Will differential backup be supported in the future?
8.5.3 and 8.5.4 in UrBackup - Server administration manual
Kinda of redundant with how UrBackup stores data, even though its incremental, if you delete the full back up this relies on, you can still access the incremental as UrBackup will not remove the data from the server until all the incremental are deleted before it.
Differential was done so you could delete any intervening backups and as long as you had the FULL it relied on you were good, UrBackup has de-duplication so it will never remove a backup while some reference it… really every backup is FULL its only moving the changed data from the last full, even when deleting this is the case.