What is a virtual machine?

Key takeaways:

• Virtual machines allow multiple operating systems and applications to run on a single computer, providing flexibility and isolation.

• They offer cost savings, scalability, and easy disaster recovery but can impact performance and memory management when overused.

• Virtual machines are widely used in cloud platforms to host applications, enabling developers to deploy and share their work with ease.

A virtual machine is an emulated environment running on a machine with CPU, memory, and storage. With the help of a virtual machine, we can run additional operating systems on top of the current operating system. For example, we want to run Ubuntu in a Windows environment. A virtual machine is wholly isolated from the host machine and operates as a completely independent entity. There are two types of virtual machines:

1. System virtual machine: It is used to emulate the entire operating system, which simulates an entire physical computer, such as running a Ubuntu operating system in a virtual machine.

2. Process virtual machine: It emulates a process independent of the host environment. This means we run a single application in the virtual environment instead of a whole operating system.

Layers in a virtual machine

A virtual machine’s environment can be broken down into 5 different layers, as shown in the diagram below:

Below, we can see a brief explanation of the different layers of a virtual machine:

1. Infrastructure

The infrastructure consists of the host hardware and the host operating system. The host hardware is the computer or server on which all hypervisors run. Its job is to provide the hardware resources required to run the virtual machines. The host operating system runs directly on the host hardware, manages the hypervisor, and allocates hardware resources.

2. Hypervisor

A hypervisor acts as a bridge between the virtualized OS and the hardware. It pools the hardware resources and allocates them to the host and the guest. Some of the components that a hypervisor needs to do its job are a memory manager, process scheduler, I/O stack, device drivers, security manager, and network stack.

3. Virtual machine

The virtual machines use the resources allocated to them by the hypervisor to run a guest operating system and applications on top of that operating system.

4. Operating system

This is referred to as the guest operating system running in the environment created by the virtual machine; its job is to run applications that a user may want to run in a virtual environment.

5. Applications

These are the various applications we may want to run on a virtual environment emulated by a virtual machine, such as an application running on an Ubuntu operating system in a virtual machine.

Advantages and disadvantages

Virtual machines are easy to manage and maintain, offering several advantages over physical machines. However, they also have some potential disadvantages.

Container vs. virtual machine

In virtual machines, the hypervisors start by dividing the host’s underlying hardware among the different virtual machines running on the host so they can run their own operating system and applications. However, in containers, the operating system of the host machine is virtualized to run applications so a container only contains the application and its dependencies but not an entire operating system.

Learn more about the differences between containers and virtual machines.

Virtual machine on the cloud

As time passes, we see a rise in cloud computing platforms to serve the computing industry; these providers use virtual machines for their users on top of their own servers to serve the users’ requests and host their applications.

If a web developer just finished writing a web application and now needs to showcase it to the world so they can access it, he would need some way to publish it onto the internet. He can sign up with a cloud service provider, who would allocate a virtual machine for the developer, on top of which the web application can be hosted. Now, anyone can access the website using the address of the virtual machine on which the application is hosted.

To learn more about the cloud virtual machine, look into our Answer: What is a cloud virtual machine?

Test yourself

Before moving on to the conclusion, test your understanding.

Conclusion

Virtual machines are powerful tools that let us run multiple operating systems and applications on a single computer. They provide flexibility, cost savings, and easy disaster recovery, making them useful for personal and professional use. However, they can be resource-heavy and may slow down performance if too many are running on one system.

In today’s world, virtual machines are widely used in cloud computing to host applications and services. Understanding how they work and their benefits can help us use them effectively, whether for developing software or deploying web applications.