I have one physical machine and two hard drives. In the beginning, I've installed an Ubuntu 16.04 LTS on each of them (without having the other hard drive attached). Everything works fine as long as I'm attaching one hard drive at a time. But now, I want to setup a dual-boot grub so that I can choose between different hard drives/installations with both hard drives attached.
I've tried update-grub
and grub-install /dev/sdb
but it didn't work. It actually detects and adds the other Ubuntu drives installation on the grub menu, but when I choose it, a blank screen with a blinking cursor appears (it also ruins the other drive's grub).
Any guides would be appreciated.