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Connect this Mac to another Mac

  • Difficulty: Easy
  • Time required: 15 min or less
  • Extra: another Mac; USB-C, FireWire or Thunderbolt cable

Problem Overview
Starting with macOS 10.14 Mojave, Disk Drill can no longer access the startup disk of the Mac you are booting your computer from for data recovery. This is also true for macOS 10.15 Catalina. One of the workarounds is to make the boot disk work as an external (or secondary) disk to another Mac. This method is called Target Disk Mode, it is fast, easy and absolutely safe.
Note: Target Disk Mode is Apple’s official recommended method for high-speed data transfer and emergency file access, as well as the preferred connection option for Migration Assistant.
Here’s How
Step #1: Cable connection
To make your Mac appear as an external disk on another Mac, connect both Mac computers with a FireWire, Thunderbolt, or USB-C cable.
Step #2: Go to System Preferences
On your Mac requiring data recovery (the one you’ll be using as a disk), go to System Preferences and click Startup Disk and then – Target Disk Mode. If you see a closed lock at the lower left, click it and type your password to make the Target Disk Mode button available. Confirm by clicking Restart.
Target Disk Mode
Alternatively, press and hold the T button immediately after pressing the power button to turn on your Mac, or immediately after your Mac begins to restart. Keep holding it until it boots in Target Disk Mode.
Step #3: Run Disk Drill on the other Mac
After your local Mac starts up in Target Disk Mode, it appears as a disk icon on the desktop of the other Mac. Run Disk Drill on the host Mac and select the target Mac’s disk in the disk list to start the scan usually as if you are recovering lost data from an external disk.
Step #4: Complete scan & recovery
Proceed with data recovery normally. Once done, eject the disk by dragging its icon to the Trash (the Trash icon changes to an Eject icon).
Congratulations! It’s a success.
Final step: Disconnect your Macs
To exit Target Disk Mode, press and hold the power button on the Mac you used as a disk. Then disconnect the cable and return to normal operation.
Yes. TDM was introduced with the original PowerBook 100, and it was never removed from macOS. Check this Wikipedia article for more details.
Target Disk Mode can be tricky if you are trying to connect an older Mac to a newer one, or even if macOS versions are slightly different. To add to the mess, not all USB-C cables are compatible. Unfortunately, this level of troubleshooting is beyond the scope of this article, but these are the two potential issues to look into: try a different/better cable, or if possible, try to match the macOS versions.
.updated: March 17, 2020 author: CleverFiles Team