If you are using Raspberry PI as headless machine, you do not need to start the graphical server at all. It is useless when Rasbian is used as server OS and disabling it will free ~40MB of RAM.
To do so, you need to edit the /etc/X11/default-display-manager file using your favorite text editor.
$ sudo vim /etc/X11/default-display-manager
Then comment out the line
#/usr/sbin/lightdm
and add a new one
/bin/false
Save the file and reboot the machine. Voila!
Update
There is a easier way of doing it…
Just run the Rasbian configuration utility
$ sudo raspi-config
In boot option menu choose:
- Enable Boot to Desktop/Scratch and enable Console Text.
- Also check SSH by going in ssh and selecting Enable or disable ssh server.
- After you quit, you’ll be asked to reboot, choose Yes.