Samba must use its own spool directory (it is set by a line similar to path = /var/spool/samba, in the [printers] or [printername] section of smb.conf). Samba receives the job in its own spool space and passes it into the spool directory of CUPS (the CUPS spool directory is set by the RequestRoot directive in a line that defaults to RequestRoot /var/spool/cups ). CUPS checks the access rights of its spool directory and resets it to healthy values with every restart. We have seen quite a few people who used a common spooling space for Samba and CUPS, and struggled for weeks with this “problem.”

A Windows user authenticates only to Samba (by whatever means is configured). If Samba runs on the same host as CUPS, you only need to allow “localhost” to print. If it runs on different machines, you need to make sure the Samba host gets access to printing on CUPS.