Public bug reported: A few months back I had the same problem, then I installed lightdm and ran it and since then bug was gone. But 2 days back I got the same bug, I tried running lightdm again, so to stop it I ran sudo stop lightdm but it gives out the message "unable to connect to upstart" and ends.
ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: lightdm 1.18.3-0ubuntu1.1 ProcVersionSignature: Ubuntu 4.4.0-141.167-generic 4.4.162 Uname: Linux 4.4.0-141-generic x86_64 ApportVersion: 2.20.1-0ubuntu2.18 Architecture: amd64 CurrentDesktop: Unity Date: Thu Feb 7 09:42:53 2019 DistributionChannelDescriptor: # This is a distribution channel descriptor # For more information see http://wiki.ubuntu.com/DistributionChannelDescriptor canonical-oem-somerville-xenial-amd64-20160624-2 InstallationDate: Installed on 2018-06-07 (244 days ago) InstallationMedia: Ubuntu 16.04 "Xenial" - Build amd64 LIVE Binary 20160624-10:47 SourcePackage: lightdm UpgradeStatus: No upgrade log present (probably fresh install) ** Affects: lightdm (Ubuntu) Importance: Undecided Status: New ** Tags: amd64 apport-bug xenial -- You received this bug notification because you are a member of Ubuntu Bugs, which is subscribed to Ubuntu. https://bugs.launchpad.net/bugs/1814992 Title: Getting "Authentication Failed" and "Switch to greeter" message on login screen To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1814992/+subscriptions -- ubuntu-bugs mailing list ubuntu-bugs@lists.ubuntu.com https://lists.ubuntu.com/mailman/listinfo/ubuntu-bugs