Xubuntu is on a three-year-old 1TB M.2 card and it has worked well for years. I think I want to change to Debian, so I downloaded the Xfce flavor of the Debian 12 ISO and burned it to a USB drive. Then I went out and bought a new 2TB M.2 drive and installed it in the computer in a spare, unused slot. I booted to the flash drive and went through the installation, specifying the new 2TB drive, creating a 200GB partition for / and 1800GB for /home. At the end the installer stopped and said it had found the Xubuntu installation, and did I want to create a dual boot? I answered 'yes,' and it said that upon booting I would have the choice of which OS to boot to. After the installation completed and I rebooted it went straight into Xubuntu; no option to boot to Debian, like the new drive wasn't even installed. While in Xubuntu I noted that the / and /home partitions on Debian had been mounted, so I looked at them and all the files appeared to be in the partitions.
The BIOS has a feature where you can choose which disk drive you want to boot to; all you have to do is hold down F12 and you will get a menu. I did so, and there was the new M.2 drive in the list, so I selected it. Unfortunately it did not boot. Instead, a few minutes later I was staring at a black screen with a flashing underscore in the upper left corner. The keyboard was inactive, and there was no mouse. I had one more trick up my sleeve - go to the the BIOS directly. In the BIOS I swapped the boot order of the drives so the new M.2 drive would be first to boot. But when I booted it still wouldn't boot Debian; all I got was the same black screen and flashing underscore. I've been reading up on how to get this to work and I haven't found the answer yet. Both drives have a separate partitions for / and /home, and each of them has a /boot/grub/grub.cfg file in the / partition. At the top of the menu entries, the one in the Debian drive has Debian and Debian-Alternative followed by 80 (believe it or not) menu entries for Xubuntu. On the Xubuntu drive the file has menu entries only for Xubuntu, although only about 20 of them. Methinks some serious tidying up is overdue, but that can wait. Maybe a command to update grub is the right way to do it. This would probably be easy to fix, if I only knew how. I'm anxiously looking for suggestions so I can look at Debian 12 on the new drive. :)
