When searching for containerization solutions, Docker and Kubernetes are two popular vendors that will show up in the results. Because the two solutions are so popular, it’s easy to get them confused as they often seem to be used interchangeably, but they are in fact different technologies. Kubernetes is an orchestration tool to automate and organize container deployment, and Docker is the container solution used to run deployed applications. Usually, an organization can find both solutions in a containerized environment, but understanding the differences between them can help teams choose the solution that best fits the business requirements.
The term “container” and “Docker” are often used interchangeably, but Docker is the technology behind containers and the engine that runs them. It’s almost impossible to avoid finding Docker references when researching containerization, because Docker is the dominant technology on the market.
Before containerization was developed, developers had difficulties deploying applications along with dependencies and configurations necessary to run their applications. It was common for developers to deploy their applications to a virtual machine (VM), but any misstep in configurations or missing dependencies would result in errors. Containerization solved this issue by allowing developers to package their applications with all necessary configurations and dependencies into an image that can then be deployed on the host server. These images can be deployed to the cloud, an internal server, or another developer machine. Containers make software much more portable compared to deployment strategies that use other technologies such as virtual machines.
Docker is a technology that makes it possible to deploy containers to the developer’s chosen environment. It’s open-source and supported by every major cloud vendor (AWS, Azure, and GCP). The open-source nature of its codebase means that it’s been continually improved from community feedback and contributions. The technology can run on a virtual machine or physical server, so it’s supported in the cloud and on-premises. Docker containers run in a sandbox environment so that it does not affect other applications on the host server.
To run Docker images, the host server must have the Docker engine installed. Developers can then create a Docker File, which defines configurations for the container. Developers then deploy their application image to the target server. When it’s just one container and a simple image, developers can manually deploy their applications without much overhead, but enterprise development requires more streamlined, automated deployment to rapidly deploy numerous containers across different environments. This is where orchestration tools are beneficial.
Kubernetes (often referred to as “k8s”) is an orchestration tool used to deploy containers. If an enterprise uses containers, it’s likely they use Kubernetes to help automate the deployment process. It’s not necessary to have Kubernetes if the development team uses containers, but it’s beneficial when the deployment process needs refinement in scheduling and coordination between multiple environments and numerous container images.
Orchestration tools such as Kubernetes are used when the organization needs to scale their deployment process. It’s not uncommon for an enterprise to have multiple applications running in pools of containers hosted in the cloud. In a large-scale environment, scheduling, coordination, testing, and deployment for these containers can be a full-time job, which wastes developer resources. Kubernetes solves this problem by giving developers the ability to automate much of the process and destroy, create, and configure several containers simultaneously. Kubernetes allows developers to easily deploy new containers as they update their applications with new features and bug fixes.
Kubernetes was often compared to Docker Swarm, but Docker Swarm Enterprise was purchased and quietly phased out for the more dominant Kubernetes technology. Kubernetes is the market leader in orchestration in a containerized environment, and every major cloud platform supports it. You can also run Kubernetes on-premise if you host any application servers in-house.
In an enterprise environment, Kubernetes is a central tool that deploys all containers. The control plane is where developers can review their deployments, storage, configurations and schedules. Developers can also review active containers to get the current state of the application.
Two terms are used to describe the location where containers are deployed: nodes and pods. Nodes are the servers where the container engine runs. A node can be a physical server, a virtual machine (VM), or a cloud environment. You can have several nodes in a clustered hosting environment, which is common in the enterprise.
Pods are the virtual component that contain the Docker image and runs the container applications. You can have several containers running inside a single pod and a pool of pods running an application. Pods are deployed to nodes, and Kubernetes is the orchestration tool that deploys them. The automation behind deployment configures the resources for each pod such as CPU availability, storage and memory.
Using Kubernetes, a developer schedules a deployment. The Kubernetes master node takes the application image and configuration file and deploys the container to the environment. It then provides feedback to developers so that they can monitor success and identify any errors in deployment.
In smaller development environments, it’s possible to work with Docker containers with no orchestration tools including Kubernetes. Once the business grows and has several applications running in their own containers, orchestration reduces the time for deployment and reduces mistakes made when coordinating multiple deployment schedules.
Kubernetes has become the de facto standard in orchestration, but you can also choose to work with other orchestration tools. The major cloud providers offer their own tools that integrate well within their own platform, but using vendor-specific tools ties you to their services. Kubernetes will work in any environment including cloud provider platforms and an on-premise environment. Therefore, using Kubernetes allows you to migrate to a new platform service without vendor lock-in.
Docker and Kubernetes were often competitors, but with Docker Swarm Enterprise retirement, the two technologies work together as the industry standard. Fundamentally, Docker and Kubernetes are different technologies, but they work so well together that it’s common to find both in any containerized environment.