Everyone is talking about containers and virtual machines. And for good reason. They’re super useful in the land of programming – they let you run your code and have it behave the same way on any machine from your desktop PC to a server in the cloud. Awesome!

And, it doesn’t matter if you’re a new or experienced coder, you will want to understand the difference between containers vs virtual machines.

Besides, as organizations big (e.g. Google, Twitter, etc.) and small increasingly adopt agile DevOps practices and cloud computing becomes more and more popular, virtualization (running your code anywhere you want) is quickly and will become the best practice to accelerate modern software delivery.

So what’s the difference?

Containers virtualize the operating system making it possible to run multiple applications (code and infrastructure) using the host computer’s operating system.

Virtual machines virtualize the hardware system so multiple operating systems can run on the hardware of a single physical computer. 

In this article, we’ll take a look at these two virtualization tools in a little more detail. Let’s start by understanding what containers and virtual machines are.

What are Containers?

Containers are a form of operating system virtualization.

The application code together with the infrastructure required to run the application is packaged in a container.

Infrastructure means the things the app needs to run like a runtime, system tools and or libraries. 

The container then shares the kernel (brains/CPU) of the host operating system.

So why the container analogy? Containers are named so because of how portable the software running in a container is. This combination of the application and the infrastructure within a container makes it possible to deliver software quickly and deploy it on a wide range of computer systems without issues.

A containerized application can run anywhere – from a laptop, a bare metal server, a private cloud, to a public cloud. It can also be moved, modified, or destroyed.

What is Docker?

Docker is the most widely used containerization platform.

It’s an open source project that makes it easy to pack, ship, and run applications in containers. 

Even though containers have been around for a while, Docker has played a big role in their widespread adoption. 

So why has Docker popularized containers?

  • It has simplified their implementation. Docker makes it so much easier for software developers and system administrators to take advantage of containerization to speed up the building and testing of applications.
  • It offers performance advantages developers and businesses can’t ignore. For example, Docker containers are lightweight, fast, and efficient. You can build and deploy a Docker container in seconds. 
  • Docker Hub boasts a rich ecosystem: This is like an app store for Docker images and it offers thousands of ready to use Docker images developers can use.
  • It improves modularity and scalability. You can separate the different functionalities of an application (e.g. the database and the server) into different containers so you can update or scale the components separately as demand dictates. 
  • It comes with some pretty appealing features. Docker has a rich set of features that simplify development and deployment. One such handy feature is simplified version control

Other Container Tools and Platforms

Even though it’s the most popular container platform, Docker is far from being the only container technology.  

Other top container providers include Solaris Containers, BSD jails, and CoreOS’rkt.

The most popular container orchestrator is Google’s Kubernetes. Other container orchestration tools include DC/OS and Docker Swarm

The top cloud service providers also offer containers as a service (CaaS) products as follows: 

  • Google Kubernetes Engine (GKE)
  • Amazon Elastic Container Service (ECS)
  • Microsoft Azure Container Instances (ACI)
  • Azure Kubernetes Service (AKS)
  • IBM Cloud Kubernetes Service

What are Virtual Machines?

Before containers came along and dominated the virtualization space, virtual machines were the go to technology for optimizing computing resources.

Virtual machines are a form of hardware virtualization. They make it possible to run multiple virtual computers on the hardware of a single physical computer. 

A virtual machine is simply a virtual replica of a physical computer complete with a guest operating system. 

Virtual machines run on top of a physical machine or host machine with the help of an abstraction layer referred to as a hypervisor or a virtual machine monitor.

This hypervisor plays the following roles: 

  • It enables the host computer to replicate itself into multiple virtual machines.
  • It makes it possible for multiple operating systems to run in parallel. 
  • It allocates the physical computing resources of the host computer (RAM and CPU etc.) to the virtual machines.  

Popular Virtual Machine Software

Containers vs Virtual Machines:  What’s the Difference?

While both containers and virtual machines are forms of virtualization, they use different architectural approaches.

Containers bundle only the application code and the infrastructure required to run it while virtual machines package an entire hardware system complete with the user space and operating system.

This means that containers share the host operating system kernel while virtual machines have guest operating systems.

Virtual machines also require the use of a hypervisor as an abstraction layer but containers operate without a hypervisor. 

Furthermore, each type of virtualization has its own set of advantages and disadvantages as follows:

Advantages of Containers

  • Composed of only the application and its libraries, containers are incredibly lightweight and fast to deploy. Resources are provisioned in a matter of seconds and the application is delivered to the end user faster. 
  • Containers are the ultimate in portability. They can run on any environment and move among systems that use the host OS type.
  • Scaling according to demand is easier and faster as you can deploy multiple containers on a single server or a VM. 

Disadvantages of Containers

  • Security is a major concern with containers. Because the containers share the kernel of the host operating system, a security threat in one container can compromise the entire system.
  • Large enterprise-scale applications can result in hundreds of containers or more, which can quickly become a challenge to manage effectively.
  • Containers lack operating system flexibility. Containers running on the same computer must use the same operating system as the host computer.

Advantages of Virtual Machines

  • As the first generation virtualization technology, virtual machines have had a lot of time to develop and are now a stable technology.  
  • Virtual machines offer superior security. They don’t share an OS so there’s a strong isolation that limits the spread of malware.
  • VMs also offer a flexibility advantage as different operating systems can run on the same host computer.  

Disadvantages of Virtual Machines

  • Since each virtual machine includes a guest operating system plus the hardware to support the OS, virtual machines are quite heavy in size and resource intensive. They require substantial computing resources such as processing power. 
  • They also take their sweet time to load, as the process involves booting multiple operating systems.
  • Due to the sheer size of VMs and the resources they require, they are not as flexible as containers. Shipping VMs to and from the cloud to traditional data centers isn’t as easy as it’s with containers. 

Benefits of Containers and Virtual Machines 

  • In terms of objectives, both technologies increase the portability of an application. The application becomes a self-contained unit that can run anywhere. 
  • They promote efficient use of computing resources, which keeps hardware and energy costs low. Instead of acquiring new hardware and computing resources, you can maximize the utilization of the available computing power.
  • They improve scalability as each component of an application can be scaled up or down in response to demand. 
  • They simplify the work of system administrators and other IT professionals by centralizing administrative tasks.

When To Use Containers vs. Virtual Machines

Thanks to their versatility and resource efficiency, containers are seeing widespread adoption by SMEs as well as big companies.

But this doesn’t mean Docker will swallow up virtual machines. There are situations where VMs make more sense. 

Taking into account the pros and cons of both containers and virtual machines, have ideal use cases as follows: 

Ideal Use Cases for Containers

  • Containers are the perfect for microservice architectures where each component of the application runs independently from the other components.
  • Containerized applications provide the portability and flexibility multi-cloud deployments require.
  • Containers can speed up the development, testing, and deployment of applications. This makes them compatible with DevOps practices such as continuous integration and continuous deployment (CI/CD)

Uses of Virtual Machines

  • Virtual machines, on the other hand, are ideal for: 
  • Running multiple applications on multiple servers
  • Running applications that require a fully fledged operating system
  • When managing a range of operating systems
  • When you have a wide variety of operating systems to manage
  • VMs also win where security is a top priority. With each VM enjoying hardware level abstraction, it’s not easy for security threats to crash the whole system. 

Recommended Learning Resources for Containers and Virtualization

Hopefully, this beginners guide has helped you understand the basics of containers and virtualization. But there’s a lot more to containerization and virtualization. 

Below are some excellent courses and books to give you a deeper understanding of these practices and technologies and equip yourself with the skills to apply in real life projects.

Docker for the Absolute Beginner 

Designed with beginners in mind, Docker for the Absolute Beginner 

is one of the best courses to learn the basic concepts of Docker.

Easy to understand explanations will help you grasp the concepts fast while demos and coding exercises will ensure the concepts will stick. 

Overall, the course will give you a solid foundation in containerization and prepare you for more advanced learning.

Docker Deep Dive: Zero to Docker in a single book

Docker Deep Dive offers an excellent introduction to Docker.

Written by a Docker Captain, it simplifies Docker and brings it to life with attractive color illustrations. 

In fact, BookAuthority rates it as  “the number 1 all-time best book on Docker”. 

Pluralsight Grow your virtualization skills Course

The Pluralsight Grow Your Virtualization Skills course will equip you with in-demand virtualization skills.

Learn how to use the top virtual machine software like VMware vSphere, Microsoft Hyper-v, Citrix XenDesktop, and other virtualization solutions. 

Virtualization Essentials 

What better way to learn virtualization skills than by building your own virtual machine. Virtualization Essentials takes a hands-on approach to give you a core understanding of virtualization and how it works.

Clear explanations will help you understand the concepts while putting the skills you gain into practice to build your very own virtual machine will equip you with practical skills you can apply in the workplace.

To Wrap Up

Just as the practice of shipping physical containers revolutionized the global logistics industry, the software container is a game changing invention in software development, testing, and deployment.

Understanding contains vs virtual machines and being able to add them to your skills set can make you a more attractive candidate and help you land the role of your dreams. 

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