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Docker helps you build container images and run containers; Kubernetes coordinates containerized workloads across a cluster. Kubernetes still runs images built with Docker, but a cluster node needs a runtime that implements the Container Runtime Interface (CRI). The built-in Docker Engine integration, dockershim, was removed in Kubernetes 1.24.
What Docker does
Docker Engine is an open-source containerization technology for building and containerizing applications. Its daemon manages images, containers, networks, and volumes. Those objects serve different roles: an image is a reusable packaged artifact, while a container is a running instance created from an image. Docker’s Engine documentation describes the engine and the objects it manages.
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How Docker fits into Kubernetes
Kubernetes schedules and coordinates workloads across cluster nodes. Each node needs a container runtime that communicates with Kubernetes through the Container Runtime Interface (CRI). This is a separate concern from which tool built the image.
Does Kubernetes still use Docker?
Docker-built images remain usable in Kubernetes. What changed was the integration used by nodes to run containers: Kubernetes removed its built-in dockershim integration in version 1.24. The Kubernetes project explained the distinction in its December 2, 2020 article, “Don’t Panic: Kubernetes and Docker”: “Docker is still a useful tool for building containers, and the images that result from running docker build can still run in your Kubernetes cluster.” The current Kubernetes container runtime documentation describes the CRI requirement and runtime options.
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What dockershim’s removal means
Before Kubernetes 1.24, dockershim let Kubernetes communicate directly with Docker Engine. That built-in component was removed; it did not make Docker-built images unusable or prohibit using Docker during development. If an operator specifically wants Docker Engine as the node runtime, Kubernetes documents the cri-dockerd adapter as a way to provide the CRI integration. See the runtime documentation and the dockershim removal FAQ for the current explanation.
Do you need Docker to learn Kubernetes?
You need to understand images and containers, but Docker Engine is not a universal requirement for learning Kubernetes. Docker is one tool for building and working with images; Kubernetes clusters use a CRI-conforming runtime on their nodes. Learning the image-versus-container distinction and the separation between image tooling and node runtime will make Kubernetes concepts easier to follow.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Can you use Docker Desktop for local Kubernetes?
Docker Desktop offers a local Kubernetes server and client for development and testing. Its documentation describes different cluster options: its kubeadm-based option is single-node, while kind can provision multiple nodes and lets you select the Kubernetes version and node count. Docker characterizes its built-in option as slower to provision than kind and documents an Enhanced Container Isolation limitation. Cluster behavior and limitations can change, so consult the current Docker Desktop Kubernetes documentation before choosing a setup.
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