LightDM is running but does not display on login

LightDM is installed and running by default as a part of the Beta release. Yet, LightDM is not displayed at login time, rather a primitive, GDM like manager is the one we find at login time.

I tried the command sudo dpkg-reconfigure lightdm

which gave the result :

dpkg-maintscript-helper: warning: environment variable DPKG_MAINTSCRIPT_NAME missing dpkg-maintscript-helper: warning: environment variable DPKG_MAINTSCRIPT_PACKAGE missing

while,

sudo stop gdm gives stop: Unknown job: gdm (as GDM is not installed in the Beta Release)

sudo start lightdm gives start: Job is already running: lightdm

So now, how do we make LightDM appear at login time?

Run the following in a terminal:

sudo apt-get update && sudo apt-get install lightdm

That should resolve your issue.

There is a bug for this issue.
If lightdm starts sucessfully on your machine, the workaround is to manually set absolute path to lightdm in the /etc/X11/default-display-manager file:

sudo su
echo "/usr/sbin/lightdm" > /etc/X11/default-display-manager
exit

(when I experienced this problem on my installation, there was only the binary name lightdm in the file.)