[ubuntu] Ubuntu Enterprise Server 16.04 lightdm not starting on boot up.

Code:

 systemctl status lightdm
● lightdm.service - Light Display Manager
   Loaded: loaded (/lib/systemd/system/lightdm.service; enabled; vendor preset: enabled)
   Active: inactive (dead) (Result: exit-code) since Mon 2016-02-22 10:40:23 EST; 6h ago
     Docs: man:lightdm(1)
  Process: 841 ExecStart=/usr/sbin/lightdm (code=exited, status=1/FAILURE)
  Process: 836 ExecStartPre=/bin/sh -c [ "$(basename $(cat /etc/X11/default-display-manager 2>/dev/null))" = "lightdm" ] (code=exite
d, status=0/SUCCESS)
 Main PID: 841 (code=exited, status=1/FAILURE)

Feb 22 10:40:22 linux140 systemd[1]: lightdm.service: Main process exited, code=exited, status=1/FAILURE
Feb 22 10:40:22 linux140 systemd[1]: lightdm.service: Unit entered failed state.
Feb 22 10:40:22 linux140 systemd[1]: lightdm.service: Failed with result 'exit-code'.
Feb 22 10:40:23 linux140 systemd[1]: lightdm.service: Service hold-off time over, scheduling restart.
Feb 22 10:40:23 linux140 systemd[1]: Stopped Light Display Manager.
Feb 22 10:40:23 linux140 systemd[1]: lightdm.service: Start request repeated too quickly.
Feb 22 10:40:23 linux140 systemd[1]: Failed to start Light Display Manager.

Code:

 root@linux140:/var/log/lightdm# cat lightdm.log
 [+0.00s] DEBUG: Logging to /var/log/lightdm/lightdm.log
 [+0.00s] DEBUG: Starting Light Display Manager 1.17.5, UID=0 PID=703
 [+0.00s] DEBUG: Loading configuration dirs from /usr/share/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-disable-log-backup.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-greeter-wrapper.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-guest-wrapper.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-xserver-command.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/60-lightdm-gtk-greeter.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/60-xubuntu.conf
 [+0.00s] DEBUG: Loading configuration dirs from /usr/local/share/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration dirs from /etc/xdg/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf
 [+0.00s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager
 [+0.00s] DEBUG: Registered seat module xlocal
 [+0.00s] DEBUG: Registered seat module xremote
 [+0.00s] DEBUG: Registered seat module unity
 [+0.02s] DEBUG: Monitoring logind for seats
 [+0.02s] DEBUG: New seat added from logind: seat0
 [+0.02s] DEBUG: Seat seat0: Loading properties from config section Seat:*
 [+0.02s] DEBUG: Seat seat0 has property CanMultiSession=no
 [+0.02s] DEBUG: Seat seat0: Starting
 [+0.02s] DEBUG: Seat seat0: Creating greeter session
 [+0.02s] DEBUG: Seat seat0: Creating display server of type x
 [+0.02s] DEBUG: Using VT 7
 [+0.02s] DEBUG: Seat seat0: Starting local X display on VT 7
 [+0.02s] DEBUG: DisplayServer x-0: Logging to /var/log/lightdm/x-0.log
 [+0.02s] DEBUG: DisplayServer x-0: Writing X server authority to /var/run/lightdm/root/:0
 [+0.02s] DEBUG: DisplayServer x-0: Launching X Server
 [+0.02s] DEBUG: Launching process 759: /usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
 [+0.02s] DEBUG: DisplayServer x-0: Waiting for ready signal from X server :0
 [+0.02s] DEBUG: Acquired bus name org.freedesktop.DisplayManager
 [+0.02s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0
 [+0.07s] DEBUG: Loading users from org.freedesktop.Accounts
 [+0.07s] DEBUG: User /org/freedesktop/Accounts/User1000 added
 [+0.53s] DEBUG: Process 759 terminated with signal 6
 [+0.53s] DEBUG: DisplayServer x-0: X server stopped
 [+0.53s] DEBUG: Releasing VT 7
 [+0.53s] DEBUG: DisplayServer x-0: Removing X server authority /var/run/lightdm/root/:0
 [+0.53s] DEBUG: Seat seat0: Display server stopped
 [+0.53s] DEBUG: Seat seat0: Stopping; greeter display server failed to start
 [+0.53s] DEBUG: Seat seat0: Stopping
 [+0.53s] DEBUG: Seat seat0: Stopping session
 [+0.53s] DEBUG: Seat seat0: Session stopped
 [+0.53s] DEBUG: Seat seat0: Stopped
 [+0.53s] DEBUG: Required seat has stopped
 [+0.53s] DEBUG: Stopping display manager
 [+0.53s] DEBUG: Display manager stopped
 [+0.53s] DEBUG: Stopping daemon
 [+0.53s] DEBUG: Seat seat0: Stopping session
 [+0.53s] DEBUG: Exiting with retu value 1
 [+0.00s] DEBUG: Logging to /var/log/lightdm/lightdm.log
 [+0.00s] DEBUG: Starting Light Display Manager 1.17.5, UID=0 PID=793
 [+0.00s] DEBUG: Loading configuration dirs from /usr/share/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-disable-log-backup.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-greeter-wrapper.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-guest-wrapper.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-xserver-command.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/60-lightdm-gtk-greeter.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/60-xubuntu.conf
 [+0.00s] DEBUG: Loading configuration dirs from /usr/local/share/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration dirs from /etc/xdg/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf
 [+0.00s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager
 [+0.00s] DEBUG: Registered seat module xlocal
 [+0.00s] DEBUG: Registered seat module xremote
 [+0.00s] DEBUG: Registered seat module unity
 [+0.00s] DEBUG: Monitoring logind for seats
 [+0.00s] DEBUG: New seat added from logind: seat0
 [+0.00s] DEBUG: Seat seat0: Loading properties from config section Seat:*
 [+0.00s] DEBUG: Seat seat0 has property CanMultiSession=no
 [+0.00s] DEBUG: Seat seat0: Starting
 [+0.00s] DEBUG: Seat seat0: Creating greeter session
 [+0.00s] DEBUG: Seat seat0: Creating display server of type x
 [+0.01s] DEBUG: Using VT 7
 [+0.01s] DEBUG: Seat seat0: Starting local X display on VT 7
 [+0.01s] DEBUG: DisplayServer x-0: Logging to /var/log/lightdm/x-0.log
 [+0.01s] DEBUG: DisplayServer x-0: Writing X server authority to /var/run/lightdm/root/:0
 [+0.01s] DEBUG: DisplayServer x-0: Launching X Server
 [+0.01s] DEBUG: Launching process 801: /usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
 [+0.01s] DEBUG: DisplayServer x-0: Waiting for ready signal from X server :0
 [+0.01s] DEBUG: Acquired bus name org.freedesktop.DisplayManager
 [+0.01s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0
 [+0.01s] DEBUG: Loading users from org.freedesktop.Accounts
 [+0.01s] DEBUG: User /org/freedesktop/Accounts/User1000 added
 [+0.12s] DEBUG: Process 801 terminated with signal 6
 [+0.12s] DEBUG: DisplayServer x-0: X server stopped
 [+0.12s] DEBUG: Releasing VT 7
 [+0.12s] DEBUG: DisplayServer x-0: Removing X server authority /var/run/lightdm/root/:0
 [+0.12s] DEBUG: Seat seat0: Display server stopped
 [+0.12s] DEBUG: Seat seat0: Stopping; greeter display server failed to start
 [+0.12s] DEBUG: Seat seat0: Stopping
 [+0.12s] DEBUG: Seat seat0: Stopping session
 [+0.12s] DEBUG: Seat seat0: Session stopped
 [+0.12s] DEBUG: Seat seat0: Stopped
 [+0.12s] DEBUG: Required seat has stopped
 [+0.12s] DEBUG: Stopping display manager
 [+0.12s] DEBUG: Display manager stopped
 [+0.12s] DEBUG: Stopping daemon
 [+0.12s] DEBUG: Seat seat0: Stopping session
 [+0.12s] DEBUG: Exiting with retu value 1
 [+0.00s] DEBUG: Logging to /var/log/lightdm/lightdm.log
 [+0.00s] DEBUG: Starting Light Display Manager 1.17.5, UID=0 PID=809
 [+0.00s] DEBUG: Loading configuration dirs from /usr/share/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-disable-log-backup.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-greeter-wrapper.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-guest-wrapper.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-xserver-command.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/60-lightdm-gtk-greeter.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/60-xubuntu.conf
 [+0.00s] DEBUG: Loading configuration dirs from /usr/local/share/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration dirs from /etc/xdg/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf
 [+0.00s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager
 [+0.00s] DEBUG: Registered seat module xlocal
 [+0.00s] DEBUG: Registered seat module xremote
 [+0.00s] DEBUG: Registered seat module unity
 [+0.00s] DEBUG: Monitoring logind for seats
 [+0.00s] DEBUG: New seat added from logind: seat0
 [+0.00s] DEBUG: Seat seat0: Loading properties from config section Seat:*
 [+0.00s] DEBUG: Seat seat0 has property CanMultiSession=no
 [+0.00s] DEBUG: Seat seat0: Starting
 [+0.00s] DEBUG: Seat seat0: Creating greeter session
 [+0.00s] DEBUG: Seat seat0: Creating display server of type x
 [+0.01s] DEBUG: Using VT 7
 [+0.01s] DEBUG: Seat seat0: Starting local X display on VT 7
 [+0.01s] DEBUG: DisplayServer x-0: Logging to /var/log/lightdm/x-0.log
 [+0.01s] DEBUG: DisplayServer x-0: Writing X server authority to /var/run/lightdm/root/:0
 [+0.01s] DEBUG: DisplayServer x-0: Launching X Server
 [+0.01s] DEBUG: Launching process 817: /usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
 [+0.01s] DEBUG: DisplayServer x-0: Waiting for ready signal from X server :0
 [+0.01s] DEBUG: Acquired bus name org.freedesktop.DisplayManager
 [+0.01s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0
 [+0.01s] DEBUG: Loading users from org.freedesktop.Accounts
 [+0.01s] DEBUG: User /org/freedesktop/Accounts/User1000 added
 [+0.12s] DEBUG: Process 817 terminated with signal 6
 [+0.12s] DEBUG: DisplayServer x-0: X server stopped
 [+0.12s] DEBUG: Releasing VT 7
 [+0.12s] DEBUG: DisplayServer x-0: Removing X server authority /var/run/lightdm/root/:0
 [+0.12s] DEBUG: Seat seat0: Display server stopped
 [+0.12s] DEBUG: Seat seat0: Stopping; greeter display server failed to start
 [+0.12s] DEBUG: Seat seat0: Stopping
 [+0.12s] DEBUG: Seat seat0: Stopping session
 [+0.12s] DEBUG: Seat seat0: Session stopped
 [+0.12s] DEBUG: Seat seat0: Stopped
 [+0.12s] DEBUG: Required seat has stopped
 [+0.12s] DEBUG: Stopping display manager
 [+0.12s] DEBUG: Display manager stopped
 [+0.12s] DEBUG: Stopping daemon
 [+0.12s] DEBUG: Seat seat0: Stopping session
 [+0.12s] DEBUG: Exiting with retu value 1
 [+0.00s] DEBUG: Logging to /var/log/lightdm/lightdm.log
 [+0.00s] DEBUG: Starting Light Display Manager 1.17.5, UID=0 PID=825
 [+0.00s] DEBUG: Loading configuration dirs from /usr/share/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-disable-log-backup.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-greeter-wrapper.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-guest-wrapper.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-xserver-command.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/60-lightdm-gtk-greeter.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/60-xubuntu.conf
 [+0.00s] DEBUG: Loading configuration dirs from /usr/local/share/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration dirs from /etc/xdg/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf
 [+0.00s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager
 [+0.00s] DEBUG: Registered seat module xlocal
 [+0.00s] DEBUG: Registered seat module xremote
 [+0.00s] DEBUG: Registered seat module unity
 [+0.00s] DEBUG: Monitoring logind for seats
 [+0.00s] DEBUG: New seat added from logind: seat0
 [+0.00s] DEBUG: Seat seat0: Loading properties from config section Seat:*
 [+0.00s] DEBUG: Seat seat0 has property CanMultiSession=no
 [+0.00s] DEBUG: Seat seat0: Starting
 [+0.00s] DEBUG: Seat seat0: Creating greeter session
 [+0.00s] DEBUG: Seat seat0: Creating display server of type x
 [+0.01s] DEBUG: Using VT 7
 [+0.01s] DEBUG: Seat seat0: Starting local X display on VT 7
 [+0.01s] DEBUG: DisplayServer x-0: Logging to /var/log/lightdm/x-0.log
 [+0.01s] DEBUG: DisplayServer x-0: Writing X server authority to /var/run/lightdm/root/:0
 [+0.01s] DEBUG: DisplayServer x-0: Launching X Server
 [+0.01s] DEBUG: Launching process 833: /usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
 [+0.01s] DEBUG: DisplayServer x-0: Waiting for ready signal from X server :0
 [+0.01s] DEBUG: Acquired bus name org.freedesktop.DisplayManager
 [+0.01s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0
 [+0.01s] DEBUG: Loading users from org.freedesktop.Accounts
 [+0.01s] DEBUG: User /org/freedesktop/Accounts/User1000 added
 [+0.12s] DEBUG: Process 833 terminated with signal 6
 [+0.12s] DEBUG: DisplayServer x-0: X server stopped
 [+0.12s] DEBUG: Releasing VT 7
 [+0.12s] DEBUG: DisplayServer x-0: Removing X server authority /var/run/lightdm/root/:0
 [+0.12s] DEBUG: Seat seat0: Display server stopped
 [+0.12s] DEBUG: Seat seat0: Stopping; greeter display server failed to start
 [+0.12s] DEBUG: Seat seat0: Stopping
 [+0.12s] DEBUG: Seat seat0: Stopping session
 [+0.12s] DEBUG: Seat seat0: Session stopped
 [+0.12s] DEBUG: Seat seat0: Stopped
 [+0.12s] DEBUG: Required seat has stopped
 [+0.12s] DEBUG: Stopping display manager
 [+0.12s] DEBUG: Display manager stopped
 [+0.12s] DEBUG: Stopping daemon
 [+0.12s] DEBUG: Seat seat0: Stopping session
 [+0.12s] DEBUG: Exiting with retu value 1
 [+0.00s] DEBUG: Logging to /var/log/lightdm/lightdm.log
 [+0.00s] DEBUG: Starting Light Display Manager 1.17.5, UID=0 PID=841
 [+0.00s] DEBUG: Loading configuration dirs from /usr/share/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-disable-log-backup.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-greeter-wrapper.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-guest-wrapper.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/50-xserver-command.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/60-lightdm-gtk-greeter.conf
 [+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/60-xubuntu.conf
 [+0.00s] DEBUG: Loading configuration dirs from /usr/local/share/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration dirs from /etc/xdg/lightdm/lightdm.conf.d
 [+0.00s] DEBUG: Loading configuration from /etc/lightdm/lightdm.conf
 [+0.00s] DEBUG: Using D-Bus name org.freedesktop.DisplayManager
 [+0.00s] DEBUG: Registered seat module xlocal
 [+0.00s] DEBUG: Registered seat module xremote
 [+0.00s] DEBUG: Registered seat module unity
 [+0.00s] DEBUG: Monitoring logind for seats
 [+0.00s] DEBUG: New seat added from logind: seat0
 [+0.00s] DEBUG: Seat seat0: Loading properties from config section Seat:*
 [+0.00s] DEBUG: Seat seat0 has property CanMultiSession=no
 [+0.00s] DEBUG: Seat seat0: Starting
 [+0.00s] DEBUG: Seat seat0: Creating greeter session
 [+0.00s] DEBUG: Seat seat0: Creating display server of type x
 [+0.01s] DEBUG: Using VT 7
 [+0.01s] DEBUG: Seat seat0: Starting local X display on VT 7
 [+0.01s] DEBUG: DisplayServer x-0: Logging to /var/log/lightdm/x-0.log
 [+0.01s] DEBUG: DisplayServer x-0: Writing X server authority to /var/run/lightdm/root/:0
 [+0.01s] DEBUG: DisplayServer x-0: Launching X Server
 [+0.01s] DEBUG: Launching process 849: /usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
 [+0.01s] DEBUG: DisplayServer x-0: Waiting for ready signal from X server :0
 [+0.01s] DEBUG: Acquired bus name org.freedesktop.DisplayManager
 [+0.01s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0
 [+0.01s] DEBUG: Loading users from org.freedesktop.Accounts
 [+0.01s] DEBUG: User /org/freedesktop/Accounts/User1000 added
 [+0.12s] DEBUG: Process 849 terminated with signal 6
 [+0.12s] DEBUG: DisplayServer x-0: X server stopped
 [+0.12s] DEBUG: Releasing VT 7
 [+0.12s] DEBUG: DisplayServer x-0: Removing X server authority /var/run/lightdm/root/:0
 [+0.12s] DEBUG: Seat seat0: Display server stopped
 [+0.12s] DEBUG: Seat seat0: Stopping; greeter display server failed to start
 [+0.12s] DEBUG: Seat seat0: Stopping
 [+0.12s] DEBUG: Seat seat0: Stopping session
 [+0.12s] DEBUG: Seat seat0: Session stopped
 [+0.12s] DEBUG: Seat seat0: Stopped
 [+0.12s] DEBUG: Required seat has stopped
 [+0.12s] DEBUG: Stopping display manager
 [+0.12s] DEBUG: Display manager stopped
 [+0.12s] DEBUG: Stopping daemon
 [+0.12s] DEBUG: Seat seat0: Stopping session
 [+0.12s] DEBUG: Exiting with retu value 1