VirtualBox is an open-source cross platforms virtualization application that allows anyone to create a
virtual machine on their computer. It is similar to the popular VMware, but much smaller in size and
handles the virtual machine more efficiently.
Installing VirtualBox
To install Virtualbox in Ubuntu 9.10 Karmic Koala, issue this command from a terminal window:
$ sudo apt-get install virtualbox-ose
And that’s it! The apt-get utility will download Virtualbox and its dependencies
VirtualBox 3.1: Beginner's Guide