UML

Besides running Linux on the native hardware it is possible to build a program that acts just like the hardware but is a simple user program. If you had such a ``virtual hardware program'' you could run Linux inside that program. This ability already exists and is called UML (User Mode Linux) [13].

User mode linux will allow you to build new systems and experiment with changing them or allow you to debug them without having extra hardware. It will also allow you to create a whole network of systems within one computer so you can experiment with things like beowulf clusters without having the hardware available. As processors become more powerful, more memory becomes available, and hard drive space improves it will be possible to have multiple virtual computers running on one real computer. This is not a new idea and was used on the IBM Mainframe computers in the 1960s (the IBM VM operating system).