I migrated my data from an iMac to a new Mac Mini via Time Machine without problem.

However, when I try to manually run a back up I get the following message:

Disk Time Machine back up contains back ups from a different computer

Is this a bug I can fix by taking some steps other than erasing my old backups?

  • Welcome to Ask Different. If you would like to use your previous Time Machine backups with your new Mac Mini, you may find this question useful: apple.stackexchange.com/questions/32841/…. If you don't want to keep previous backups, erase the disk with Disk Utility and select it as a backup disk in System Preferences > Time Machine.
    – jaume
    Jan 12, 2022 at 11:30

2 Answers 2


I'm not sure how you migrated; in normal circumstances if you use Migration Assistant when you first fire up the new Mac, it can proceed with the existing Time Machine backups.

There are indeed steps to inherit a time machine backup, but they are hairy, and I often end up starting backups from scratch.

This issue was covered here: How can I use an existing Time Machine backup with my new computer?


Time Machine should offer you a choice to inherit the existing backup or create a new one. If it doesn't do that, try the following

  1. Go to System Preferences > Time machine
  2. Unlock by clicking on the lock
  3. Click Options...
  4. Remove the existing backup volume
  5. Now add the backup volume again
  6. Time Machine should now ask you if you want to inherit the existing backup or create a new one

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