Mac 101: Target Disk Mode

Apple’s Target Disk Mode is an essential tool built-in to every Mac. It has become irrelevant simply because switchers today aren’t aware that it’s even there.

Apple’s primary document explaining Target Disk Mode covers nearly every Firewire equipped Mac beginning with the slot-loading iMac back in the PowerPC G3 days of 1999. Today, there are over 150 docs on Apple’s Knowledge Base that incorporate the use of Target Disk Mode in troubleshooting.

Apple obviously notices the trend that its customers are not using this powerful tool any longer. Two of Apple’s current Macs don’t even include Firewire (MacBook and MacBook Air) and this technology simply won’t work over USB.

Why would someone need this anyway? Let’s say you start up your Mac and nothing happens. There’s no login window and no boot screen at all. You hear the hard drive whirling around but that’s it. After inserting the Mac OS X disk, you can see the HDD is mounted and you only have two options. The first is to erase the disk for an OS reinstall and the other is to scan the drive for errors. Well, an error check doesn’t help and now you’re stuck with a non-booting Mac and a few important files that weren’t backed up.

On most modern Macs, pulling out the HDD and putting it in a 2.5″ external HDD enclosure will do just fine but you need those files now. All you must do is plug in a Firewire cable and connect the other end to another Mac with Firewire. Oh yeah, I forgot to mention that you must be lucky enough to have a spare Mac with Firewire laying around.

Once the two computers are connected, simply boot up the healthy Mac login. On the other computer, hold down the “T” key and hit the power button. With a little luck, the previously non-booting machine’s HDD will appear on your functioning Mac’s desktop. Voilà, you can now successfully copy those files to your working Mac and run the dead machine to an Apple Store.

Target Disk Mode is a powerful utility that can really help out in a bind. What other users for it have you found?