Kubernetes vs Docker

In an era where container technologies have taken the industry by storm, one of the most common online searches on the topic of containers is ‘Kubernetes vs Docker’. The relevance and accuracy of this comparison is questionable, as it is not really comparing apples to apples. In this blog post, we will attempt to clarify both terms, present their commonalities and differences, and help users better navigate the ever-growing container ecosystem.

What are containers?

Let’s start with a short definition of containers. Containers package application software with their dependencies in order to abstract it from the infrastructure it runs on. A containerised application can be deployed easily and consistently on a local machine, a private data centre, a public cloud, or any other compute infrastructure. They are often compared to virtual machines (VMs), as they provide similar resource isolation and allocation capabilities. Containers are more lightweight and portable than VMs, as they only virtualise the operating system instead of the hardware layer. Containers are a standard feature of the Linux kernel since the introduction of cgroups by Google in 2006.

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What is Docker?

Docker was launched in 2013 by Docker, Inc. as an open source containerisation platform. It promised an easy way to build and deploy containers on the cloud or on-premises and is compatible with Linux and Windows. Although Docker did not introduce a new concept, its ‘new way to deploy software’ and ‘faster time-to-market’ messaging appealed to users so much that Docker soon became shorthand for containers and the default container format.

Docker streamlines the creation of containers with tools such as the dockerfile and docker-compose. It also helps developers move workloads from their local environment, to test up to production by removing the cross-environment inconsistencies and dependencies. This results in faster delivery of the software and an increase in quality. 

What is Kubernetes?

The evolution of container technology has led to the growth of its own popularity. Developers started to build and deploy containerised applications, breaking down monolithic apps into microservices for resource optimisation and easier maintenance. As a result, the industry saw a significant spike in the use of containers, and consequently, businesses were now facing new challenges in managing and deploying them.

Enter Kubernetes, an open-source project made available by Google in 2014. Kubernetes is an orchestrator of container platforms, such as Docker. Kubernetes allows users to define the desired state of their container architecture deployment on various substrates. Following user input, Kubernetes can deploy and manage multi-container applications across multiple hosts, taking action if needed to maintain the desired state. This level of automation has revolutionised the container space as it created the framework for features such as scalability, monitoring and cross-platform deployments.

What is the relationship between Docker and Kubernetes?

So if ‘Docker is containers’ and ‘Kubernetes is container orchestration’ why would anyone ask “Should I use Docker or Kubernetes”? In reality, the two tools are actually complementary to each other and help build cloud-native or microservice architectures. 

Docker is mostly used during the first days of a containerised application. It actually helps build and deploy the application’s container(s). In cases where the application’s architecture is fairly simple, Docker can address the basic needs of the application’s lifecycle management. 

In cases where the application is broken down into multiple microservices, each one with their own lifecycle and operational needs, Kubernetes comes into play. Kubernetes is not used to create the application containers; it actually needs a container platform to run, Docker being the most popular one. Kubernetes integrates with a large toolset built for and around containers and uses it in its own operations. Containers created with Docker or any of its alternatives can be managed, scaled and moved by Kubernetes, which also ensures failover management and health maintenance of the system. 

There are great benefits to using Kubernetes with Docker:

• Applications are easier to maintain as they are broken down into smaller parts
• These parts run on an infrastructure that is more robust and the applications are more highly available
• Applications are able to handle more load on-demand, improving user experience and reducing resource waste. As applications become more scalable, there is no need to pre-allocate resources in anticipation of load peak times.

Both Docker and Kubernetes are backed by strong open-source communities and are part of the Cloud Native Computing Foundation (CNCF), a Linux foundation project aiming to advance container technologies and align the industry around specific standards. 

Kubernetes vs Docker Swarm

Users often compare Kubernetes with Docker. Hopefully, we have now made clear the reasons why this isn’t a valid comparison. In order to compare two similar container technologies, one should look at Kubernetes vs Docker Swarm. Docker Swarm is Docker, Inc’s container orchestration solution. Swarm is tightly integrated into the Docker ecosystem and has its own API.

This tight integration is one of the advantages of Swarm over Kubernetes, as transitioning to it from Docker is quite easy. Kubernetes brings its own GUI, scoring points with users that are keener on using a graphical interface than the command line. In terms of tooling, Kubernetes is vastly richer, more extensible and customisable than Swarm, especially when it comes to system monitoring and auto-scaling. Overall, Swarm is considered a simpler solution that can be easier to get started and is suitable mainly for development use cases. Kubernetes is not tied to Docker, supports more complex workflows and is used significantly more frequently in production environments.

Conclusion

Containerised applications bring elastic scalability, isolation and portability, especially when comparing them to monolithic solutions. Docker provides an open standard to package and distribute containerised applications and is sufficient to address simple use cases. 

Businesses that have complex application architectures are moving to Kubernetes to handle their cross-infrastructure scalability and resilience needs. Kubernetes leverages a large tooling ecosystem along with continuous integration/continuous deployment (CI/CD) and other DevOps practices to orchestrate large sets of containers, from development to production environments. 

Using Docker and Kubernetes together can bring value for businesses looking to thrive in a cloud-native environment, as this reduces time-to-market, makes applications easier to maintain, and addresses traffic increases.

Learn more about Kubernetes by Canonical >