By removing the xorg-x11-server-common package, the system no longer has X Windows
installed. If X Windows is not installed then the system cannot boot into graphical user mode.
This prevents the system from being accidentally or maliciously booted into a graphical.target
mode. To do so, run the following command:
$ sudo apt_get groupremove "X Window System"
$ sudo apt_get remove xorg-x11-server-common