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What is a virtual machine?

A virtual machine (VM) is a virtual environment that functions as a virtual computer system with its own CPU, memory, network interface, and storage, created on a physical hardware system. Software called a hypervisor separates the machine’s resources from the hardware and distributes them appropriately so they can be used by the VM. 

The physical hardware, equipped with a hypervisor such as Kernel-based Virtual Machine (KVM), is called the host, while the many VMs that use its resources are guests. The hypervisor treats compute resources—like CPU, memory, and storage—as a pool of resources that can easily be relocated between existing guests or to new virtual machines.

VMs are isolated from the rest of the system, and multiple VMs can exist on a single piece of hardware, like a server. They can be moved between host servers depending on demand or to use resources more efficiently.  

The operating system in a VM runs in the same way that an operating system or application normally would on the host hardware, so the user experience with a VM will be similar. 

How do VMs work?

Virtualization technology allows you to share a system with many virtual environments. The hypervisor manages the hardware and separates the physical resources from the virtual environments. Resources are partitioned as needed from the physical environment to the VMs.

When the VM is running and a user or program issues an instruction that requires additional resources from the physical environment, the hypervisor schedules the request to the physical system’s resources so that the virtual machine’s operating system and applications can access the shared pool of physical resources.

Types of hypervisors

There are 2 different types of hypervisors that can be used for virtualization.

Type 1

A type 1 hypervisor is on bare metal. VM resources are scheduled directly to the hardware by the hypervisor. KVM is an example of a type 1 hypervisor. KVM was merged into the Linux® kernel in 2007, so if you’re using a modern version of Linux, you already have access to KVM. 

Type 2

A type 2 hypervisor is hosted. VM resources are scheduled against a host operating system, which is then executed against the hardware. VMware Workstation and Oracle VirtualBox are examples of type 2 hypervisors. 

Why use a VM?  

Server consolidation is a top reason to use VMs. Most operating system and application deployments only use a small amount of the physical resources available when deployed to bare metal. By virtualizing your servers, you can place many virtual servers onto each physical server to improve hardware utilization. 

This keeps you from needing to purchase additional physical resources, as well as reducing the need for power, space, and cooling in the datacenter. VMs enable failover and redundancy that could previously only be achieved through additional hardware.

A VM provides an environment that is isolated from the rest of a system, so whatever is running inside a VM won’t interfere with anything else running on the host hardware.

Because VMs are isolated, they are a good option for testing new applications or setting up a production environment. You can also run a single purpose VM to support a specific process.

Why choose Red Hat?

Red Hat has supported virtualization development for a long time—improving the KVM hypervisor and contributing to KVM and oVirt since both communities were founded. 

The KVM hypervisor is now the core of all major OpenStack® and Linux virtualization distributions, and it's set records for overall performance and for running the largest quantity of well-performing VMs on a single server. 

Red Hat® Virtualization is an open, software-defined platform that virtualizes Linux and Microsoft Windows workloads. Built on Red Hat Enterprise Linux and KVM, it features management tools that virtualize resources, processes, and applications—giving you a stable foundation for a cloud-native and containerized future.

All the ways you can start using virtualization

Red Hat Virtualization logo

This is all you need. Really. Install it on anything—from bare-metal hardware to open source or proprietary systems—and start deploying virtual machines by the dozens or hundreds with a hypervisor that can handle it and a management platform that makes it easy.

Red Hat Hyperconverged Infrastructure logo

Deploy storage and virtualization together, even when resources are limited. Use the same server hardware as both hypervisor and controller, so you have a clustered pool of integrated compute and storage resources.

There's a lot more to do with virtualization