Home / Apple / “Time Machine needs to delete your existing backup history and start a new backup to correct it.” why?

“Time Machine needs to delete your existing backup history and start a new backup to correct it.” why?



I have this message since two days ago:

“Time Machine detected that your backups on” SynologyDS216.local “could not be reliably restored.”

“Time Machine needs to delete your existing backup history and start a new backup to correct it.”

But I can access the backup history just fine. NAS (which is a RAID 1 array) is also good.

When I look at the backups:

~ ᐅ tmutil listbackups | tail -n 5
2020-10-15-144522
2020-10-15-151447
2020-10-15-154125
2020-10-15-184439
2020-10-15-195406

we can see that it stopped backing up exactly 2 days ago.

so I decided to do a check:

tmutil verifychecksums /Volumes/Time Machine Backups/Backups.backupdb/Thomas-MBP

and an error that occurred is:

/Volumes/Time Machine Backups/Backups.backupdb/Thomas-MBP/2020-07-08-200220/Macintosh HD/System/Library/DirectoryServices/DefaultLocalDB/Default: error 257 enumerating path

The directory exists:

total 0
drwxr-xr-x@ 3 root  wheel   1
02B Aug 25 2019 . drwxr-xr-x@ 5 root wheel 170B Sep 29 2019 .. drwx------+ 7 root wheel 238B Aug 25 2019 Default

but the permits are a problem. This file has extended attributes, so I’ll see what happens:

/Volumes/Time Machine Backups/Backups.backupdb/Thomas-MBP/2020-07-08-200220/Macintosh HD/System/Library/DirectoryServices/DefaultLocalDB ᐅ sudo ls -le Default
total 0
drwx------@ 2 root  wheel   340 Aug 25  2019 aliases
 0: group:everyone deny add_file,delete,add_subdirectory,delete_child,writeattr,writeextattr,chown
drwx------@ 2 root  wheel   102 Aug 25  2019 computers
 0: group:everyone deny add_file,delete,add_subdirectory,delete_child,writeattr,writeextattr,chown
drwx------@ 2 root  wheel  4420 Aug 25  2019 groups
 0: group:everyone deny add_file,delete,add_subdirectory,delete_child,writeattr,writeextattr,chown
drwx------@ 2 root  wheel   102 Aug 25  2019 networks
 0: group:everyone deny add_file,delete,add_subdirectory,delete_child,writeattr,writeextattr,chown
drwx------@ 2 root  wheel  3468 Aug 25  2019 users
 0: group:everyone deny add_file,delete,add_subdirectory,delete_child,writeattr,writeextattr,chown

when viewing the host:

/System/Library/DirectoryServices/DefaultLocalDB ᐅ ls -l

    total 0
    drwxr-xr-x  3 root  wheel    96B Jan  1  2020 .
    drwxr-xr-x  5 root  wheel   160B Jan  1  2020 ..
    drwx------  7 root  wheel   224B Jan  1  2020 Default

The permissions are not the same and the data is available.

It appears that TimeMachine claims that it cannot use the backup due to some permission issues …

I tried to ask about it on the Apple forums, but my post was removed because I’m running a beta version of the operating system …

Has anyone seen this problem before?


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