Home > Questions

Can't write to APFS external hard drive on M1 Mac mini

I have tried two different external hard drives and they are both read-only on my M1 Mac mini running macOS 12.3.1. It's strange that Time Machine can complete backups but I can't write to them. Also, when I connect them to my old iMac, I can read and write to them without any issues.

Best Answered by

Jenny Zeng

Answered on Tuesday, August 27, 2024

Apple has made Time Machine backup disks read-only to protect the integrity of the backups. The whole disk is reserved for Time Machine only. If you want to write other files to a Time Machine backup drive, you must add another APFS volume to it. Here's how to do it:

  1. Open Time Machine Settings/Preferences.
  2. Select the APFS external hard drive and click the remove button ( - ).
  3. Click "Forget Destination."
  4. Open Disk Utility.
  5. Select your APFS container and click the add button ( + ) above "Volume."
  6. Name it and click Add.

Now, you can save files to the Time Machine drives.