PCs

Boot a sick Mac into Target Disk Mode for troubleshooting

William Jones shows you how to use one Mac to access the internal drive of another -- no screwdriver required.

Here's a look at how to use one Mac to access the internal drive of another -- no screwdriver required.

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Apple's Macs have one feature that, as a support tech, I would like to see other manufacturers crib for their computers. That feature is the Target Disk Mode built into the Mac firmware. With Target Disk Mode, you can use a recent Mac to access the main internal hard disk in another recent Apple machine without having to crack a case or turn a screw. All you will need is a 6-pin to 6-pin IEEE 1394 -- commonly known as a "FireWire" -- cable. Here's how you can take advantage of this capability:

  • First, if the Mac you want to access as your target is powered on, shut it down.
  • Connect your target Mac to the host Mac using your 6-pin FireWire cable.
  • Then, power on the target Mac while holding the T key on that system's keyboard.
  • Once the slave Mac has finished booting up, if you've found Target Disk Mode correctly, you should see the FireWire icon appear on the target Mac's screen. (The icon will look like a Y with a circle in the center.)
  • The target's internal disk should appear on your host Mac's desktop as an external drive. You can then treat the target disk as you would any other external FireWire drive.
  • When you are finished using the Mac in Target Disk Mode, you can unmount it and power down the target computer by pressing its power button.

This trick is great for fishing files off of a machine that can't boot OS X correctly, since it operates independently of the Mac's installed operating system. In Target Disk Mode, you can access the target computer's drive with the same freedom you would have with any other disk connected over FireWire. You can run drive diagnostics, copy files to and from the volume, and even format the device. Target Disk Mode can be a real lifesaver in an emergency.

2 comments
williamjones
williamjones

Apple has released their new upgrades to their laptop line, and FireWire ports are starting to disappear from some Macs. Target Disk Mode was an asset when you could count on every Mac having FireWire, but if Apple stops using that bus on their hardware, I can't see them continuing to include Target Disk Mode in their systems' firmware. Intel-based Macs can boot from external USB devices, so any tech that wants to create a boot disk for troubleshooting can use a Mac OS X install DVD to out the OS on a key drive or portable hard disk.

williamjones
williamjones

I'm a big fan of Target Disk Mode. It's saved my bacon many times, and it think the feature is an example of the elegant engineering Apple is known for. What are some of the tricks that you think other Mac users should have to know? edited for spelling

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