I finally gave up on MacOS for a Mac mini server I have and wiped it and installed Ubuntu 14.04LTS. It mostly went pretty smoothly, Ubuntu makes bootable images for Mac hardware that work fine off of USB keys. And I just wiped the whole disk and removed any vestiges of the MacOS boot loader, I imagine it’s a bit trickier if you care to preserve MacOS.
The one real problem I ran into was the new system hung at boot right after adding swap. That error is a red herring though; really it’s hanging trying to change video modes. Dumb, particularly the lack of a useful console message. The solution is to add nomodeset to the kernel command line in GRUB.
Also a few minor problems. The WiFi adapter doesn’t work, of course, although maybe the non-free drivers I was advised I could install fix that. Ubuntu’s automagic partitioner doesn’t give you a way to resize the swap partition, you’re stuck with it being the size of system RAM. And it did enough other magic things on repartitioning I was afraid to try to roll my own.
I’m pretty unimpressed with how slow this Mini is, now that I have an OS I understand on it. The Plex server seems OK, and it can transcode 1080p video at 5x real time or better. But trying to rsync 300GB of files over gigabit ethernet to it basically pegged the machine; the poor SSH process with the network connection was using 50% CPU even after I told it to use arcfour encryption, supposedly the fastest available. And terminal responsiveness was like 10 seconds at a time, although maybe it’s partly the Linux scheduler to blame for that. Anyway the system has a i5-3210M CPU which apparently is pretty weak, despite having 2 honest cores in it. Will be fine for a file server but I’m glad I built a beefy compute server for real work.