Starting Ubuntu Xubuntu without the GUI

For Ubuntu 11.10 and higher

Edit /etc/default/grub

vi /etc/default/grub

Find out this line:

GRUB_CMDLINE_LINUX_DEFAULT="quiet splash"

Change it to:

GRUB_CMDLINE_LINUX_DEFAULT="text"

Update Grub:

sudo update-grub

Please notice, you do NOT need to remove / disable lightdm upstart conf, it already does that for you.

lightdm.conf

# Check kernel command-line for inhibitors, unless we are being called
        # manually
        for ARG in $(cat /proc/cmdline); do
            if [ "$ARG" = "text" ]; then
                plymouth quit || :
                stop
                exit 0
            fi
        done

You will still be able to use X by typing startx after you logged in.