What is a virtual machine?
AnswerA software-based computer running on physical hardware
A virtual machine is a software emulation of a computer that runs its own operating system on real hardware.
Tech · Facts & stats
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.
The basics
What is a VM snapshot?
AnswerA saved copy of a VM's state at a point in time
Snapshots capture a VM's disk and often memory state so it can be rolled back to that moment.
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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