ARCHIVED: How do I use my Mac as an external hard disk for another computer?

This content has been archived, and is no longer maintained by Indiana University. Information here may no longer be accurate, and links may no longer be available or reliable.

To make a Mac act as an external hard disk, you can put it in Target Disk Mode and connect it to another Mac with a FireWire or Thunderbolt cable, as follows:

Note: Target Disk Mode is available on most recent Macs; however, computers that do not have FireWire or Thunderbolt ports are excluded.

  1. Shut down the computer you want to use as an external hard disk (i.e., the target computer). If you are using a portable computer, make sure it is running on AC power. You don't need to power down the other computer (i.e., the host computer).
  2. Connect the FireWire or Thunderbolt cable to the corresponding port of the target computer, and then connect the other end of the cable to the host computer's port. Note: If the computers have different kinds of ports (e.g., one has a FireWire 400 port while the other has a FireWire 800 or Thunderbolt port), you will also need one or more adapters.
  3. Start up the target computer and hold down the letter t on its keyboard. Its drive will spin up, and its icon should appear on the host computer. The target computer's display will show a moving icon.

Alternatively, you can do the following:

  1. From the Apple menu, select System Preferences....
  2. In System Preferences, from the View menu, select Startup Disk.
  3. In the Startup Disk preference pane, click Target Disk Mode....

To exit Target Disk Mode, on the host computer, eject the target computer's disk, and then shut down the target computer. Disconnect the cable, and then start up the target computer; it will boot normally.

This is document aahs in the Knowledge Base.
Last modified on 2018-01-18 10:37:17.

Contact us

For help or to comment, email the UITS Support Center.