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I did the HWE upgrade and that worked fine. System started fine. But I ran Ubuntu Tweak and it reported massive amounts of cruft. So I did the Janitor and uh-oh...system boots to command line terminal. After research I figured out that lightdm was not starting and got the desktop back by installing and switching to gdm. I'd like to understand the problem and get lightdm back but a day of effort has not rewarded me with success.

I am running this system as a headless box, it has no proprietary drivers.

My goal is to regain lightdm, can anyone suggest an approach?

Here is my lightdm log:

[+0.00s] DEBUG: Logging to /var/log/lightdm/lightdm.log
[+0.00s] DEBUG: Starting Light Display Manager 1.2.3, UID=0 PID=1744
[+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: Adding default seat
[+0.00s] DEBUG: Starting seat
[+0.00s] DEBUG: Starting new display for automatic login as user bill
[+0.00s] DEBUG: Starting local X display
[+0.00s] DEBUG: Using VT 7
[+0.00s] DEBUG: Activating VT 7
[+0.10s] DEBUG: Logging to /var/log/lightdm/x-0.log
[+0.11s] DEBUG: Writing X server authority to /var/run/lightdm/root/:0
[+0.11s] DEBUG: Launching X Server
[+0.11s] DEBUG: Launching process 1749: /usr/bin/X :0 -auth /var/run/lightdm/root/:0 -nolisten tcp vt7 -novtswitch
[+0.11s] DEBUG: Waiting for ready signal from X server :0
[+0.12s] DEBUG: Acquired bus name org.freedesktop.DisplayManager
[+0.12s] DEBUG: Registering seat with bus path /org/freedesktop/DisplayManager/Seat0
[+0.12s] DEBUG: Process 1749 exited with return value 1
[+0.12s] DEBUG: X server stopped
[+0.12s] DEBUG: Removing X server authority /var/run/lightdm/root/:0
[+0.12s] DEBUG: Releasing VT 7
[+0.12s] DEBUG: Display server stopped
[+0.12s] DEBUG: Stopping display
[+0.12s] DEBUG: Display stopped
[+0.12s] DEBUG: Stopping X local seat, failed to start a display
[+0.12s] DEBUG: Stopping seat
[+[+1057.81s] DEBUG: Got signal 15 from process 1
[+1057.81s] DEBUG: Caught Terminated signal, shutting down
[+1057.81s] DEBUG: Stopping display manager
[+1057.81s] DEBUG: Display manager stopped
[+1057.81s] DEBUG: Stopping daemon
[+1057.82s] DEBUG: Exiting with return value 0
share|improve this question
up vote 2 down vote accepted

Fortunately I had a working system to compare it to. Ubuntu Tweak for some reason deleted a symlink in /etc/X11 and this caused lightdm to fail.

The fix is easy:

cd /etc/X11
sudo ln -s /usr/bin/Xorg X

and Bob's yer uncle.

share|improve this answer
thanks mate, you're answer helped me also. cleaned old kernels and couldn't start ubuntu 14.04.2 – adi Mar 20 '15 at 13:34

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