> Just wondering would UML be considered Hypervisor? If not what exactly
> is a Hypervisor then?
Actually, it depens on who you ask to :), but IMHO, an hypervisor is the
(usually tiny) piece of software that runs on top the hardware (bare
metal) and manage virtual machines (which run on top the hypervisor)
accesses to physical resources.
I think the definition at Wikipedia is accurate enough:
In the case of UML running on top the host operating system, I think the
right view is that the host operating systems acts as hypervisor,
(although the term is not usually utilized in UML parlance) and UML are
the virtual machines (running as UNIX processes) that run on top the
OS/hypervisor. The main difference regarding other cases it is that an
entire host operating systems is usually heavier than dedicated
hypervisors (ej, mainframe virtualization, Xen, VMware ESX, etc.)
However, this topic is open to discussion... :)