After upgrading cups on my CentOS 6 systems from version 1.4.2-72.el6 to 1.4.2-77.el6, I am no longer able to create working printers, either with lpadmin from the command line or with system-config-printer. When I try to run lpadmin, I get this simple error: [root at vlsi66 ~]# lpadmin -p newprinter -v lpd://printserver/serverqueue-E -P /path/to/ppd/thing.ppd lpadmin: Unknown [root at vlsi66 ~]# Sometimes, the printer does get created (i.e. it shows up in the output of ‘lpstat –a’ and printers.conf gets updated), but sometimes it doesn’t. If the printer does get created, then there is no new ppd in /etc/cups/ppd. If I try to create the printer using system-config-printer, I get an error of CUPS server error (adding printer newprinter) There was an error during the CUPS operation: ‘server-error-service-unavailable’. I’ve looked at file and directory permissions, and checked that cupsd is, in fact, running. There is nothing obvious in the logs, except for this, which happens at exactly the time the printer should get created: localhost - - [26/Apr/2017:09:34:01 -0400] "POST /admin/ HTTP/1.1" 401 0 - - This also occurs if I access localhost:631 from a web browser; and everything works fine up to the point of “Add Printer”, and then the web page shows and Error: box with “Unknown” (from the lpadmin command), and the 401 error shows up in the log. I can’t figure out why it would be a 401 (unauthorized), since everything else worked. Has anyone else run into this problem, where you can’t create a new printer? Thanks! --- Mike VanHorn Senior Computer Systems Administrator College of Engineering and Computer Science Wright State University 265 Russ Engineering Center 937-775-5157 michael.vanhorn at wright.edu