I believe I have the same issue, I have package cups 1.6.2-1ubuntu5. When I try and do any admin task via the web interface, I get:
E [15/Sep/2013:18:51:03 +0800] [Client 11] Unknown MD5 username "rob" In my cupsd.conf file, I have the following (relevant bits only): DefaultAuthType BasicDigest (this machine is visible on a domestic LAN only) Require user @lpadmin (in various locations that previously had "require user @SYSTEM") I've tried the workarounds mentioned above, but these have not fixed the problem for me. In /var/log/kern.log, I'm seeing lots of the following: Sep 15 18:50:25 robs-computer kernel: [ 3865.265435] type=1400 audit(1379242225.411:40): apparmor="STATUS" operation="profile_replace" name="/usr/lib/cups/backend/cups-pdf" pid=18814 comm="apparmor_parser" Sep 15 18:50:25 robs-computer kernel: [ 3865.265732] type=1400 audit(1379242225.411:41): apparmor="STATUS" operation="profile_replace" name="/usr/sbin/cupsd" pid=18814 comm="apparmor_parser" -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to cups in Ubuntu. https://bugs.launchpad.net/bugs/1157318 Title: Login error in CUPS when adding a printer (or other admin procedure) Status in “cups” package in Ubuntu: Fix Released Bug description: Using Raring (13.04): When you go to http://localhost:631 to do admin tasks in cups, and enter your login details, the system keep asking the user/password in a loop. In the cups log: E [19/Mar/2013:18:20:10 +0100] [Client 17] pam_authenticate() returned 4 (System error) E [19/Mar/2013:18:20:42 +0100] [Client 16] pam_authenticate() returned 4 (System error) E [19/Mar/2013:18:20:49 +0100] [Client 15] pam_authenticate() returned 4 (System error) In the auth log no info. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/cups/+bug/1157318/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp
