Virtual Machine - Definition & Overview

What is a Virtual Machine?

A virtual machine (VM) is a software-based simulation of a physical computer that runs its operating system and applications independently. It functions just like a real computer but is hosted within a physical system known as the host machine. VMs are created and managed by a hypervisor, which allocates physical resources like CPU, memory, storage, and networking to each VM. Each VM includes its own virtual hardware, operating system, and data, making it isolated and secure. They are widely used in software development, testing environments, server consolidation, and cloud computing. Their ability to replicate systems, provide sandboxed environments, and improve resource utilization makes them a cornerstone of modern IT infrastructure.

How Does a Virtual Machine Work?

Understanding the workings of virtual machines is key to mastering virtualization. These self-contained environments rely on a systematic process that enables multiple OS instances to run on one device.

Let’s look at the key steps that explain how a virtual machine functions:

1. Physical Host Machine

The physical system is where virtualization takes place. It provides the core hardware components such as processing power (CPU), memory (RAM), storage drives, and network interfaces that are allocated to virtual machines via the hypervisor.

2. Hypervisor Layer

A hypervisor sits between the hardware and the VMs, managing how computing resources are allocated and shared across virtual environments.

3. Virtual Hardware Emulation

The hypervisor creates virtual components like CPU and memory, making each VM function like a standalone machine.

4. Guest Operating System

Each VM runs its own operating system, separate from the host. This allows different OS environments to coexist on the same machine

5. Execution in Isolation

Even though multiple VMs share the same hardware, each one runs in its own space. This means one VM’s problems won’t impact the others, keeping everything stable and secure.

Components of a Virtual Machine

Every virtual machine is built from a set of core components that simulate the functions of a physical computer. Understanding these components helps in configuring environments effectively. Let’s take a closer look at what these components are:

1. Hypervisor

The hypervisor is a software layer that enables virtualization by allocating computing resources and storage to each VM. It creates and runs virtual machines while ensuring they operate independently of one another.

There are two main types of hypervisors:

• Type 1 (Bare-Metal Hypervisor): Installed directly on the physical server, this type of hypervisor interacts directly with the hardware. It offers better performance and is commonly used in enterprise data centers.
• Type 2 (Hosted Hypervisor): Runs on top of an existing operating system. It relies on the host OS to manage hardware resources, making it more suitable for personal or testing environments.

2. Virtual Hardware

Virtual hardware refers to the simulated computing components that are assigned to a virtual machine. The hypervisor is responsible for allocating these resources by abstracting them from the physical hardware of the host system. This process allows the virtual machine to operate in a fully isolated virtual environment, running applications and processes just like a physical computer. Virtual hardware enables efficient resource allocation across multiple VMs, ensuring each one has the components it needs to function independently.

3. Guest Operating System

The guest operating system is the OS installed and running within a virtual machine. It operates independently of the host system and can be any compatible OS, regardless of what the host is using. A single hypervisor can support VMs running diverse operating systems, depending on individual use cases, making virtualization highly flexible for various use cases like development, testing, or legacy application support.

4. Virtual Disk

A virtual disk is a storage file used by a virtual machine to hold its operating system, applications, and data during operation. It functions like a physical hard drive but exists as a file on the host system. Data can be transferred between the virtual disk and the host's storage when needed, typically with controlled access to ensure system stability.

Types of Virtualization

From computing resources to user interfaces, most areas of IT infrastructure can now be virtualized, helping businesses streamline operations.

Below are the five main types of virtualization, each designed to optimize specific areas of the digital ecosystem:

1.  Hardware Virtualization

This involves creating virtual machines that simulate physical computers, all running on a single physical server. A hypervisor manages these VMs by directly interacting with the server’s CPU, memory, and storage. Hardware virtualization improves resource efficiency by allowing different OS environments to operate simultaneously on a single server.

2.  Software Virtualization

Software virtualization allows different operating systems or applications to run on the same physical hardware. For example, running Android on a Windows laptop. It also includes application virtualization, where software is hosted on a central server and accessed remotely by users, it is ideal for remote work, central management, and faster app deployment.

3. Storage Virtualization

This method pools storage from different physical devices and presents it as a unified system. It separates physical hardware from the way data is stored and accessed.

4. Network Virtualization

It is the process of combining physical networking resources into a single virtual network. This allows for the creation of multiple logical networks over shared hardware using software-based management.

5. Desktop Virtualization

It is the process of running a desktop environment on a remote server rather than on a local device. Users access their desktops over a network from any endpoint. This setup is commonly referred to as Virtual Desktop Infrastructure (VDI).

Container vs Virtual Machine: What’s the Difference?

Containers and virtual machines (VMs) both enable isolated environments to run applications on a shared system, but they differ significantly in how they operate.

While virtual machines emulate entire physical hardware systems, including their operating system, containers virtualize only the application layer. A VM runs a full OS instance, managed by a hypervisor, and behaves like a complete computer. In contrast, containers share the host operating system’s kernel and package only the application along with its necessary dependencies (libraries, binaries, etc.).