I am trying to make my own Live USB and I have successfully generated an ISO file with a newly installed, configured and customized Xubuntu 12.04 LTS installation.

My problem is that, no matter I boot the ISO in VirtualBox or in GRUB with loopback, it just cannot start the lightdm.

When booting, I can see the log messages on the screen, it stucks at Stopping System V compablities or Configuring Network security. And tty7 is frozen... If I switch to tty1, I can get a logged-in shell as ubuntu@ubuntu.

The weird thing is: When I type sudo start lightdm or just sudo lightdm, it will switch to tty7 and the screen flashes. Then nothing happened. Return to tty1 and I can see lightdm running, process xxxx. But the process does not exist. It was just crashed immediately I think. (That's why the screen flashes.)

However, when I type startx, I can get into the desktop! That's amazing for me. I am not very clear about the relationship between X Server and Display Manager, but I think lightdm is running when I see the desktop!

Then, what's wrong with sudo start lightdm? I use this command every time I power on my laptop since I have a text parameter added in grub.cfg. It never "crashed immediately".

I need to use sudo start lightdm because it gets me into "Xubuntu Session" instead of "Xfce Session", the prior is more beautiful...

Could anyone help?


Well, I figured out why according to /var/log/lightdm/lightdm.log:

DEBUG: Failed to load session file /usr/share/xsessions/ubuntu.desktop
DEBUG: Session 1800: Sending SIGTERM
Started seesion 2020 with service 'lightdm', username 'lightdm'
DEBUG: Session 2020 authentication complete with return value 0: Success
DEBUG: Greeter authorized
DEBUG: Logging to /var/log/lightdm/x-0-greeter.log
DEUBG: Failed to load session file /usr/share/xgreeters/default.desktop: No such file or directory
DEBUG: Greeter failed to start
DEBUG: Stopping display

There was something wrong with /etc/lightdm/lightdm.conf. I changed it to:


This forced it to use xubuntu.desktop and lightdm-gtk-greeter.desktop instead of ubuntu.desktop and default.desktop, which do not exist and will cause failure.

  • You saved my day
    – bjornhol
    Oct 29 '13 at 18:41

had the same issue - you can create a sym link as temporary workaround:

lrwxrwxrwx   1 root root    27 Nov  3 16:38 .desktop -> lightdm-gtk-greeter.desktop
-rw-r--r--   1 root root   187 Aug 30 20:31 lightdm-gtk-greeter.desktop

this will at least allow lightdm to start.


It seems to be an issue with lightdm.

My solution is to reinstall xubuntu-desktop (despite a lot of packages showed not satisfied dependencies the GUI started in the reboot).

Use this command:

sudo apt-get install --reinstall xubuntu-desktop

For me helped following procedure:

At login screen

Press CTRL+ALT+F1 and log in there and run:

sudo chown -R $USER:$USER $HOME

Then press CTRL+ALT+F7 and try to log in

I use KDE, so my /etc/lightdm/lightdm.conf is:


The reason a lot of you are seeing failures to open ".desktop" is because the upgrade leaves lightdm.conf set with "greeter-session=", which means the greeter name is "". Lightdm adds ".desktop" to whatever greeter-session is set to, and tries to open that in /usr/share/xgreeters. Set lightdm.conf correctly, and you don't need to symlink ".desktop".

I found the names of the above files in /usr/share/xgreeters and /usr/share/xsessions, so if your session and greeter choices are different, look in those directories to find out what user-session and greeter-session need to be set to in lightdm.conf.

root@platform:~# ls /usr/share/xsessions/
root@platform:~# ls /usr/share/xgreeters/

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