I guess problem with starting up lightdm after plymouth is in misconfiguration.
$ cat /etc/init/lightdm.conf ... SKIPPED ... script if [ -n "$UPSTART_EVENTS" ] then [ ! -f /etc/X11/default-display-manager -o "$(cat /etc/X11/default-display-manager 2>/dev/null)" = "/usr/bin/lightdm" -o "$(cat /etc/X11/default-display-manager 2>/dev/null)" = "/usr/sbin/lightdm" ] || { stop; exit 0; } if [ "$RUNLEVEL" = S -o "$RUNLEVEL" = 1 ] then # Single-user mode plymouth quit || : exit 0 fi fi exec lightdm end script ... SKIPPED ... It checks if there is "/usr/bin/lightdm" or "/usr/sbin/lightdm" in /etc/X11/default-display-manager, but in my case it's "lightdm" in that file: $ cat /etc/X11/default-display-manager lightdm -- You received this bug notification because you are a member of Desktop Packages, which is subscribed to lightdm in Ubuntu. https://bugs.launchpad.net/bugs/828576 Title: Light-DM not used after upgrade 11.04→11.10 Status in “lightdm” package in Ubuntu: Triaged Bug description: After the restart step of an upgrade →11.10 LightDM was not used, but GDM still continues to be used. To manage notifications about this bug go to: https://bugs.launchpad.net/ubuntu/+source/lightdm/+bug/828576/+subscriptions -- Mailing list: https://launchpad.net/~desktop-packages Post to : desktop-packages@lists.launchpad.net Unsubscribe : https://launchpad.net/~desktop-packages More help : https://help.launchpad.net/ListHelp