Sunil Thakare :: Open Source Evangelist

Sunil Thakare's blog…

Hypervisor: Future of IT Industry


In traditional virtual computing, only one operating system (OS) is loaded at a time above hardware layer and allow another OS to be loaded as a guest operating system, in general sense of virtual computing. The term Hypervisor refers to Virtual Machine Manager (VMM) in


Traditional OS load

general. Its possible to run multiple parallel operating systems without any  OS loaded on hard ware abstract using hypervisor. The Hypervisor is an abstract layer running directly over the hardware without any operating system loaded and allowing multiple instances of operating systems running parallel e.g. running Linux server for website hosting, running database server on other instance of linux server, one more desktop OS like ubuntu desktop, Microsoft Windows 7 desktop, Windows XP etc. are connected to virtual LAN on single computer and router.

Is there any Open Source Hypervisior:

Yes. Its Xen Hypervisior. Xen Hypervisor (XH) is an abstract layer running directly on hardware allowing multiple instances of OSes. XH currently supports architecture x86, x86_64, Itanium, PowerPC, and ARM processors and operating systems like Linux, NetBSD, FreeBSD, Solaris, Windows, and other common operating systems as guests running on the hypervisor.

The computer running XH contains three parts:

1. Xen Hypervisor running directly on hardware

2. Domain 0, the Privileged Domain (Dom0) – Privileged guest running on the hypervisor with
direct hardware access and guest management responsibilities

3. Multiple DomainU, Unprivileged Domain Guests (DomU) – Unprivileged guests running on
the hypervisor; they have no direct access to hardware (e.g. memory, disk, etc.)

The Xen hypervisor runs directly on the hardware and becomes the interface for all hardware requests such as CPU, I/O, and disk for the guest operating systems. By separating the guests from the hardware, the Xen hypervisor is able to run multiple operating systems securely and independently.

The Domain 0 Guest referred to as Dom0 is launched by the Xen hypervisor during initial system start-up and can run any operating system except Windows.

The Dom0 has unique privileges to access the Xen hypervisor that is not allocated to any other Domain Guests. These privileges allow it to manage all aspects of Domain Guests such as starting, stopping, I/O requests, etc. A system administrator can log into Dom0 and manage the entire computer system.

The Domain Guests referred to as DomUs or unprivileged domains are launched and controlled by the Dom0 and independently operate on the system. These guests are either run with a special modified operating system referred to as paravirtualizion or un-modified operating systems leveraging special virtualization hardware (Intel VT and AMD-V) referred to as hardware virtual machine (HVM). Note – Microsoft Windows requires a HVM Guest environment.

What are the advantages of XH?

  • Testing intranet applications on virtual LAN on single PC.
  • Safe browsing
  • Safe web-server and database server
  • Cloud Computing made easy
  • Full utilization of hardware
  • Cost effective industry standard virtualization – its free under GPL

Hardware (H/W) requirements:

  • Atleast 1 GB RAM (2 GB recommended) 
  • CPU having at-least 1 GHz clock speed
  • good video card
  • 5-10 GB Harddisk space.

Where do I get XH:

  • XH open-source, free, copyleft software distributed under GPL.
  • Download iso file from

Enjoy the world of Hypervisor, its new era in virtual computing.

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