I can confirm this problem. I use LDAP authorization with ccreds and when I don't have local account (/etc/passwd+/etc/shadow) I can't login from screensaver.
The same configuration works great for sudo/gdm/ssh/.... -- xscreensaver won't unlock with complex pam setup https://launchpad.net/bugs/27164 -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
