Can't inherit TM backups due to image <my-mac>.sparsebundle can't be inherited because same image exists in same directory error

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Level 1

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Can't inherit TM backups due to image <my-mac>.sparsebundle can't be inherited because same image exists in same directory error

I'm using a QNAP NAS to store TimeMachine backups to. And for whatever reason, from time to time, either macOS or QNAP OS (or both) mix things up. When this happens, my Mac suddenly can't connect to the backup-share. And whenever I got it fixed (e.g. by deleting key-chain entries or changing PW on QNAP + mac users to a new one) TimeMachine often doesn't recognise the existing backups.

Until now I usually gave up after some trying-to-fix with tmutil command directly. Which means I've had to start a new backup - loosing the history, which I don't want to do.

PROBLEM DETAILS

Mac: MacBook Air 2020 M1 - macOS 14.2.1
QNAP: backup-share is accessible via SMB
TM automatic backups are disabled (due to the issues at hand)
Existing spars bundle: <qnap-nas>/<backup-share>/<mac-name>.sparsebundle
Local mount point /Volumes/<backup-share>/<mac-name>.sparsebundle

After removing the destination (via TM settings UI) I've re-added it successfully with:

sudo tmutil setdestination smb://<user:password>@smb://<qnap-nas>/<backup-share>

Then I used inheritbackup, trying to make TM reconsider existing backups in the sparsebundle with:

sudo tmutil inheritbackup /Volumes/<backup-share>/<mac-name>.sparsebundle

Which returns the following error:

The image "<mac-name>.sparsebundle" can't be inherited because another image "<mac-name>.sparsebundle" belonging to this computer already exists in the same directory.

I couldn't find any article/thread which described how to solve this issue.

A lot discuss to additionally use tmutil associatedisk mount_point snapshot_volume. But in my case there is no .backupdb file/folder to be found anywhere (nor on backup destination nor in local snapshots/.timemachine folders). So I didn't try to "associate" anything.

Unfortunately, neither the tmutil man page nor Apples TM docu provides more details on the "can't inherit image" error or how to associatedisk in cases without .backupdb. Which leaves me at a dead-end. I could imagine I might only have to change one of the UUIDs found in the <mac-name>.sparsebundle/Info.plist files (or alike). But I'm not sure which are used where/how. So in case someone else does, here the UUIDs TM has (or had) in use:

/Volumes/<backup-share>/<mac-name>.sparsebundle/Info.plist(CFBundleInfoDictionaryVersion): ee24b2ca-fd5c-4d8f-818e-cd3768df688d
/Volumes/<backup-share>/<mac-name>.sparsebundle/com.apple.TimeMachine.MachineID.plist(com.apple.backupd.HostUUID): EA3AF7B7-0A25-56EE-84BD-4BF3A5455167
tmutil's destinationinfo: A49FD3B2-4AB0-4028-B231-702E5EE0EA7F
/Volumes/.timemachine/<qnap-host-name>/: 8D5C2095-4D0E-4DF9-B327-6A5DD53C0AD6
/Volumes/.timemachine/<qnap-host-name>/8D5C2095-4D0E-4DF9-B327-6A5DD53C0AD6/<backup-share>/<mac-name>.sparsebundle/Info.plist(CFBundleInfoDictionaryVersion): ee24b2ca-fd5c-4d8f-818e-cd3768df688d

Thanks a lot in advance!

Cheers Gabriel

MacBook Air 13″, macOS 14.2

Posted on Mar 3, 2024 7:46 AM

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Answer 1

Barney-15E

Level 10

122,042 points

Mar 3, 2024 8:47 AM in response to gabrielj

Inheriting a backup implies the backup was from another Mac which you used to configure the new Mac with Migration Assistant. If you try to add a backup destination that contains a backup of that Mac, it will ask you if you want to keep using that backup instead of creating a new one.

There is nothing in the man page that indicates you should not "inherit" a backup that was made for that machine, but it does indicate there could be problems:

One machine can own multiple machine directories and sparsebundles, but it is ill-advised for them to reside in

the same place. In such a situation, which will be chosen during a backup is undefined. As a result, inheritbackup will attempt to detect possible identity collisions before making changes.

associatedisk is for local backup drives, not network backups.

setdestination should be all you need to do to re-associate it. I don't know how it will respond to finding a valid destination already there like it does in the GUI.

If when you set the destination to the share holding the sparse bundle disk image it doesn't ask if you want to continue, it likely cannot continue with that backup.

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