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VM facts & stats

7 fact-checked facts about virtual machines, each with the reason behind it. 5 more are in today's round and join this page after it closes.

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The basics

In virtualization, what is the physical computer that runs virtual machines called?

AnswerThe host

The physical machine is the host; the virtual machines running on it are guests.

What is the name of the software layer that creates and runs virtual machines?

AnswerHypervisor

A hypervisor, also called a virtual machine monitor, allocates hardware resources to virtual machines.

Going deeper

Where does a Type 1 hypervisor run?

AnswerDirectly on the physical hardware

Type 1, or bare-metal, hypervisors run directly on hardware, while Type 2 hypervisors run on a host operating system.

What is nested virtualization?

AnswerRunning a virtual machine inside another virtual machine

Nested virtualization lets a hypervisor run inside a VM, so that guest can host its own virtual machines.

Compared with virtual machines, what do containers typically share?

AnswerThe host operating system's kernel

Containers isolate apps but share the host OS kernel, while each VM runs its own full operating system.

Expert level

What is paravirtualization?

AnswerA guest OS is modified to cooperate with the hypervisor

In paravirtualization the guest OS knows it is virtualized and calls the hypervisor directly, reducing overhead.

In security, what is a 'VM escape'?

AnswerCode in a guest breaking out to affect the host

A VM escape is an exploit where a program inside a virtual machine breaks isolation and interacts with the host.

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