EDIT: Fixed. See below. Not going to delete this unless someone else wants to but leaving this for posterity of my own incompetence 
I’ve got a relatively small setup with only 5 clients on it, but I’m out of storage with only full image backups of the machines. It was working fine for weeks, creating full file backups, image backups, incrementals… then the 3TB of storage assigned to urbackup filled up and now I’m stuck.
Thing is cleanup seems to have “done its job” and removed backups in order to get everything back to decent space utilization, so now each host only has a single full image backup, the largest of which is 150GB. In total the total of the backup sizes of all these full images is around 300GB so I have 2.7TB of supposedly expired data.
I’ve tried running urbackupsrv remove-unknown and get;
[root@a5ee3f144e58 /]# urbackupsrv remove-unknown
2026-07-17 10:48:34: Going to remove all unknown files and directories in the urbackup storage directory. Waiting 20 seconds...
2026-07-17 10:48:54: Shutting down all database instances...
2026-07-17 10:48:54: Opening urbackup server database...
2026-07-17 10:48:54: Testing if backup destination can handle subvolumes and snapshots...
Cannot become root user
2026-07-17 10:48:54: Backup destination cannot handle subvolumes and snapshots. Snapshots disabled.
2026-07-17 10:48:54: Cleaning up 0 percent
2026-07-17 10:48:54: Cleaning up 0 bytes on backup storage
2026-07-17 10:48:54: Database cache size is 200 MB
2026-07-17 10:48:54: Starting cleanup...
2026-07-17 10:48:54: Freeing database connections...
2026-07-17 10:48:54: Free space: 0 bytes
2026-07-17 10:48:54: Free space: 0 bytes
2026-07-17 10:48:54: WARNING: SQLite: automatic index on backups(done) errorcode: 284
2026-07-17 10:48:54: Free space: 0 bytes
2026-07-17 10:48:54: Client with id=3 has 1 full file backups min_file_full=1
2026-07-17 10:48:54: Client with id=3 has 0 incremental file backups min_file_incr=5
2026-07-17 10:48:54: Client with id=1 has 1 full file backups min_file_full=1
2026-07-17 10:48:54: Client with id=1 has 0 incremental file backups min_file_incr=5
2026-07-17 10:48:54: Client with id=2 has 1 full file backups min_file_full=1
2026-07-17 10:48:54: Client with id=2 has 0 incremental file backups min_file_incr=5
2026-07-17 10:48:54: Client with id=4 has 1 full file backups min_file_full=1
2026-07-17 10:48:54: Client with id=4 has 0 incremental file backups min_file_incr=5
2026-07-17 10:48:54: Client with id=5 has 1 full file backups min_file_full=1
2026-07-17 10:48:54: Client with id=5 has 0 incremental file backups min_file_incr=5
2026-07-17 10:48:54: Client with id=3 has 1 full file backups max_file_full=3
2026-07-17 10:48:54: Client with id=3 has 0 incremental file backups max_file_incr=40
2026-07-17 10:48:54: Client with id=1 has 1 full file backups max_file_full=3
2026-07-17 10:48:54: Client with id=1 has 0 incremental file backups max_file_incr=40
2026-07-17 10:48:54: Client with id=2 has 1 full file backups max_file_full=3
2026-07-17 10:48:54: Client with id=2 has 0 incremental file backups max_file_incr=40
2026-07-17 10:48:54: Client with id=4 has 1 full file backups max_file_full=3
2026-07-17 10:48:54: Client with id=4 has 0 incremental file backups max_file_incr=40
2026-07-17 10:48:54: Client with id=5 has 1 full file backups max_file_full=3
2026-07-17 10:48:54: Client with id=5 has 0 incremental file backups max_file_incr=40
2026-07-17 10:48:54: Deleting old logs...
2026-07-17 10:48:54: Done deleting old logs
2026-07-17 10:48:54: Cleaning history...
2026-07-17 10:48:54: Rewriting daily history...
2026-07-17 10:48:54: Reading history...
2026-07-17 10:48:54: 278 history items read
2026-07-17 10:48:54: Deleting history...
2026-07-17 10:48:54: Writing history...
2026-07-17 10:48:54: Rewriting monthly history...
2026-07-17 10:48:54: Reading history...
2026-07-17 10:48:54: 12 history items read
2026-07-17 10:48:54: Deleting history...
2026-07-17 10:48:54: Writing history...
2026-07-17 10:48:54: Rewriting yearly history...
2026-07-17 10:48:54: Reading history...
2026-07-17 10:48:54: 0 history items read
2026-07-17 10:48:54: Deleting history...
2026-07-17 10:48:54: Writing history...
2026-07-17 10:48:54: Done cleaning history
2026-07-17 10:48:54: Cleaning deleted backups history...
2026-07-17 10:48:54: Done cleaning deleted backups history.
2026-07-17 10:48:54: Cleaning up client lists...
2026-07-17 10:48:54: Done cleaning up client lists.
2026-07-17 10:48:54: Cleaning up old client access tokens...
2026-07-17 10:48:54: Done cleaning up old client access tokens.
2026-07-17 10:48:54: Updating statistics...
2026-07-17 10:48:54: Updating image stats...
2026-07-17 10:48:54: Updating file statistics...
2026-07-17 10:48:54: Done updating statistics.
2026-07-17 10:48:54: Free space: 0 bytes
2026-07-17 10:48:55: ERROR: Cleanup failed. Could not remove backups. Please lower the minimal number of backups
2026-07-17 10:48:55: ERROR: Error cleaning up.
So I’m now at a loss. I can’t clean up, I can’t run any new backups and I’m stuck in my current situation with no immediate way out I can find other than to trash the whole thing and start again… but destroying and recreating my setup on a monthly basis in order to keep backing up seems somewhat pointless.
Currently my retention is really conservative too;
File incremental maximum: 40
File incremental minimum: 5
File full maximum: 3
File full minimum: 1
Image incremental max: 5
Image incremental min: 1
Image full max: 2
Image full min: 1
Cleanup window runs from 1am to 7am daily and backup window is from 6pm to midnight daily.
Please help. I love this tool but if I can’t rely on these backups for more than a couple of weeks after a fresh install, it’s useless to me.