Cloning an image using Thunderbolt and Disk Utility

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.

Requirements

  • 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.

Procedure

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.

  1. lightningboltOn 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.
  2. On the source Mac, reboot the computer while holding down the Cmd and R keys on the keyboard to boot into Recovery Mode.
  3. Then, connect the Thunderbolt cable to both Macs.
  4. On the source Mac, select Disk Utility from the available options.
  5. diskutility
    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.
  6. Click Restore. You should see the source as the uniquely-named drive.
  7. Then drag the main partition of the target Mac over to the Destination area.
  8. Click Restore.
  9. 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.

8 thoughts on “Cloning an image using Thunderbolt and Disk Utility”

  1. I have two classrooms that are identical and needed to restore the instructor laptop. Was very handy to take the existing/working instructor laptop and simply clone it to the other one that had gotten corrupted.

  2. Thank you for this piece of valuable information, like the other comments I do work for a college and cloning with a thunderbolt was awesome fast.

  3. What about the computer name? do they both then have they same name? What if they are part of the same domain? What if the disk is encrypted?

  4. What about the computer name? do they both then have they same name?

    The computer share name doesn’t matter. I would recommend for the partition name actually be different so that you can easily tell which is the internal drive and which is the external drive (if they’re both called Macintosh HD, you may end up accidentally erasing your source partition). Fortunately, starting with El Capitan, Disk Utility now shows which drive is external v. internal.

    What if they are part of the same domain?

    If the source partition is on the domain, you’ll want to unplug your network cable (and disable wireless) before you do the imaging. Once the imaging is done, boot up your newly imaged drive, join it to the domain with a different computer name, and then plug in the source computer again. Otherwise you’ll get conflicts on the domain for the two objects having the same name, and one may bump the other off of AD.

    What if the disk is encrypted?

    You cannot image an encrypted drive. It has to be decrypted.

Leave a Reply

Your email address will not be published. Required fields are marked *