Breaking Down Docker Containers vs. Virtual Machines

June 21, 2021

Containers and virtual machines (VMs) help maximize the value that you get from the available software resources and computer hardware. Virtual machines are historically popular for their ability to allow users to run multiple operating systems simultaneously, as well as utilize the same hardware resources.

Virtual machines depend heavily on a hypervisor. It allows a single host computer to support several guest virtual machines. This is made possible through the sharing of different resources including processing power and memory.

Containers, on the other hand, enhance visualization and overall efficiency. This is because they eliminate the need for hypervisors and multiple virtual machines.

Nevertheless, containers and virtual machines are still similar in several ways. This includes their ability to improve IT efficiency, as well as enhance the software development lifecycle. The two technologies also support application portability which simplifies the work for DevOps engineers.


This article discusses how virtual machines and containers work, as well as their pros and cons. It also guides you on which technology to choose depending on your resources and needs.

How VMs work

Virtual machines operate using virtualization technology. This computing technology stimulates virtual hardware to create versions of computer resources which include servers and operating system environments. These resources then allow multiple virtual machines to run on a single computer system. This way, users can optimize the usage of their computer hardware resources.

In such an arrangement, the physical machine is referred to as the host and the VMs the guests. A hypervisor manages these processes and provides resources such as storage and memory from the host computer to guests.

Since VMs use the same hardware resources, their operations might overrun each other. Thankfully, the hypervisor schedules such procedures to avoid such cases. Therefore, the presence of a hypervisor is a mandatory condition for virtual machines to work. It virtualizes and distributes host resources.

How containers work

Containers are packages of software that include everything that the software needs to run, be it code, binaries, libraries, or dependencies. Docker Swarm and Kubernetes are two powerful container orchestration frameworks.

Components in a container are preserved on a code-based file known as the image. The file includes all dependencies and libraries. The image consists of configuration files and RPM packages. Containers are so small and are loosely coupled together in the hundreds. As such, you need Kubernetes, OpenShift, or other container orchestration platforms to manage and provision them.

Containers pros

  • A hardware hypervisor is not a requirement for containers to run because their processes are isolated from one another. This makes containers much smaller than VMs. Containers also require fewer resources.
  • Containers are fast. It takes only a few milliseconds to boot a Docker container from its image. For a virtual machine, you’ll have to wait for at least a few minutes for it to boot and be ready for use.
  • DevOps engineers and other teams can also share containers. This is important since it ensures application portability during development.

Containers cons

  • Containers lack a robust security infrastructure. Compared to VMs, containers have a weaker security boundary. This is due to the lightweight isolation that containers provide from the host operating system and other containers.
  • Containers run only one operating system. This might be challenging for those who wish to run it on multiple operating systems.

Virtual machines pros

  • Virtual machines and associated tools are easier to access and work with. For instance, the Docker container supports numerous third-party libraries and tools.
  • Virtual machines allow you to initiate Docker instances. In other words, you can also run the Docker container within the virtual machine. This means that VMs and containers can co-exist.

Virtual machines cons

  • It will take you longer to migrate VM images between platforms or perform a successful backup. This is because VMs require more memory.
  • Physical servers support fewer virtual machines than containers.

Which one to use: Virtual machines or Containers

Containers are lightweight, and thus you can move them easily across private, hybrid, public, or multi-cloud environments as well as on bare-metal systems. They provide an ideal environment for the deployment of cloud-native applications.

These apps could consist of microservices created to meet the need for automated management and consistent development experience across different environments.

Therefore, you can choose containers when you need to:

  • Package microservices.
  • Move scalable information technology projects across different IT footprints that share the same operating system.
  • Instill CI/CD or DevOps practices.
  • Build cloud-native applications.

Virtual machines can run more operations than a single container. That is why VMs are best suited for running large monolithic apps. However, their expanded functionality makes them less portable. This functionality also depends on the OS, libraries, and applications.

Virtual machines are best applicable when:

  • Running different operating systems inside other operating systems. For example, running Unix on Linux.
  • Housing traditional monolithic, legacy workloads.
  • Isolating risky development cycles.
  • Provisioning infrastructure resources, including servers, data, and networks.


Virtual machines and containers play significant roles in today’s society. These two technologies differ in many ways.

The most notable one is that containers allow users to virtualize an operating system, thus, allowing multiple workloads to run on a single operating system instance.

Virtual machines virtualize hardware resources to run on multiple operating system instances.

Happy learning!

Peer Review Contributions by: Wanja Mike