How to disable lightdm?

Note that the method described above doesn't work anymore since 15.04 and later, since Upstart was replaced by Systemd. As described here, one can now disable lightdm like this:

16.04 upward

systemctl disable lightdm.service

15.04, 15.10

systemctl disable lightdm

lightdm is started by Upstart, not SysV Init. So update-rc.d doesn't work.

Use

 echo  "manual" | sudo tee -a /etc/init/lightdm.override

If you want to disable lightdm to enable gdm or kdm or any other display manager, enter the following command in the terminal:

sudo dpkg-reconfigure lightdm

Then enter on ok and then select from the list your desired display manager.

The same answer with screenshots is given here: Reset to Default Unity Login