One of the hottest new technologies for servers is virtualization, which allows you to install multiple instances of one or more operating systems on one machine. This is ideal especially for servers with a low average load because, instead of configuring a separate physical box for every single instance of an operating system you need, you just run multiple instances of one or more operating systems on one machine. Unfortunately, it's a jungle out there: there are many different and competing virtualization options. This chapter will provide an overview of the possibilities that virtualization offers. You'll also learn how to set up Ubuntu Server for virtualization.