What are the necessities to set a mounted Time Machine-created sparsebundle as a backup vacation spot in Sequoia?

My purpose is to create a Sequoia Time Machine SMB backup goal which I may also mount on the backed up macOS in query (utilizing USB). I need to be capable of affirm that Time Machine will settle for the domestically mounted sparsebundle as a backup goal, ideally earlier than investing time in a big preliminary backup (I can not wait hours for an preliminary backup each time throughout trial-and-error). My efforts finish in tmutil giving an error 45.

Technique

1. I let Sequoia’s Time Machine create a sparsebundle on an exterior SMB
   share
2. I let Time Machine begin the precise knowledge switch earlier than I skip the
   first backup, to make sure that the sparsebundle is totally created, with out truly having to attend for a complete full backup
3. I mount the file system that acted as host for the SMB share — which resides on USB storage and which helps UNIX file permissions — on the macOS Sequoia occasion that created the Time Machine sparsebundle
4. The sparsebundle has proprietor and group 1000:1000, i.e. the SMB consumer on the exterior SMB server. I can mount this sparsebundle with consumer 501 (my admin account). There is not a consumer 1000 on this method.
5. At this level tmutil setdestination -a /path/to/my/sparsebundle will complain with Permission denied, so I chown -R 501:0 the sparsebundle, and mount it once more.
6. Now tmutil setdestination will as a substitute report The operation couldn’t be accomplished. Operation not supported (error 45) The backup vacation spot couldn't be added.

At that time I am undecided what the issue is.

Experiments

I’ve tried numerous experiments to see what the factors are for…

• Being allowed to mount the sparsebundle (I apparently do not should be the proprietor for this, as demonstrated by mounting it whereas being owned by 1000, however once I change the proprietor to a consumer that really exists on the system (e.g. 503) then I am instantly not allowed to mount it…)
• Having the sparsebundle being mounted as writeable, as reported by Finder’s standing bar (have not succeeded but, however this does not even appear to be required to ensure that Time Machine to truly begin utilizing it, which I found by inspecting a mounted and dealing TM-bundle on Ventura)
• Including it as a backup vacation spot utilizing tmutil

I am nonetheless at a loss as to what precisely Time Machine desires. Different UNIX permissions? ACL magic? Some .plist entry?

Query

How can I be sure that a sparsebundle (APFS) created by me by way of Time Machine, over SMB, will also be mounted domestically and be accepted as a backup vacation spot? I’ve achieved it earlier than with HFS+ bundles on Mojave, and I’ve achieved it earlier than with APFS bundles on Ventura, so I am pretty assured it must be attainable by some means.

Listed here are the permissions of the sparsebundle, and as you’ll be able to see the recursive possession of 501:0 has taken place, and it is read-writeable:

$ ls -haln bundle-name.sparsebundle 
whole 156
drwxrwxr-x@ 4 501  0    12B 12 Feb 21:00 .
drwxr-xr-x  3 501  0     4B 12 Feb 20:52 ..
-rw-rw-r--@ 1 501  0   6,0K 12 Feb 20:44 .DS_Store
-rw-rw-r--@ 1 501  0   575B 13 Feb 17:44 Data.bckup
-rw-rw-r--@ 1 501  0   575B 13 Feb 17:44 Data.plist
drwxrwxr-x@ 2 501  0    13B 13 Feb 04:07 bands
-rw-rw-r--@ 1 501  0   516B 12 Feb 20:52 com.apple.TimeMachine.MachineID.plist
-rw-rw-r--@ 1 501  0   502B 12 Feb 21:00 com.apple.TimeMachine.Outcomes.plist
-rw-rw-r--@ 1 501  0   220B 12 Feb 20:53 com.apple.TimeMachine.SnapshotHistory.plist
-rw-rw-r--@ 1 501  0     0B 12 Feb 20:44 lock
drwxrwxr-x@ 2 501  0    13B 13 Feb 04:07 mapped
-rw-rw-r--@ 1 501  0     0B 12 Feb 20:44 token

I am lacking one thing.

Further experiments

• I’ve tried tmutil inheritbackup however it says my machine already owns the sparsebundle, which is accurately.
• I additionally tried taking a look at a working sparsebundle setup on a unique macOS (Ventura) set up, however it was nonetheless complicated. For instance: once I added write permissions for myself solely to the basis sparsebundle listing utilizing Finder’s Data dialog, and mounted it by double-clicking, then I may now not again as much as it (TM complained it was now “write protected”). As quickly as I eliminated that purely further write permission I used to be as soon as once more allowed to again as much as the bundle. That specific sparsebundle had a unique UNIX file proprietor than me.

Associated

• Earlier query that resulted within the conclusion that the bundle’s host quantity have to be writeable (i.e. use a driver with write help) simply to be restored from. That is not relevant on this case since I am making an attempt to do extra than simply restore, and since the host FS already is writeable. Additionally, that was earlier than Apple migrated from HFS+ to APFS for Time Machine locations, which has undoubtedly launched new necessities.