There are two ways to boot flavors of Linux on Mac hardware:
- Boot from an external device, such as a USB stick
Per answers like those provided at How-To Geek, the fundamental problem of booting non-Mac operating systems on Macs is the unique Apple EFI code.
My situation is complicated by having a 32-bit EFI on the original Mac Pro, which requires a hack even to boot a modern Mac OS X version.
Unfortunately, I’ve had little luck even on my recent Macbook Pro trying to boot from a USB drive. While Linux succeeds in the initial boot phase, it gets lost trying to start XWindows.
Supposedly, rEFInd is the relevant tool.