Overview
The physical server boots normally. It then runs a program that boots each virtual server within a virtualization environment (similar to an emulator). The virtual servers have no direct access to hardware and are usually booted from a disk image.
There are two kinds of virtualizations: software based and hardware based. In a software based virtualization environment, the virtual machines share the same kernel and actually require the main node’s resources. This kind of virtualization normally has many benefits in a web hosting environment because of quota incrementing and decrementing in real time with no need to restart the node. The main examples are Virtuozzo (a product of swsoft.com), HyperVM (a product of lxlabs.com), Vserver, and OpenVZ which is the core kernel of both virtuozzo and hypervm.