This was a system that generally stayed on 24/7, so I am not sure what updates might have caused this to happen. The last update before the system rebooted occurred at "Start-Date: 2018-03-31 09:57:33", see attached update history file.
I should also add that I have been using lightdm along with LXDE on this system. When the error originally occurred, another failure message was "lightdm: PAM unable to dlopen(pam_kwallet.so): /lib/security/pam_kwallet.so: cannot open shared object file: No such file or directory" so I then proceeded to install libpam-kwallet4 and libpam-kwallet5 (as you can see in the install history), which made that error go away, but the lightdm startup problem persisted. I then attempted to install and use gdm, but it failed as well. I then tried lxdm and it succeeded, except that there were many applications that could not be launched once logged into the environment. I believe the problem has something to do with lightdm and gdm not being able to unlock a keyring of some sort, but I don't see libpam-kwallet4 or libpam-kwallet5 mentioned as dependency for it. ** Attachment added: "history.log" https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1760371/+attachment/5097642/+files/history.log -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1760371 Title: Light Display Manager fails to start To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1760371/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs
