After upgrade 12.04->14.04 lightdm fails to start

[Nils Kassube]

I upgraded this Kubuntu laptop using the command "do-release-upgrade -d" from 12.04 to 14.04. After the reboot, the splash screen did not disappear and lightdm didn't start. Running the command "start lightdm" (as root), I got the error message "start: Job failed to start", which wasn't really helpful. I also tried the command "/etc/init.d/lightdm start" and now there was some more information:

[+0.00s] DEBUG: Logging to /var/log/lightdm/lightdm.log
[+0.00s] DEBUG: Starting Light Display Manager 1.9.13, UID=0 PID=2635
[+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/40-kde-plasma.conf
[+0.00s] DEBUG: Loading configuration from /usr/share/lightdm/lightdm.conf.d/40-lightdm-kde-greeter.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 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: Using Xephyr for X servers
[+0.00s] DEBUG: Registered seat module xlocal
[+0.00s] DEBUG: Registered seat module xremote
[+0.00s] DEBUG: Registered seat module unity
[+0.00s] DEBUG: Registered seat module surfaceflinger
[+0.01s] DEBUG: Adding default seat
[+0.01s] DEBUG: Seat: Starting
[+0.01s] DEBUG: Seat: Creating greeter session
[+0.01s] DEBUG: Seat: Failed to find session configuration lightdm-gtk-greeter
[+0.01s] DEBUG: Seat: Failed to create greeter session
 * Starting X display manager lightdm [ OK ]

Even though there was the "[ OK ]" displayed in the last line, lightdm didn't start. Due to the message "Failed to find session configuration lightdm-gtk-greeter" I supposed that the package lightdm-gtk-greeter was missing. And indeed after I installed that package (+ dependencies), lightdm started.

As this is a test-upgrade I could return to the original 12.04 system. On that partition was a file /etc/lightdm/lightdm.conf from 2012 with this contents:

[SeatDefaults]
greeter-session=lightdm-gtk-greeter
user-session=Lubuntu

Obviously this was a leftover of a previous test with the lubuntu-desktop. While I had uninstalled lightdm and most of the other Lubuntu packages, this configuration file was not removed for some reason. And during the upgrade I was not asked if the config file should be replaced but the file stayed untouched.

ProblemType: Bug
DistroRelease: Ubuntu 14.04
Package: ubuntu-release-upgrader-core 1:0.219
ProcVersionSignature: Ubuntu 3.13.0-19.40-generic 3.13.6
Uname: Linux 3.13.0-19-generic i686
ApportVersion: 2.13.3-0ubuntu1
Architecture: i386
CrashDB: ubuntu
CurrentDesktop: KDE
Date: Wed Mar 26 17:26:05 2014
PackageArchitecture: all
SourcePackage: ubuntu-release-upgrader
Symptom: ubuntu-release-upgrader
UpgradeStatus: Upgraded to trusty on 2014-03-26 (0 days ago)

[Nils Kassube (kassube)]

Further experiments showed that it would be better to remove the stale config file /etc/lightdm/lightdm.conf instead of installing the additional package lightdm-gtk-greeter. Then the much nicer qt version of the login screen is in use and the KDE systemsettings can be used to configure the login screen.

[Harald Sitter (apachelogger)]

I am not sure we can do much about broken config files to be honest.

[Nils Kassube (kassube)]

I think the upgrader could check if lightdm was installed before the upgrade. If it wasn't because kdm was in use, then the stale config file could be removed.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Robert Ancell (robert-ancell)]

Closing assumed fixed.