These commands are only available when the 'Deleted files' app (files_trashbin) is enabled. These commands are not available in single-user (maintenance) mode.
 trashbin:cleanup   Remove deleted files
 trashbin:expire    Expires the users trash bin

The trashbin:cleanup command removes the deleted files of the specified users in a space-delimited list, or all users if none are specified. This example removes all the deleted files of all users:

sudo -u www-data php occ trashbin:cleanup
Remove all deleted files
Remove deleted files for users on backend Database

This example removes the deleted files of users molly and freda:

sudo -u www-data php occ trashbin:cleanup molly freda
Remove deleted files of   molly
Remove deleted files of   freda

trashbin:expire deletes only expired files according to the trashbin_retention_obligation setting in config.php (see the "Deleted Files" section documentation). The default is to delete expired files for all users, or you may list users in a space-delimited list.