A hypervisor is hardware virtualization technique that allows more than one guest operating system to run simultaneously on a single host.It is a thin layer between host hardware and operating system mainly used to build virtual machines.That’s why it is also been called as VMM (Virtual Machine Manager).
The guest operating system shares the hardware resources of the host so that each guest system has it’s own operating system , processor, memory and other hardware resources.The main job of the hypervisor is to look after the needs of guest operating system and make sure that the operating system’s running in different guest operating system are not interrupting one another.
Hypervisor Types :
1) Bare metal Hypervisor or Type 1 Hypervisor
2) Hosted Hypervisor or Type 2 hypervisor
1) Bare metal hypervisor or Type 1 hypervisor: They are also known as native hypervisors.These hypervisors installs directly on the host’s hardware .The operating system installed runs right above the hypervisor.It manages the guest operating systems.
Example: Vmware ESX server, Microsoft Hyper-v and citrix xen server
2) Hosted Hypervisor or Type 2 hypervisor: These type of hypervisor’s runs within the host’s operating system environment.So the operating system being the first level here then the hypervisor in the second level and third level being the guest operating system’s running under it.
Example: VMware workstation, Microsoft Virtual PC and Parallels workstation.