With virtualization there is a host machine installed on the hardware. This host emulates hardware for several guests (virtual machines). On such emulated hardware a complete OS install can be done. In the end there will be several machines running on one hardware machine. Some reasons to use this:
- Sharing hardware resources (a gigabit network card is often not fully utilized by one machine)
- Freedom to backup and move complete machines to another host (an image of a machine installed on hardware is often not fully compatible with the new hardware)
These documents are based on KVM (Kernel-based Virtual Machine).