Installing Debian on old ASUS motherboards

Having a couple of decommissioned ASUS motherboards (M2NPV-VM and A8N-VM CSM), as well as a 19″ cabinet with ATX cases in it, they could together be a setup for lab work, trying out Linux server stuff, as a test bed for network gear etc.

Installing Linux (Debian) is usually pretty easy, a couple of snags along the way though.
So, note to self: read this if these motherboards need to be reinstalled sometime. It will save you/myself some time.

Booting from USB flash disk

1. The BIOS of both boards need to be changed so that the flash disk is 1st disk (before the SSD also installed), and also 1st in boot order. Otherwise it will not boot from the thumb drive.
2. Install Debian as usual.
3. Once you get to the GRUB installation part of Debian install, follow the default setting and install to first disk. Which is the flash thumb drive, I know. But trying the get the Debian installer to install GRUB anywhere else just failed consistently – I have no idea why. Should have worked to install it to /dev/sdb (which is the SSD).
4. Reboot into recovery mode with the thumb drive still inserted (as GRUB was installed to it. remember?). You should now end up in a command line shell.
5. Do a “grub-install /dev/sdb” to install GRUB to the SSD. The devices might be different depending on the installed hardware, check with “ls /dev”, “du” and related commands, to get the device name of the SSD
6. Reboot, quickly remove the thumb drive during the reboot, and GRUB should now appear, served from the SSD.