This was a chroot environment but it appears that /dev/sdc1 was recognized as the boot source for this external drive. /dev is part of the system. The external drive normally lives in another system and is the only boot source which is why it should be /dev/sda1. Is there any way to run update-grub from grub itself? The system this external drive is meant for normally only has 1 boot drive which is the one that is currently confusing grub. If I could run install-grub and update-grub from the dead system, there would not be any other bootable drives and the only game in town would be /dev/sda for the boot record and /dev/sda1-5 for the boot drive. Understanding what is supposed to happen isn't particularly difficult but getting grub to think simple and easy Putting the drive on another system and hoping for no contamination seems to be a lot easier said than done. Martin