I want to disable lightdm from autostart.
Currenty, I run
service lightdm disable from terminal, then run
update-rc.d doesnt help
lightdm is starter by Upstart, not SysV Init, so update-rc.d doesn't work.
If you want to disable lightdm to enable gdm or kdm or any other display manager, enter the following command in the terminal
Then enter on
The same answer with screenshots is given here: http://askubuntu.com/a/138569/62483