This article explains how to install VirtualBox 6.0, virtual machine software, on Ubuntu 18.04.
# If already installed, uninstall
sudo apt remove --purge virtualbox-6.0 virtualbox-dkms
sudo apt update
sudo apt upgrade
wget -q https://www.virtualbox.org/download/oracle_vbox_2016.asc -O- | sudo apt-key add -
wget -q https://www.virtualbox.org/download/oracle_vbox.asc -O- | sudo apt-key add -
sudo add-apt-repository "deb http://download.virtualbox.org/virtualbox/debian bionic contrib"
sudo apt update
sudo apt install virtualbox-6.0