How do I disable GDM and Graphical User Selection?

In Ubuntu 10.04 you should refer to documentation for Upstart which handles starting of tasks and services during boot, stopping them during shutdown and supervising them while the system is running.

Upstart handle start of gdm, so you should edit /etc/init/gdm.conf

sudo vi /etc/init/gdm.conf    # or use nano if vi is unfamiliar

Default runlevel in ubuntu 10.04 is 2 so you must change this line

stop on runlevel [016]

adding "2" in the runlevel list

stop on runlevel [0126]

Now you can reboot the system.

Do:

sudo dpkg-divert  --rename --add /etc/init/gdm.conf

Which prints:

Adding `local diversion of /etc/init/gdm.conf to /etc/init/gdm.conf.distrib'

This will allow you to disable GDM while preventing package upgrades from putting the file back in place and allowing the GDM package to upgrade the configuration file.

In the case of 11.x and above lightdm is used instead of GDM. I instead used the command:

sudo dpkg-divert --rename --add /etc/init/lightdm.conf

To undo it replace the rename and add with a remove.

Recent versions of Ubuntu are using upstart instead of SysV init.

Rename /etc/init/gdm.conf to /etc/init/gdm.disabled.

For Kubuntu, rename /etc/init/kdm.conf to /etc/init/kdm.disabled.