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Okay, so I recently decided to try switching my Time Machine backups over to tmutil so that I could gain more control over exactly when they ran, but also so I could run some extra stuff before and after.

Anyway, I decided to start with a simple test with a launch agent set to run the following command once an hour:

tmutil --block

I'm using the --block option to make sure job remains visibly active till the backup is done, and because I'll need it if I want to run commands afterwards. The problem I'm having however is that when the backup gets into the Finishing stage at the end, it's frequently getting stuck with backupd ramping up to 100% CPU utilisation.

Stopping the backup and running with "Backup Now" from Time Machine's menu will work normally, and returning to regular Time Machine automatic backups works just fine without ever doing this.

It's only when using tmutil --block that this seems to happen, any ideas as to why?

  • You say "it's frequently getting stuck with backupd ramping up to 100% CPU utilization..." This, in and of itself is not a bad thing - I frequently have Strata 3D renderings maxing out the CPUs for hours at a time. We don't know from what you've written if you've ever actually let the Finishing stage finish. How do you know it is stuck? How long have you waited, in clock time, before giving up and stopping the job? If the process did finish properly in the past, how long did that take? If you can, try a new backup with these commands to a blank HD & see what happens. – IconDaemon Dec 3 '13 at 22:02
  • @IconDaemon thanks for responding, but the issue is that the finishing stage was sticking at 100% CPU utilisation for very long periods (an hour or more). I've actually answered the issue myself though, it seems I somehow had a leftover .inprogress backup, and Time Machine was getting stuck trying to remove it. For some reason tmutil didn't have any trouble though, so I was able to solve the problem, I just don't know why it occurred to begin with. – Haravikk Dec 5 '13 at 12:08
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I had a feeling I might have posted this too soon; just had Time Machine's normal backup do the same thing.

However, the culprit I discovered was that somehow I had a .inprogress backup that was older than the most recent backup (in fact there'd been five or six successful backups since). No idea how it got there, but sudo tmutil delete <path to .inprogress file> solved the problem.

I'm not sure if I'll mark this as the correct answer or not, as I still have no idea how I ended up with a leftover .inprogress file, or why it only started causing problems when it did, or why it didn't always affect automatic backups…

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