Hello Linux Geeksters.

As you know, LightDM is default display manager of Ubuntu. It is fast, extensible and has support for multi-desktop. The Linux Mint developers replaced LightDM with MDM, for their latest operating systems: Linux Mint 13, Linux Mint 14 and Linux Mint 15.
In this article I will show you how to install LightDM on Linux Mint 15 Olivia and Linux Mint 14 Nadia.
Update the local reposities:
$ sudo apt-get update
Install LightDM:
$ sudo apt-get install lightdm gnome-settings-daemon indicator-session unity-greeter ubuntu-mono light-themes
During the installation process, you will be asked to choose the default DM, between LightDM and MDM (choose LightDM):
Optional, other tweaks that can be done:
Remove the LightDM white dots:
$ sudo xhost +SI:localuser:lightdm
$ sudo su lightdm -s /bin/bash
$ gsettings set com.canonical.unity-greeter draw-grid false
Get rid of the Ubuntu logo from LightDM:
$ sudo rm /usr/share/unity-greeter/logo.png
Disable guest account from LightDM:
$ sudo sh -c 'echo "allow-guest=false" >> /etc/lightdm/lightdm.conf'
You can also disable the remote login, on LightDM:
$ sudo sh -c 'echo "greeter-show-remote-login=false" >> /etc/lightdm/lightdm.conf'
To go back and set MDM as the default DM again, do, and choose MDM in the configuration screen:
$ sudo dpkg-reconfigure mdm