I am trying to install and run some CUDA exemples in Ubuntu 12.04. First of all, I downloaded all .run files from http://developer.nvidia.com/cuda-downloads, then followed the instructions at http://developer.nvidia.com/nvidia-gpu-computing-, until I got hung up on the first step:

1. Exit the GUI if you are in a GUI environment by pressing Ctrl-Alt-Backspace. Some distributions require you to press this sequence twice in a row; others have disabled it altogether in favor of a command such as sudo /etc/init.d/gdm stop . Still others require changing the system runlevel using a command such as /sbin/init 3 to exit the GUI.

When I type the command sudo /etc/init.d/gdmstop, it returns: gdm command not found

Can anybody help me exit my GUI in order to continue?

Thank you in advance.