I want to disable lightdm from autostart.
Currenty, I run
service lightdm disable from terminal, then run
update-rc.d doesnt help
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:
systemctl disable lightdm.service
systemctl disable lightdm
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