When we think containers, usually two names come to mind — Docker and Kubernetes.

At this point, many could assume there is some kind of a Docker vs Kubernetes rivalry out there. Since they are the biggest fish in the pond, they must be trying to eat each other, right?

Well, that’s not entirely correct.

Docker is an open platform, which is used to build, ship, and run distributed applications. In the meantime, Kubernetes is mostly about container orchestration.

The difference between Docker and Kubernetes is the following:

Docker builds and deploys containers, while Kubernetes orchestrates and manages multiple clusters of containers. This pretty much means that you should not pick between the two, but use them to complement each other.

So, what is this Kubernetes vs Docker conflict about, then?

Why is everybody so hyped about it?

Is there any ground for Docker vs Kubernetes rivalry whatsoever? (Spoiler alert: No, there is not. I will explain why below.)

In this post, I will let you in on the specifics of Docker and Kubenetes and do my best to clear up the confusion that’s been circulating around “Kubernetes vs Docker” controversy. But first, let’s clarify what a container is…

What Is a Container?

According to a definition by Docker:

A container is a standard unit of software that packages up code and all its dependencies so the application runs quickly and reliably from one computing environment to another.

Containerized applications in Docker

In the meantime, a Docker container image is:

A lightweight, standalone, executable package of software that includes everything needed to run an application: code, runtime, system tools, system libraries, and settings.

All of this means a few things:

  • Every container stores all moving parts that are required to run an application
  • Containers allow to abstract applications away from any environment — be it development, testing, staging, or production environment
  • Any manipulations with container-packaged code are not required to run it on different servers and in different environments

Containers are increasingly functional, agile, and lightweight. They are predictable, repeatable, and immutable. They ensure faster deployments, immense scalability, high flexibility, and elasticity.

Containers are a revolutionary technology for developers. They do not have to rely on “heavy” virtual machine images (traditional virtualization) to manage applications or their components across different environments and on different devices.

Containers are hugely beneficial not only to developers, though.

Containers can be run not only on Linux and Windows but also in the traditional datacenter and in the cloud. This is why they are a go-to technology when it comes to DevOps, cloud migration, distributed cloud computing, and microservices.

Other benefits of containers are:

  • Ease and efficiency of container image creation in comparison with Virtual Machine images
  • Cost-efficiency of resource utilization (app’s performance is predictable)
  • Integration with microservices (apps are deployed and managed dynamically)
  • Availability of detailed reports on OS metrics, app health, etc.
  • Separation of concerns between Dev and Ops

Basically, all of the factors above have played a part in widespread adoption of Docker.

What Is Docker?

Docker is an open source collection of tools designed to build, ship, and deploy software within containers in order to simplify the process of creating, deploying, and running applications.

Since containers ensure that any application can be efficiently packaged and run in any environment, Docker can be compared to a virtual machine. Yet, it is way more efficient.

Specifically, Docker allows you to execute a so-called Dockerfile — a separate file that specifies how a Docker image is built.

As shown below, the “docker run” command can be easily set off to launch the Docker image in the docker daemon.

How to run the Docker image in the Docker daemonYou can start up your Docker images in any environment or on any device with the docker daemon installed.

Note: Docker features a cloud repository for its images — Docker Hub. Use it to store and get quick access to your Docker images, or to distribute containers.

To learn more about Docker, check out “Introduction to Docker” video below:

Done? Let’s get to Kubernetes, then.

What Is Kubernetes?

Kubernetes is an open source platform, which provides a container-centric management environment and allows for the efficient orchestration of containerized workloads and services.

Kubernetes utilizes the master-slave architecture, as shown below:

Master-slave architecture of Kubernetes nodesIt allows you to run and manage multiple clusters of containers across multiple machines — a logical next step after the containers are built and spun up — while reducing overheads and operation burden.

Here are a few features of Kubernetes:

  • Ongoing “mass” orchestration of multiple containers
  • Scaling containers up or down based on the demand
  • Managing storage based on app’s instances
  • Sharing load across multiple containers
  • Starting up new containers if any containers fail
  • Canary deployments and rollback
  • Resource monitoring and logging

With no Kubernetes around, you would have to start up containers, manage their interactions, configure storage, and “clean” broken containers manually.

Kubernetes allows you to automate the orchestration of containerized software. It is automation that ensures that multiple containers always run across different machines.

To find out more technical details about Kubernetes, watch the video below:

Kubernetes is the leading container orchestration platform out there. No less than 60% of container users rely on Kubernetes for container orchestration. And yet, Docker has a few tricks up its sleeve.

Docker vs Kubernetes: What’s the Difference?

I suppose you have figured out already that there is no Docker vs Kubernetes conflict. They are just two different tools that act as independent pieces of a larger, interconnected system.

Kubernetes vs Docker: the connectionWhat is the big deal, then? Why is there so much hype around Kubernetes vs Docker?

The answer is simple:

Docker is not a single tool but a collection of tools. One of these tools — Docker Swarm — is an alternative to Kubernetes, which also does container orchestration.

Obviously, Kubernetes and Docker Swarm are not actually that similar.

Here is a quick overview of the two by Jayashree Hegde Adkoli in his “Docker Swarm vs. Kubernetes: What You Really Need To Know” post at Dzone.com:

Kubernetes Docker Swarm Comparison

In a nutshell: Kubernetes is more customizable than Docker Swarm. It is a container orchestration tool for those who want to manipulate settings and parameters on their own. On the other hand, Docker Swarm is more user-friendly; a perfect option for users who want to pack their apps into containers and to get them running without having to spin up an operating system.

Which one — Kubernetes or Docker Swarm — is winning the container orchestration war, then?

Kubernetes.

It continues to gain steam in 2018. Moreover, Docker has already started to support both Docker Swarm and Kubernetes.

Kubernetes is likely to remain an undisputed leader of container orchestration for years to come, with a larger part of the market pie under its control.

Kubernetes and Docker: Working in the Two Systems

As previously mentioned, Docker and Kubernetes are elements of a larger ecosystem, which is used to create and build a modern cloud architecture (among other things).

Kubernetes can be integrated with the Docker engine to support its build-ship-deploy capabilities by coordinating how containers are scheduled and executed.

To integrate Kubernetes into Docker, you need to know the CLI specs of both Docker and Kubernetes to access the data over API. Specifically, you will need the Docker CLI for navigation and the Kubernetes CLI for running and managing the programs.

In the Docker-Kubernetes ecosystem, Docker runs the container images while Kubernetes handles load balancing, networking, container setup, and service discovery.

Given that, both Docker and Kubernetes ensure the efficiency of the software development lifecycle. For instance, here is how a modern CI/CD pipeline using Docker and Kubernetes may look like:

CI/CD with Docker and KubernetesTo learn more details about working with Kubernetes and Docker, check out the SlideShare below:

Conclusion

Docker and Kubernetes are powerful tools that every developer, DevOps, and cloud professional must use.

Since they are different tools used at different levels of the SDLC, the Docker vs Kubernetes rivalry is pretty much non-existent. (Yet, Docker Swarm vs Kubernetes is the real thing.)

Therefore, it is key to practically work out the fundamental difference between Docker and Kubernetes, and to stop setting them off against each other.

These tools are perfect for multi-cloud environments and can be efficiently utilized for cloud migration and application modernization. Microservices would not have become a thing without them, too.

When used together, Docker and Kubernetes help build and deliver the highest quality software at the lowest cost in the shortest time.

Feel free to reach out to Squadex cloud professionals to facilitate the cloud transformation of your organization!

What are your thoughts about Docker and Kubernetes? Why is Docker vs Kubernetes rivalry still a thing? Share your feedback in the comments’ section!

Yevhen Duma

Senior DevOps Consultant at SQUADEX

Yevhen has more than ten years of professional IT experience, developing and delivering consumer and enterprise applications, infrastructure and process improvement projects for various scale businesses. His experience at all software development stages allows for better understanding of business needs and improved processes by utilizing established DevOps tools backed by the best Agile practices.

His area of expertise includes software development lifecycle, version control, CI/CD, Atlassian JIRA, Service Desk, Confluence, Bitbucket, Slack, Flowdock, as well as virtualization, cloud platforms, and their automation.