Linux kernel, Nvidia: Turning off graphics in Ubuntu

"You shouldn't directly delete files from the /etc/rcn.d directories as RageZ has said - you should use the update-rc.d script to manage what starts and what does not.

If you use :

update-rc.d gdm remove

That will stop Ubuntu from attempting to start the Display Manager by default, and should leave you with a nice text prompt.

Using Control+Alt+F1 should work too even if GDM has started already - but sometimes if the drivers are particularly broken, it leaves the graphics card in a state where it can no longer switch modes properly, so removing GDM from the startup is probably a better alternative."

"You can force the system to boot in runlevel 1, which will give you a plain text console.
At that point you can use the other hints to disable gdm so the next full boot will also result in a text console.

In grub press 'e' and edit the kernel line to add 'single' and hit 'b' to boot."