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If you Google the term "hypervisor" you get endless definitions that state a hypervisor is also known as either a virtual machine monitor or a virtual machine manager, and that it is a form of hardware virtualization. But, being brand new to VMs and their concepts, this is a fuzzy definition for me.

So, what is the difference - and/or relationship between - a virtual machine and its hypervisor? Can someone give a concrete example?

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Do see the wikipedia article on hypervisors. There are a couple different types, which may be partly why you are confused. en.wikipedia.org/wiki/Hypervisor –  Zoredache Sep 22 '11 at 21:00
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up vote 7 down vote accepted

The hypervisor is the device or software which runs the virtual machine. It's typically responsible for allocating the resources, providing the interface between the virtual machine (the "guest") and the host system as well as any management software.

So if you're using VMware Workstation to run a Windows 7 virtual machine, VMware Workstation is the hypervisor.

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Why can't they just say that in the reference documentation?!? Thanks! –  pnongrata Sep 22 '11 at 20:51
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They don't want to make it too easy on you, or you won't pay for the support contract. ;) –  Coding Gorilla Sep 22 '11 at 20:52
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This is an extension of existing operating system terminology — one that is one of the several alternatives to the seed/nut metaphor. user programs are controlled by the supervisor program, and in a non-virtual system that's where things stop. With virtualization, the supervisor is, in turn, controlled (or monitored, or managed) by a hypervisor program.

All of these programs are softwares. The virtual machine is the pretense of a machine that the supervisor and user programs experience themselves running on. It looks like hardware from the inside.

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Ironically, and this is off-topic, and if I remember correctly, Latin "super" and Greek "hyper" derive from the same original word and mean the same thing. German "ueber" is another sibling. So "supervisor" and "hypervisor" are actually the same word, except that one is all Latin while the other is half Latin, half Greek. :-) –  Andrew J. Brehm Sep 23 '11 at 17:20
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But in fact, the terminology is all Greek to most of us. –  Daniel R Hicks Jul 8 '12 at 4:07
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