I have this problem, and found a thread here: https://askubuntu.com/questions/584207/cannot-log-in-at-locked-screensaver-must-log-in-with-switch-user?utm_medium=organic&utm_source=google_rich_qa&utm_campaign=google_rich_qa
The fix that worked for me was a permission problem on /etc/shadow $ ls -l /etc/shadow -rw-r----- 1 root shadow 2202 Jun 23 12:39 /etc/shadow For me the permission was: $ ls -l /etc/shadow -rw-r----- 1 root root 2202 Jun 23 12:39 /etc/shadow When I changed the group to shadow and restarted the system. I was able to login from the lock screen again. The reason I believe that restarting is required is that the lightdm crashes if it cannot access the shadow file. and once it crashed, you get the message about authentication failure, switch to greeter. The explanation was that the lockscreen runs in user context, whereas the greeter runs as root, so the shadow group allows lightdm to access it. I tried the lock screen several times now, and it is solidly working. I did not change the group from shadow to root, so perhaps an update changed the file permission, or a patch changed the password utility. not sure. -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1733557 Title: Login screen showing Authentication Failure Switch to greeter... To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/unity/+bug/1733557/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
