KIND: Kubernetes in Docker #

kind is an awesome tool which lets us quickly spin up a k8s cluster where each server in the cluster is simulated as a docker container. This lets us very quickly spin up local clusters for testing applications and other purposes.

We haven’t interacted with any Kubernetes clusters yet (yes I know we went through a lot of theory 😅). This ends now, I assume you already got the tools installed which was mentioned in the chapter about Essential Tools, if not hurry up and get them installed.

Creating a cluster #

A cluster can be created using the following command.

kind create cluster

This will start a docker container which runs Kubernetes. In addition it will also set up the Kubernetes CLI kubectl. This enables us to use the CLI to interact with our local cluster.

If you want multiple separate clusters, you can run the command again and supply the --name flag which will let you give the cluster a name.

kind create cluster --name=my-cluster

Listing clusters #

To get a list of your current kind clusters run

kind get clusters

Deleting clusters #

To delete a cluster supply the name flag:

kind delete cluster --name=my-cluster

Loading images #

The container runtime inside your kind cluster doesn’t is in fact not the same as on your host machine. This comes to show if you build and image and try to run it in your cluster. Because the cluster isen’t running on the same container runtime as your host docker, it wont be able to find the images you build on your host. If running something from Dockerhub, this isen’t a problem, as the container runtime will simply fetch the image and run it.

But kind provides a small mechanism which lets us copy images from our host docker runtime to the container runtime within the kind cluster. To copy a docker image to your cluster run

kind load docker-image --name=my-cluster <image-name>

There is currently a bug, which causes trouble when using Docker Desktop with default settings. See the tracking issue for a workaround.

Exercises #

Creating a cluster with multiple nodes #

Kind supports a config file format which can be used for more advanced configurations. One of the options in the config file lets you specify what nodes your cluster should be made up of.

You can find the documentation for the kind config file here

• Create a config file which specifies a multi node cluster.
• Create a cluster based on the config file.
• Run docker ps to see that you have the nodes you expect.