I went to my Time Machine External HD and deleted one of the backups by dragging it to the trash. Now when I try to empty the trash I keep getting messages that certain folders can't be deleted because they are in use. How do I empty the trash completely? I tried opening the trash and right-clicking on the folder and choosing "Delete Immediately" but it still gives me the message that folder can't be deleted. I'm running High Sierra 10.13.5 on an iMac.

  • How about turning Time Machine off before nuking a Time Machine backup ?
    – fd0
    Commented Jul 20, 2018 at 19:32
  • When you say you "deleted one of the backups", what exactly do you mean? Are you talking about deleting the entire Backups.backupdb folder, one of the per-computer folders inside that (i.e. all backups from a particular computer), one of the timestamped folders inside one of those (i.e. a snapshot), or some file or folder within one of those? Commented Jul 20, 2018 at 19:38
  • I wasn't making a backup. My backups are scheduled for after 1:00 am. The backup folder I deleted was about in the middle of my backups. Several months ago.
    – Natsfan
    Commented Jul 20, 2018 at 19:41
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    In that case, I recommend putting the snapshot back, and then using the "Delete Backup" option within the Time Machine interface. See this previous answer Commented Jul 20, 2018 at 21:24
  • 1
    Are you doing "incremental backups"? If so, you may have effectively trashed all of them - this would be worth checking...
    – Solar Mike
    Commented Jul 21, 2018 at 7:32

1 Answer 1


Of course the problem only shows when I want to empty my trash and my related Time Machine volume is mounted. When I want to delete my trash, I temporarily unmount the TM Volume. And from now on I will not try to make extra room on my other TM back-up volumes by deleting folders from my Time Machine back-up. I will either let Time Machine automatically delete what is needed when the volume is full, or manually delete data using a method built into the Time Machine software.

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