Installation is quite simple. Just follow the installation instructions from Debian. Support for the onboard devices (network, scsi) is build into the kernel.

Notes:
While partitioning the disk, keep the first sector blank. Aboot will be installed there later on.
If you encounter errors while booting the machine, check if keyboard and mouse are plugged in. At least my box won't boot without them.
Don't worry about the "blue screen" when you power on the box - thats the normal "bios" colorscheme ;)
Hit ctrl-c to access the firmware console (ARC/SRM).

Tru64/Linux dualboot