Ubuntu/Debian Graphical Interface

Some use cases do not require a desktop environment. You can change the default boot target to multi-user.target. After the next reboot, the system will boot to command-line mode and will not start the graphical interface automatically:

sudo systemctl set-default multi-user.target
sudo reboot

To restore graphical startup by default, run:

sudo systemctl set-default graphical.target
sudo reboot