Chapter 1. Introduction

This chapter introduces various virtualization technologies, applications and features and explains how they work. The purpose of this chapter is to assist Red Hat Enterprise Linux users in understanding the basics of virtualization.

1.1. What is virtualization?

Virtualization is a broad computing term for running software, usually operating systems, concurrently and isolated from other programs on one system. Most existing implementations of virtualization use a hypervisor, a software layer that controls hardware and provides guest operating systems with access to underlying hardware. The hypervisor allows multiple operating systems to run on the same physical system by offering virtualized hardware to the guest operating system. There are various methods for virtualizing operating systems:

Hardware-assisted virtualization is the technique used for full virtualization with KVM.
Para-virtualization is a technique used by Xen to run Linux guests.
Software virtualization or emulation. Software virtualization uses binary translation and other emulation techniques to run unmodified operating systems. Software virtualization is significantly slower than hardware-assisted virtualization or para-virtualization. Software virtualization, using QEMU without KVM, is unsupported by Red Hat Enterprise Linux.