How do I prevent GDM from running at boot on Ubuntu?

"Just an answer here for anyone using Ubuntu 10.10+

Using rcconf or sysv-rc-conf to disable gdm will not stop GDM from running on startup.

That is because 'upstart' (http://upstart.ubuntu.com/getting-started.html) is now being used to manage these services.

To disable GDM absolutely, and prevent it from running ever, do this:

sudo mv /etc/init/gdm.conf ~/gdm.conf

(To restore GDM put the file back in /etc/init)"

Using sysv-rc-conf and telling gdm not to load works here with Jaunty Jackalope.
Using sysv-rc-conf and telling gdm not to load works here with Jaunty Jackalope.

"I've never dwelt into the internal configurations of initd for Ubuntu in particular, but for other linux flavours it's usually in /etc/inittab.

You'll find there, very up the top, a line that defines your default run-level.
Hopefully you'll have some comments to help you decide which one it is. I'll bet it's 3."

"I think this post has a much better solution for modern Ubuntu (10.X):

... booting with the text kernel parameter will also prevent display managers managed by Upstart (e.g. gdm, kdm and lxdm) from being started at boot time.

If you are using Grub2, then in /etc/default/grub replace:

GRUB_CMDLINE_LINUX_DEFAULT=""quiet splash""

with

GRUB_CMDLINE_LINUX_DEFAULT=""quiet splash text""

then run:

sudo update-grub

Remove splash to disable the splash screen and/or quiet to make the boot process verbose. If you wish to create a separate boot option for the text and GUI mode then check out this.

Then, if you want to go graphical after booting up, I guess you can use startx or start gdm"