When using a Mac Mini as a server or router, it is very nice if the machine automatically boots if a power failure has occurred.
User chirhoxi on the ubuntu forum found out how this can be achieved:
http://ubuntuforums.org/showthread.php?t=1209576
Basically you need one of these commands:
Original Mac Mini:
setpci -s 00:03.0 0xa4.b=0
Newer Mac Mini:
setpci -s 00:03.0 0x7b.b=19
These commands might not work with the latest Mac Minis but the thread discusses how to determine for yourself what the appropriate command is.