Introduction to Virtualization

Definition of Virtualization

Virtualization is a set of techniques that allow creating one or more “virtual” computers within a real computer. A virtual machine (VM) can be defined as a software implementation of a physical machine, that is, a “software” computer that behaves practically the same as a real computer.

Host OS

It is the OS of the real machine. The host runs the virtualization application that allows creating VMs.

Guest OS

It is the OS of the virtual machine. This guest can run virtualization add-ons to improve integration with the host.

Hypervisor

It is the platform that allows applying virtualization techniques and using different VMs on the same real machine.

Most Known Hypervisors

VMware
VirtualBox
Hyper-V
Parallels (for smaller OS)
QEMU

Utility of Virtualization

Allows testing SW without installing it on the real machine
Allows testing new OS without formatting the real machine
Protection against malware during testing
Run programs not compatible with modern OS
“Duplicable”, “freezable” and recoverable system
Ideal for educational environments

Practical Aspects

Hardware Considerations

Memory is usually the most limiting resource
Virtualization is supported by hardware in modern processors
- Intel: VT-x
- AMD: AMD-V
BIOS/UEFI configuration required to enable these features

Types of Hypervisors

Type 1 (Native)

Runs directly on hardware

Advantages:

Better performance

Examples:

VMware ESXi
Citrix XenServer
Hyper-V

Type 2 (Hosted)

Runs on the host OS

Advantages:

Greater flexibility
Support for different architectures

Examples:

VMware Player
VirtualBox
QEMU

Hypervisor-Types

Paravirtualization

Paravirtualization is a technique that seeks to increase performance by modifying the OS kernel to be aware that it is being virtualized.

Advantages

Better performance than full virtualization
Lighter hypervisor
More efficient communication between systems