Install VirtualBox on ubuntu

                                    wget –q https://www.virtualbox.org/download/oracle_vbox_2016.asc -O- | sudo apt-key add -
#use codename of your linux version,for my case focal is codename for 
#ubuntu 20.04.1
sudo add-apt-repository "deb http://download.virtualbox.org/virtualbox/debian focal contrib"
#you can check codename of your system using command below
lsb_release -cs
sudo apt update && sudo apt install virtualbox-6.1

                                    # sudo -s -H
# apt-get clean
# rm /var/lib/apt/lists/*
# rm /var/lib/apt/lists/partial/*
# apt-get clean
# apt-get update

                                    $ sudo apt install virtualbox

                                    yum install VirtualBox-6.1