Terminal commands for installing VirtualBox in Debian or Ubuntu based systems.
Use with my Youtube Video: How to Install Latest version of VirtualBox in Ubuntu / Debian

Terminal Commands:

sudo apt install virtualbox

if [ "`grep vboxusers /etc/group|grep $USER`" == "" ]; then sudo usermod -G vboxusers -a $USER ; fi

Extension Pack:

Download the VirtualBox Extension Pack from: https://www.virtualbox.org/wiki/Downloads
Open the Extension Pack via your file manager in order to install it with VirtualBox.