Problem with Login in GUI Mode in Ubuntu - Tips

On Debian based distros, changing runlevels from 2 to 5 generally will not help. You need to setup a login manager e.g. gdm to start at boot time. To do this, install the login manager and then run

$ sudo update-rc.d gdm defaults

$ sudo /etc/init.d/gdm start

GDM is controlled in this case by the symlinks in /etc/rc2.d. To disable it, you would run something like this:

$ sudo mv /etc/rc2.d/S21gdm /etc/rc2.d/D21gdm

The "S" tells the system to run the target script, whereas "D" tells it to disable. The number indicates the level of priority given to the script. The only thing you need to change is the letter. Simply change it back to re-enable the display manager.