What’s the Difference Between Containers and Virtual Machines?

Containers and virtual machines are both deployment technologies. In the software development lifecycle, deployment is the mechanism that makes an application run efficiently on a server or device. The application requires several additional software components called dependencies that are closely related to the underlying operating system of the server. All these different software layers between the application code and the physical device are called the application environment.

Challenges in software deployment

Organizations typically have to deploy applications in multiple environments—for example, developing on the Linux environment and testing on Windows—before releasing new features. Moving the application between environments can result in bugs and glitches, which lower productivity, due to missed dependencies. At the same time, building and testing the application in just one environment limits its usefulness. Here are some examples:

• You may have to develop different versions for users with different operating systems
• Your system administrators must update and maintain all environments uniformly, increasing development costs
• You may find it challenging to move your applications from on-premises data centers to the cloud or between different cloud environments

Purpose of virtual machines

Historically, virtual machine technology was developed to efficiently use increasing physical hardware capacity and processing power. Running a single application environment on a single physical server underutilized hardware resources. Virtual machines allow organizations to install multiple operating systems and create multiple environments on the same physical machine.

Purpose of containers

Containers were created to package and run applications in a predictable and repeatable way across multiple environments. Instead of recreating the environment, you packaged the application to run on all types of physical or virtual environments. This is similar to putting an astronaut in a spacesuit instead of recreating the Earth's atmosphere for them on another planet.

Containers virtualize the operating system so the application can run independently on any platform. Virtual machines go beyond that to virtualize physical machines, so you can use your hardware resources efficiently. We give some more differences below.

How they work

Container technology involves building self-sufficient software packages that perform consistently, regardless of the machines they run on. Software developers create and deploy container images—files containing the necessary information to run the application. Container images are read-only and cannot be altered by the computer system.

Virtual machine technology involves installing virtualization software on a physical server or computer. The physical computer is called the host computer and the virtual machine is called the guest. You can configure and update the guest operating system and its applications as necessary without affecting the host operating system.

Core technology

Virtual machines use hypervisors that communicate between the guest operating system and the host operating system. The hypervisor coordinates resource sharing, so the virtual machine runs in isolation alongside several others on the same hardware.

Containers, on the other hand, use a container engine or container runtime. This is software that acts as an intermediary agent between the containers and the operating system, providing and managing system resources that the application needs. Docker is the most popular open-source container engine.

Size

Virtual machine image files are larger in size (several GB) as they contain their own operating system. Increased resources mean you can duplicate, split, abstract, and emulate entire servers, databases, desktops, and networks. Container files are more lightweight, and you can measure them in MB. Containers only package the resources required to run a single application.