sudo apt-get install -y dkms linux-headers-generic
wget -q http://download.virtualbox.org/virtualbox/debian/oracle_vbox.asc -O- | sudo apt-key add –
For Ubuntu 14.04
sudo sh -c 'echo "deb http://download.virtualbox.org/virtualbox/debian trusty contrib" >> /etc/apt/sources.list.d/virtualbox.list'
For Ubuntu 13.10
sudo sh -c 'echo "deb http://download.virtualbox.org/virtualbox/debian saucy contrib" >> /etc/apt/sources.list.d/virtualbox.list'
For Ubuntu 13.04
sudo sh -c 'echo "deb http://download.virtualbox.org/virtualbox/debian raring contrib" >> /etc/apt/sources.list.d/virtualbox.list'
For Ubuntu 12.10
sudo sh -c 'echo "deb http://download.virtualbox.org/virtualbox/debian quantal contrib" >> /etc/apt/sources.list.d/virtualbox.list'
For Ubuntu 12.04
sudo sh -c 'echo "deb http://download.virtualbox.org/virtualbox/debian precise contrib" >> /etc/apt/sources.list.d/virtualbox.list'
For Ubuntu 11.10
sudo sh -c 'echo "deb http://download.virtualbox.org/virtualbox/debian oneiric contrib" >> /etc/apt/sources.list.d/virtualbox.list'
For Ubuntu 11.04
sudo sh -c 'echo "deb http://download.virtualbox.org/virtualbox/debian natty contrib" >> /etc/apt/sources.list.d/virtualbox.list'
Once you added the repo using the above command, Update your repository.
sudo apt-get update && sudo apt-get install -y virtualbox-4.3
http://www.howopensource.com/2013/04/install-virtualbox-ubuntu-ppa/