Time Machine error while preparing backupSolved

I once had this kind of issue due to a corrupted file in my system, I tried searching for a .plist file for Time Machine but Big Sur doesn’t seem to have it, later found a terminal script to retrieve Time Machine logs:

Later I went through the logs and found a music file by The Velvet Underground which was added around the same time when this error started. So, I removed the file and everything was working fine for me.

Here are my logs:

2021-02-15 03:14:17 Failed to copy ‘/Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/iMac/2021-02-15-031417/Macintosh HD – Data/Users/user/Music/iTunes/iTunes Music/The Velvet Underground’ to ‘/Volumes/mac backup/2021-02-15-031417.inprogress/Macintosh HD – Data/Users/user/Music/iTunes/iTunes Music’, error: -48, srcErr: NO

2021-02-15 03:14:17 Failed to copy ‘/Volumes/com.apple.TimeMachine.localsnapshots/Backups.backupdb/iMac/2021-02-15-031417/Macintosh HD – Data/Users/user/Music/iTunes/iTunes Music/The Velvet Underground/1967 – The Velvet Underground & Nico/1-01 Sunday Morning.mp3‘ to ‘(null)’, error: -8062, srcErr: NO

2021-02-15 03:14:17 Failed copy from volume “Macintosh HD – Data”

So, I removed the file and everything was working fine for me. May be try checking for the same in your logs too and try clearing out such files. It might help.

Hey @famk_e ,

Thanks for the amazing insights, but I don’t seem to find any suspicious files in my logs:

2021-09-10 18:45:15.123456-0600 localhost backupd[255]: (TimeMachine) [com.apple.TimeMachine:TMSnapshotDiffer] Diffing from 3004021 to 3050946 for file:///System/Volumes/Data/

2021-09-10 18:45:15.234567-0600 localhost backupd[255]: (TimeMachine) [com.apple.TimeMachine:EventCollection] Collected 1 events. Last path seen: ‘Library/Preferences/DirectoryService’

2021-09-10 18:45:48.345678-0600 localhost backupd[255]: (TimeMachine) [com.apple.TimeMachine:EventCollection] Failed to enumerate snapshot diffs, error: Error Domain=NSPOSIXErrorDomain Code=92 “Illegal byte sequence”

2021-09-10 18:45:48.456789-0600 localhost backupd[255]: (TimeMachine) [com.apple.TimeMachine:EventCollection] Failed to collect events for “Macintosh HD – Data” (device: /dev/disk1s2 mount: ‘/System/Volumes/Data’ fsUUID: 944D69B6-B00B-4AF6-8220-DB5A47F0DB9E eventDBUUID: 30571F8E-7071-4691-9457-92D6C7843346), error Error Domain=com.apple.backupd.ErrorDomain Code=304 “(null)” UserInfo={FailedStrategy=32}

But I noticed something that there is a UUID mismatch error? And this seems to be a continuous problem. Anybody else??

Hey there,

I’ve seen this issue come up a few times, if you can’t back up to any external drive even after reformatting, it could be an OS or content issue.

First, check if any other drives are connected to your device and set to back up. If so, disconnect them and try again.

@famk_e , you’re right about excluding files. Try excluding System files and Apps in Time Machine’s Advanced Preferences, restart, and see if that helps. If you’ve already tried First Aid, another thing to try is clearing Time Machine snapshots. Open Terminal and run:

sudo tmutil thinlocalsnapshots / 999999999999999 4

(That’s fifteen 9s). Once it finishes, restart, reconnect the external drive, re-enable Time Machine, and test again.

If that doesn’t work, try deleting the Time Machine plist. Go to Finder > Go > Computer > Macintosh HD > Preferences. Save a copy of com.apple.timemachine.plist, delete it, restart, and test. Before running the command, also delete the incomplete backup in Finder:

Double-click the external drive on the Desktop or in the Finder Sidebar.

Open “Backups.backup”, open the name of your Mac, scroll to the bottom (usually), and move the tile of the incomplete backup (usually says “In Progress”). Then try the steps above.

You can also check the Time Machine status with this command:

tmutil status

Another good test is running the backup in Safe Mode or with another user account to rule out user-specific issues.

Finally, testing with another Mac or a different external drive can help pinpoint whether it’s the drive or the Mac causing the issue.

I know it’s a lot to look into, but I just hope this helps!