Unlike most Macs, Mac minis and Mac Pros that are sold to be servers are supposed to come with Screen Sharing (VNC) turned on in OS X, so that you can set them up from another Mac even if you don’t have a screen and keyboard attached. This Apple Knowledgebase Article explains how.
Except we’ve now seen a couple of minis where this is definitely not the case. We were at a client today, in fact, where we had a keyboard, but no screen, and no way of remotely controlling it.
But Macs can do some awesome tricks, and one of them is Target Disk Mode, where if you hold down T when the computer starts up, instead of booting, it makes its drive available as though it were an external hard drive, connected via Thunderbolt or FireWire (either built in, or via a Thunderbolt-to-FireWire adapter). Macs without Thunderbolt or FireWire, e.g. pre-2011 MacBook Airs, don’t have Target Disk Mode.
Another nice thing about a Mac is that, unless it was released since the last update to OS X, you can boot it with any other Mac’s copy of OS X.
So that’s what we did. We started up the mini, and held down the T key on the keyboard, unable to see what we were doing. We attached a Thunderbolt cable. Then we shut down a recent vintage MacBook Air, attached the cable, and started it up with option held down, which lets you choose what drive you want to boot from. We could see the mini server’s hard drive as an available disk, and we chose it. The mini’s hard drive started up our MacBook Air, and we were able to see everything. Once we got in, we turned on Screen Sharing service and performed the rest of the setup, and (our client) lived happily ever after.