How To Disable Linux GUI from boot?

edit the following line in /etc/inittab

id:5:initdefault: and

change it to

id:3:initdefault:

so if  you reboot the default running level is 3 which is not GUI

For Debian 8-9/Jessie-Stretch use the following command:

In order to make text boot the default under systemd (regardless of which distro, really):

systemctl set-default multi-user.target

To change back to booting to the GUI,

systemctl set-default graphical.target