How to inherit sparsebundle on macOS Server Time Machine service?
As it turns out, it is super easy with a single Terminal command.

First, you need to mount the Time Machine share using Finder. Just browse to the server, then to the share so that it mounts. I mounted with Admin privileges since Admin owns the the Time Machine sparsebundle.

Then, you open Terminal and run this command:

sudo tmutil inheritbackup "/path/to/backup.sparsebundle"


For example, mine would be:

sudo tmutil inheritbackup /Volumes/Time\ Machine/MacBook\ Pro.sparesebundle


If your prefer to use quotes intead of the space escape, you should be able to do:

sudo tmutil inheritbackup "/Volumes/Time Machine/MacBook Pro.sparesebundle"


You will need to enter your Admin password, and that should do it.

I rebooted after this, then selected the backup share in Time Machine and now it's using the existing sparsebundle instead of creating a new one.