What is the difference between Kubernetes vs Docker

Nowadays we hear a lot about Kubernetes vs Docker but it is a quite misleading phrase. We will understand what people mean to say when they talk about Docker vs Kubernetes. As they both are not direct competitors. Docker is a containerized platform whereas Kubernetes is a container orchestrator for container platforms like Docker.

It’s not correct if we talk about docker without exploring containers. Containers solve critical issues of application development. We developers always face an issue when our code is running perfectly on the local environment but not on production. There can be multiple reasons behind it like different operating systems, different dependencies or can be different libraries. This problem can be solved with the help of containers as a developer can package up their application, including all the bins and libraries it needs to run correctly, into a small container image. And on production, we can use that image to run the application in any containerized platform. Containers are portable and scalable and can be scaled on the basis of our requirements.

In addition, scalability and portability containers provide many advantages over traditional virtualization. It has a small footprint and it requires only application and definition of bins and libraries. Unlike Virtual machines which have a complete copy of the guest operating system whereas in containers separation is done on kernel level without the need for a guest operating system. Containers don’t need to have multiple instances if all the applications are using the same libraries/packages. It allows an application to become encapsulated in a self-contained environment that allows for quicker deployments, closer parity between development environments, and infinite scalability.

Now, we are aware of what containers are, let's explore what is docker?

Docker is the most popular container platform and the main reason for its popularity is its open source. Docker allows us to build and run containers but before running a container we need to create a docker file that contains all the OS network specifications, and file locations. If you don’t want to create a docker image from scratch you can check the docker hub to find the image on the basis of your requirement. There you can also share your image.

Docker provided an open standard for packaging and distributing containerized applications but now there is a new problem. How would you coordinate and schedule multiple containers? How do you seamlessly upgrade an application without any interruption of service? How do you monitor the health of an application, know when something goes wrong and seamlessly restart it? Here, orchestrating containers like Kubernetes, docker swarm came to your rescue. These provide you with abstraction to make a cluster of a machine and behaves like one big machine, which is vital in a large scale environment.

So, now we will understand what people exactly mean when they use a phrase like Docker vs Kubernetes. They actually mean Kubernetes vs Docker Swarm. The latter is Docker’s native clustering solution for Docker containers which has the advantage of being tightly integrated into the ecosystem of Docker and uses its own API. It allows to spread a large number of clusters across the servers.

What is Kubernetes and how is it used?

It is the container orchestrator that was developed by Google and later being open-sourced. It is a comprehensive system for deployment, scheduling and supports many containerized tools such as docker.

It is a new standard way of orchestrating containers and deploying the distributed application. It can be run on public cloud service or on-premise and it is highly modular with a vibrant community.

In layman’s language, Kubernetes can be described as a control loop. If you want three images of the container a and two images of container b then Kubernetes can make it happen. It compares the desired state to the actual state and if both are not the same it takes steps to correct it.

          Kubernetes as a controlled loop

How Docker is related to Kubernetes?

Kubernetes and Docker are both comprehensive and intelligent solutions for managing containerized applications which provide powerful capabilities, and from this, there are a lot of confusions. “Kubernetes” is now sometimes used as a shorthand for an entire container environment based on Kubernetes. In reality, they are not directly comparable, they deal with the different problems, are interdependent on each other in some cases and solve different issues independently.

Docker is a platform and tool for building, distributing and running Docker containers. It offers its own native clustering tool that can be used to orchestrate and schedule containers on machine clusters and the tool is known as Docker swarm. Kubernetes is a container orchestration system for Docker containers that is more extensive than Docker Swarm and is meant to coordinate clusters of nodes at scale in production in an efficient manner. Kubernetes can run with multiple nodes across the server. It works around the concept of pods, which are scheduling units (and can contain one or more containers) in the Kubernetes ecosystem, and they are distributed among nodes to provide high availability. One can easily run a Docker build on a Kubernetes cluster, but Kubernetes itself is not a complete solution and is meant to include custom plugins. Kubernetes requires docker to provide an efficient and scalable solution.

Kubernetes and Docker are both fundamentally different technologies but they work very well together, and both facilitate the management and deployment of containers in a distributed architecture.

What is the difference between Docker and Kubernetes?

We had read earlier that it is easy to compare Docker with Kubernetes as one is used to create containers where the other is used to create container orchestrator. So for a better comparison, we should compare Kubernetes vs Docker Swarm as they both are container orchestrator technologies.

Docker Swarm is naturally tightly integrated within the Docker ecosystem and focuses on the clustering of Docker containers.

The major difference between Docker and Kubernetes is that Docker runs on a single node, whereas Kubernetes is designed to run on multiple nodes (across a cluster).

Another major difference between Kubernetes and Docker is that Docker can be used without Kubernetes as it is a container system, whereas Kubernetes needs a container runtime in order to orchestrate.

Can we use Docker without Kubernetes or Vice-versa?

As we read above Docker is used for making your application containerized so it is commonly used without Kubernetes that is the norm. Kubernetes offers us a lot of additions but it makes it quite complex and there are many scenarios where adding the Kubernetes is overkill or unnecessary.

While developing the application it is common to use docker without a container orchestrator like Kubernetes. Whereas in production environments a container orchestrator can benefitable and does not outweigh the cost of added complexity. If we are using some public cloud services like AWS, GCP, and Azure they provide some orchestration capabilities which are making the tradeoff of the added complexity unnecessary.

Whereas Kubernetes is a container orchestrator and it needs a container or docker runtime in order to orchestrate. Basically, Kubernetes is most commonly used with Docker, but it can also be used with any container runtime. Some examples of other containers which you can deploy with runtime are RunC, cri-o. You can get the proper documentation to set up ContainerD and Cri-o on Kubernetes official documentation.