Apparently, I've had VirtualBox guest utilities installed on my host system which you are generally just supposed to run on the guest. This issue only occurred when the package was updated. After trial and error, I've found that the offending package is virtualbox-guest-x11:amd64 (5.1.34-dfsg-0ubuntu1.16.04.2), none of the other virtualbox-guest packages cause this problem.
** Summary changed: - LightDM and GDM fail to start after systemd update in VirtualBox guest + LightDM and GDM fail to start after update in virtualbox-guest-x11 -- You received this bug notification because you are a member of Ubuntu Touch seeded packages, which is subscribed to lightdm in Ubuntu. https://bugs.launchpad.net/bugs/1760371 Title: LightDM and GDM fail to start after update in virtualbox-guest-x11 Status in lightdm package in Ubuntu: New Bug description: 1) Output of lsb_release -rd: Description: Ubuntu 16.04.4 LTS Release: 16.04 2) Output of apt-cache policy lightdm: lightdm: Installed: 1.18.3-0ubuntu1.1 Candidate: 1.18.3-0ubuntu1.1 Version table: *** 1.18.3-0ubuntu1.1 500 500 http://us.archive.ubuntu.com/ubuntu xenial-updates/main amd64 Packages 500 http://security.ubuntu.com/ubuntu xenial-security/main amd64 Packages 100 /var/lib/dpkg/status 1.18.1-0ubuntu1 500 500 http://us.archive.ubuntu.com/ubuntu xenial/main amd64 Packages 3) What I expected to happen: - Expected the display manager to take me to the lightdm user login screen. 4) What happened instead: - lightdm made 5 attempts to start before failing. Failure messages were "failed to start Detect the available GPUs and deal with any system changes" and "Failed to start Light Display Manager". ProblemType: Bug DistroRelease: Ubuntu 16.04 Package: lightdm 1.18.3-0ubuntu1.1 ProcVersionSignature: Ubuntu 4.4.0-116.140-generic 4.4.98 Uname: Linux 4.4.0-116-generic x86_64 NonfreeKernelModules: zfs zunicode zcommon znvpair zavl wl ApportVersion: 2.20.1-0ubuntu2.15 Architecture: amd64 Date: Sat Mar 31 17:43:08 2018 InstallationDate: Installed on 2015-11-23 (859 days ago) InstallationMedia: ProcEnviron: TERM=linux PATH=(custom, no user) XDG_RUNTIME_DIR=<set> LANG=en_US.UTF-8 SHELL=/bin/zsh SourcePackage: lightdm UpgradeStatus: Upgraded to xenial on 2017-01-18 (437 days ago) To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/1760371/+subscriptions -- Mailing list: https://launchpad.net/~touch-packages Post to : touch-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~touch-packages More help : https://help.launchpad.net/ListHelp
