Docker and Kubernetes serve complementary functions: Docker for container creation, Kubernetes for orchestration
In cloud computing, containers abstract apps from the computers that run them and the operating systems which run those computers. Containers pack all the code and dependencies an application needs. As such, they operate with considerably less computing overhead than Virtual Machines (VMs) and VM hypervisors because they use the device’s host common operating system, binaries and libraries.
Containerized apps can be spun up and spun down almost instantaneously based on demand and resources. This makes it possible for containerized apps to work dynamically, at whatever scale the business needs, across multiple server clusters and data centers. Containerized apps can also be continuously optimized and changed throughout their lifecycle (a DevOps principle known as Continuous Integration/Continuous Deployment, or CI/CD).
Creating, deploying and managing containerized apps requires specialized software. Myriad cloud computing container app creation and management tools and technology are available. Here we’ll focus on two popular containerization technologies used presently: Docker and Kubernetes.
Both Docker and Kubernetes serve complementary containerizing functions. Docker is a method for packaging and distributing a containerized app, while Kubernetes is an orchestration system designed to deploy and manage containerized apps at scale.
Docker helps containerize
Docker is an open-source containerization Platform as a Service (PaaS). Docker provides developers with a way to build and run containers, store their images and share them. While the Docker platform project itself is open-source, a commercial company also sells Docker software. Developers don’t need Docker to make containers, but Docker simplifies containerization by automating the process and making it accessible using an Application Programming Interface (API).
“Docker enables you to separate your applications from your infrastructure, so you can deliver software quickly. With Docker, you can manage your infrastructure in the same ways you manage your applications. By taking advantage of Docker’s methodologies for shipping, testing and deploying code quickly, you can significantly reduce the delay between writing code and running it in production,” explained Docker.
“Docker provides an open standard for packaging and distributing containerised applications. Using Docker, you can build and run containers and store and share container images,” said Microsoft.
So, Docker is used by developers to containerize apps. Docker offers an orchestration system called Docker Swarm, which is a more direct comparison to Kubernetes. But Docker container can be used with Kubernetes, or another container orchestration system, in a production cloud computing environment.
Kubernetes manages and orchestrates containers
Containerized apps don’t work across cloud computing data centers on their own. To manage them, businesses use orchestration systems. Orchestration systems scale containerized apps up and down depending on service demand and available resources. The orchestration system also handles network communication, load balancing between available computing clusters and other requirements of containerized apps running in cloud computing environments.
Kubernetes, or K8s, is an open-source container orchestration system. Developed by Google, Kubernetes is one of the most popular container orchestration systems in use.
“Kubernetes is a portable, extensible, open-source platform for managing containerized workloads and services, that facilitates both declarative configuration and automation. It has a large, rapidly growing ecosystem. Kubernetes services, support and tools are widely available,” said The Kubernetes Authors.
Kubernetes gathers containerized apps in “pods,” the basic functional unit of a Kubernetes installation.
“Pods are the atomic unit on the Kubernetes platform. When we create a Deployment on Kubernetes, that Deployment creates Pods with containers inside them (as opposed to creating containers directly). Each Pod is tied to the Node where it is scheduled, and remains there until termination (according to restart policy) or deletion. In case of a Node failure, identical Pods are scheduled on other available Nodes in the cluster.,” explained the Kubernetes Authors.
Nodes work together in clusters.
“A Node is a worker machine in Kubernetes and may be either a virtual or a physical machine, depending on the cluster,” said the Kubernetes Authors.
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