Install Virtualbox

Step 1: Setup Apt Repository

Firstly edit /etc/apt/sources.list file and add one of following line according to your distribution to your system.

For Ubuntu 14.10 ("Utopic Unicorn")
deb http://download.virtualbox.org/virtualbox/debian utopic contrib

For Ubuntu 14.04 ("Trusty Tahr")
deb http://download.virtualbox.org/virtualbox/debian trusty contrib

For Ubuntu 12.04 LTS ("Precise Pangolin")
deb http://download.virtualbox.org/virtualbox/debian precise contrib

For Debian 7.0 ("Wheezy")
deb http://download.virtualbox.org/virtualbox/debian wheezy contrib

For Debian 6.0 ("Squeeze") 
deb http://download.virtualbox.org/virtualbox/debian squeeze contrib non-free

Step 2: Setup Oracle public key

After adding required apt repository in your system, download and import the Oracle public key for apt-secure using following commands.

$ wget http://download.virtualbox.org/virtualbox/debian/oracle_vbox.asc
$ sudo apt-key add oracle_vbox.asc

Step 3: Install Oracle VirtualBox

After completing above steps, lets install VirtualBox using following commands. If you have already installed any older version of VirtualBox, Below command will update it automatically.

$ sudo apt-get update
$ sudo apt-get install virtualbox-4.3

Step 4: Start VirtualBox

We can use dashboard shortcuts to start VirtualBox or simply run following command from terminal.

$ virtualbox