Mac – Unable to backup macbook using time machine

backuptime-machine

Since a few weeks ago, i am unable to backup my mac using time machine. It finds my backup drive, but each time i get a message that reads : failed to create a local snapshot.

I have already reinstalled a fresh installation using the apple recovery utility, and also tried to use a different backup drive.
Note that i did not try to erase my data yet.

Edit:
I wanted to point out the fact that this issue is impacting two macbook at this time, while six others are being backed up fine, using the same release and the same backup disc.

Edit:
Using this command sudo tmutil listlocalsnapshots /, I get this output:

Snapshots for volume group containing disk /:
com.apple.TimeMachine.2020-06-18-194222.local
com.apple.TimeMachine.2020-06-18-203811.local
com.apple.TimeMachine.2020-06-18-213808.local
com.apple.TimeMachine.2020-06-18-223858.local
com.apple.TimeMachine.2020-06-18-233809.local
com.apple.TimeMachine.2020-06-19-004440.local
com.apple.TimeMachine.2020-06-19-014255.local
com.apple.TimeMachine.2020-06-19-024125.local
com.apple.TimeMachine.2020-06-19-033808.local
com.apple.TimeMachine.2020-06-19-043810.local
com.apple.TimeMachine.2020-06-19-053809.local
com.apple.TimeMachine.2020-06-19-064356.local
com.apple.TimeMachine.2020-06-19-083809.local
com.apple.TimeMachine.2020-06-19-095017.local
com.apple.TimeMachine.2020-06-19-104256.local

So, snapshots are indeed created despite time-machine's error message.

Best Answer

Timemachine has changed a lot between different OSX versions. Some settings were still linked to an old version. The root cause appears in the Console logs. You can filter Timemachine error in Console.app by searching backupd.

In this particular case, we've figure out the error was: Illegal permissions or ownership discovered on local snapshot directory !

We've removed the local snapshot folder: solution from Macrumors

1. command-r boot to recovery
2. csrutil disable in Terminal to disable SIP
3. reboot to command-r recovery again
4. in Terminal cd /Volumes/Macintosh\ HD/Volumes (or whatever your normal boot drive is named)
5. rm -rf com.apple.TimeMachine.localsnapshots
6. csrutil enable in Terminal to enable SIP
7. reboot

And then finally, set the permissions correctly on the default "Catalina Timemachine local path":

sudo chmod -R 755 /Volumes/Macintosh\ HD/com.apple.TimeMachine.localsnapshots

And finally it works!

Main advice: Time machine error messages are not always complete. Look at logs in Console.app while triggering Backup now for full logs.

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