Use Firewire Target Disk Mode To Troubleshoot A Mac

Since Apple were the main driving force behind the development of Firewire, it’s no surprise that the majority of Mac’s have shipped with support for the standard. While sometimes considered the sole preserve of power-users and Mac owners concerned with the transfer of data very quickly, Firewire is actually very flexible and can also be used to help fix a troublesome Mac using Target Disk Mode.

With a Mac safely in Target Disk Mode, its hard drive contents can be read from another computer and it is essentially reduced to the role of external hard drive, from which it can be booted from, and an operating system can even be installed. Read on below for some tips on getting started with Target Disk Mode.

Getting Started

In order to use Target Disk Mode with two Mac’s, we’ll need a Firewire cable of the type 6 pin to 6 pin. With this Firewire cable ready, switch off both Mac’s and first connect the Firewire cable to the target Mac – this is the Mac which has the hard drive which we wish to read from, or write to.

Next, power on the target Mac while holding down the ‘T’ key. After a few moments, a blue screen should appear with a yellow Firewire icon – this denotes that the machine in question is in Target Disk Mode. Now plug the other end of the Firewire cable into your host Mac and power it on. Once OS X is loaded, you should be able to access your files on the target Mac and copy any needed data.

Booting From The Target Mac

If you wish to actually boot into the target Mac’s OS X, connect the two machines as outlined above, stopping short of powering on the host Mac. Once you’re ready and the target Mac is safely in Firewire Target Disk Mode, power on the host Mac and hold down the ‘alt’ or option key.

After some time, you should be presented with a boot screen, from which you may select your target Mac’s hard drive to boot from. This may not always work, depending on the compatibility of the two machines in question.

Installing OS X In The Target Mac


It can be very useful to place a Mac in Target Disk Mode if you wish to install an operating system without using the disc drive. For example, I wanted to install OS X Tiger on an old iBook Clamshell but could not because the iBook’s optical drive was broken.

By connecting the iBook Clamshell to another iBook with Firewire Target Disk Mode, I was able to use the second iBook’s optical drive to install OS X Tiger into the desired machine. This method can even be followed to install unsupported versions of OS X onto the target machine, provided the host machine supports it – just install OS X as normal, making sure to select the target Mac as the destination drive.


Whether wanting to retrieve data, boot an old computer or install an operating system, Firewire Target Disk Mode can be a very useful tool for Mac users who own more than one machine. Firewire cables are very inexpensive and can be left ready should the need arise.

Adam Williams

Adam Williams is a journalist from North Wales, regularly covering music and technology for websites such as Make Tech Easier, Mac.Appstorm, iPad.Appstorm and Fluid Radio, in addition to writing weekly content for Apple Magazine. Follow him or contact him on twitter here

Subscribe to our newsletter!

Our latest tutorials delivered straight to your inbox