Why would you do this?
- It's fast. Over Thunderbolt, cloning a roughly 30 GB (of used space) image takes only a few minutes.
- Minimal additional cost. Sure, you probably paid money for your Macs, but this method uses only included software... and one US$40 cable.
- No external media or extra setup. You don't have to network your computer, install additional software, or have an external hard drive. You can go straight from computer to computer with just a Thunderbolt cable.
- Two Macs—one source, one target.
- Rename the hard drive on the source Mac to something unique (don't call it Macintosh HD, which is the default). Easiest way to do this is to go to Finder > Preferences and then check or tick Hard Disks under Show these items on the desktop. Then, when you see the hard drive icon appear on your desktop, you can rename it.
- A Thunderbolt cable.
- The main hard drive partition of the source Mac must be equal to or lesser in size than the target Mac hard drive. For example, if you are imaging from 250 GB to 250 GB, that's okay; if you're imaging from 250 GB to 500 GB, that's also okay; but if you're imaging from 1 TB to 500 GB, that won't work.
Note: If you're using El Capitan (10.11) or later, the procedure has changed. More details at Cloning an image using Thunderbolt and Disk Utility (post–El Capitan)
The procedure below is for Yosemite (10.10) and earlier.
- On the target Mac, reboot the computer while holding down the T key on the keyboard to boot it into Target Disk mode. If you have done so successfully, you will see what appears to be a white lightning bolt on the screen.
- On the source Mac, reboot the computer while holding down the Cmd and R keys on the keyboard to boot into Recovery Mode.
- Then, connect the Thunderbolt cable to both Macs.
- On the source Mac, select Disk Utility from the available options.
Once Disk Utility launches up, click on the main partition (the one you renamed earlier) of the source Mac. Since Disk Utility can sometimes load up the target Mac visibly higher or lower than the source Mac, it's critical that you have them uniquely named (that's why we renamed the drive earlier). So click on that unique name.
- Click Restore. You should see the source as the uniquely-named drive.
- Then drag the main partition of the target Mac over to the Destination area.
- Click Restore.
- That's it! Once it's done, you can boot your target Mac into regular mode, and it should be a clone of your source Mac.