My rig is running Debian 8 as it's old enough to have Xorg 1.16 and Fglrx in its repo while new enough to use Systemd with support to 2020. An X session needs to be running for libatiadlxx to initialize to monitor temps, fans and reclock.
Yes, I have another rig with a IP KVM attached and that solves the problem there, but I can't get the headless rig to start mining when X is running; it craps out with the good old MIT magic cookie error. I've tried enabling remote desktop over IP but still no banana.
OK found a hack to get it working. Installed Teamviewer, started graphical desktop session, started miner from separate ssh session (not GUI), disconnected GUI session. Bit of a pain but best I've found so far.