Creating a Local Kubernetes Cluster from the Ground Up

From the ground up? Yep, from the ground up!

Overview

Creating a Kubernetes cluster can be tricky.

There are multiple tools designed just for that job. There are even companies that provide "installing K8s" as a service. And, to create a production-ready Kubernetes cluster with all the best practices in mind requires detailed designing and planning.

So, the scope of this article isn't to help you to create a "production-ready" cluster.

However, after reading this article, you should be able to create a local "testing" Kubernetes cluster, and for the developing and testing of DevStream, it should more than suffice.

Even for a local testing cluster, there are multiple tools you can choose from. For example, there is minikube, and there is kind. kind is a tool for running local Kubernetes clusters using Docker container nodes. kind was primarily designed for testing Kubernetes.

In this article, we are going with kind. We are not opinionated; we are not saying that kind is better than minikube or vice versa; we are merely choosing a tool to get the job done. If you are more familiar with other tools, it's completely fine!

This article uses macOS as our local development environment. If you are using Windows or Linux, you can still read this post to get a general idea and achieve the same.

Install Docker

Docker works in a way using Linux's Namespace and Cgroup. It's quite easy to install Docker on Linux. On macOS and Windows, Docker runs with virtualization. However, we do not need to worry too much detail here, because it's quite simple to download and run Docker Desktop.

Go to https://www.docker.com/products/docker-desktop, find the correct version of Docker Desktop (Intel/amd64, or M1/arm64):

Double click on the Docker.dmg file, and we see the installation interface like the following:

Simply drag "Docker" to our "Applications," and within a few seconds, it's done! We can start it from the Launchpad:

Wait a few seconds and we can see the starting page:

Click the gear" icon to change settings about Docker Desktop. For example, if we need to run a lot of containers, we might need to increase the memory. Here, we changed the memory to 4.00 GB:

Remember to "Apply & Restart" to ensure the changes are effective.

Introduction to kind

kind (Kubernetes-in-docker) uses a Docker container as a "node" to deploy Kubernetes. It's mainly used for testing Kubernetes itself.

kind is simple, containing a command-line tool named kind and a Docker image which has Kubernetes and systemd. kind uses Docker on the host machine to create a container, which runs systemd, which in turn runs the container runtime, kubelet, and other Kubernetes components. So, we end up with a whole Kubernetes cluster in one container.

Note that although in the explanation above, the Cluster is only a single node cluster, it's possible to create a multi-node Kubernetes cluster.

Creating a Kubernetes Cluster with Kind at the Click of a Button

1. clone DevStream's repo: https://github.com/devstream-io/devstream
2. cd devstream; make e2e-up

That's it.

If you check out the Makefile, you will see it actually runs a shell script that runs kind to create the cluster.

However, you wouldn't be satisfied if we end this article right here, right now, would you.

So, let's have a deep dive into kind. Fasten your seat belt, because we are gonna fly!

Creating a Kubernetes Cluster with Kind at Two Clicks of a Button

On GitHub, we can find the latest release of kind: https://github.com/kubernetes-sigs/kind/releases.

Choose relatively new versions, and install:

# method 1: download pre-compiled binarycd /tmpcurl -Lo ./kind https://github.com/kubernetes-sigs/kind/releases/download/v0.12.0/kind-darwin-arm64chmod +x ./kindsudo mv kind /usr/local/bin/# method 2: go get and compile locallygo get sigs.k8s.io/[email protected]

We can also download the Docker image beforehand. Here we choose v1.22 of Kubernetes:

kindest/node:v1.22.0@sha256:b8bda84bb3a190e6e028b1760d277454a72267a5454b57db34437c34a588d047

Create cluster:

kind create cluster --image=kindest/node:v1.22.0 --name=dev

Sample output:

Creating cluster "dev" ...  Ensuring node image (kindest/node:v1.22.0)   Preparing nodes   Writing configuration   Starting control-plane   Installing CNI   Installing StorageClass Set kubectl context to "kind-dev"You can now use your cluster with:kubectl cluster-info --context kind-devHave a question, bug, or feature request? Let us know! https://kind.sigs.k8s.io/#community 

Follow the hints above, next, let's run kubectl cluster-info --context kind-dev to switch the context and make sure you are in the right Kubernetes context.

$ kubectl get nodeNAME                STATUS   ROLES                  AGE    VERSIONdev-control-plane   Ready    control-plane,master   7m4s   v1.22.0$ kubectl get pod -n kube-systemNAME                                     READY    STATUS     RESTARTS      AGEcoredns-78fcd69978-hch75                  1/1     Running       0          10mcoredns-78fcd69978-ztqn4                  1/1     Running       0          10metcd-dev-control-plane                    1/1     Running       0          10mkindnet-l8qxq                             1/1     Running       0          10mkube-apiserver-dev-control-plane          1/1     Running       0          10mkube-controller-manager-dev-control-plane 1/1     Running       0          10mkube-proxy-mzfgc                          1/1     Running       0          10mkube-scheduler-dev-control-plane          1/1     Running       0          10m

Now we have a local cluster for testing and developing Kubernetes.

Creating a Kubernetes Cluster with Kind at Three Clicks of a Button

A minimum highly-available Kubernetes cluster is composed of 3 nodes. In this section, let's see how to create a multi-node, highly-available cluster locally using kind.

kind Cluster Config

We can pass a config file to kind by using the --config parameter. Let's have a look at a kind config file:

# this config file contains all config fields with comments# NOTE: this is not a particularly useful config filekind: ClusterapiVersion: kind.x-k8s.io/v1alpha4# patch the generated kubeadm config with some extra settingskubeadmConfigPatches:- |  apiVersion: kubelet.config.k8s.io/v1beta1  kind: KubeletConfiguration  evictionHard:    nodefs.available: "0%"# patch it further using a JSON 6902 patchkubeadmConfigPatchesJSON6902:- group: kubeadm.k8s.io  version: v1beta2  kind: ClusterConfiguration  patch: |    - op: add      path: /apiServer/certSANs/-      value: my-hostname# 1 control plane node and 3 workersnodes:# the control plane node config- role: control-plane# the three workers- role: worker- role: worker- role: worker

We can see that the config has two sections: the upper part being kubeadm related stuff and the lower part being nodes related settings. Apparently, the "nodes" part is where we are going to edit to achieve a multi-node cluster.

1 Control Plane Node, 3 Worker Nodes Cluster

Let's create a config named multi-node-config.yaml with the following content:

kind: ClusterapiVersion: kind.x-k8s.io/v1alpha4nodes:- role: control-plane- role: worker- role: worker- role: worker

Then run:

$ kind create cluster --config multi-node-config.yaml \ --image=kindest/node:v1.22.0 --name=dev4

We will get some output similar to the previous single-node cluster output, except for the "Joining worker nodes" part:

Creating cluster "dev4" ...  Ensuring node image (kindest/node:v1.22.0)   Preparing nodes      Writing configuration   Starting control-plane   Installing CNI   Installing StorageClass   Joining worker nodes Set kubectl context to "kind-dev4"You can now use your cluster with:kubectl cluster-info --context kind-dev4Thanks for using kind! 

Let's run the following command to check out our new cluster:

$ kubectl cluster-info --context kind-dev4Kubernetes control plane is running at https://127.0.0.1:51851CoreDNS is running at https://127.0.0.1:51851/api/v1/namespaces/kube-system/services/kube-dns:dns/proxyTo further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.$ kubectl get nodeNAME                 STATUS   ROLES                  AGE     VERSIONdev4-control-plane Ready   control-plane,master 3m28s   v1.22.0dev4-worker          Ready    <none>                 2m54s   v1.22.0dev4-worker2         Ready    <none>                 2m54s   v1.22.0dev4-worker3         Ready    <none>                 2m54s   v1.22.0

From the result above, we can see that this cluster has 1 control plane node and 3 worker nodes.

3 Control Plane Nodes, 3 Worker Nodes, Highly Available Cluster

Note: "Highly available" here only means that we have three control plane nodes. It's not strictly "highly available" because apparently, the three control plane nodes are actually on the same host, so when the host is down, everything is gone.

Prepare the ha-config.yaml with the following content:

kind: ClusterapiVersion: kind.x-k8s.io/v1alpha4nodes:- role: control-plane- role: control-plane- role: control-plane- role: worker- role: worker- role: worker

Run:

$ kind create cluster --config ha-config.yaml \ --image=kindest/node:v1.22.0 --name=dev6

We can see familiar outputs, with the exception being "Configuring the external load balancerJoining more control-plane nodes":

Creating cluster "dev6" ...  Ensuring node image (kindest/node:v1.22.0)   Preparing nodes        Configuring the external load balancer   Writing configuration   Starting control-plane   Installing CNI   Installing StorageClass   Joining more control-plane nodes   Joining worker nodes Set kubectl context to "kind-dev6"You can now use your cluster with:kubectl cluster-info --context kind-dev6Have a nice day! 

Some fun facts:

• the number of boxes after "Preparing nodes" equals the number of nodes
• the final greeting message is different: it was "Thanks for using kind! " previously and now it's "Have a nice day! "

Heck, those kind developers sure went some extra miles to enhance the user experience!

Check the cluster:

$ kubectl cluster-info --context kind-dev6Kubernetes control plane is running at https://127.0.0.1:52937CoreDNS is running at https://127.0.0.1:52937/api/v1/namespaces/kube-system/services/kube-dns:dns/proxyTo further debug and diagnose cluster problems, use 'kubectl cluster-info dump'.$ kubectl get nodeNAME                  STATUS   ROLES                  AGE     VERSIONdev6-control-plane    Ready    control-plane,master   8m19s   v1.22.0dev6-control-plane2   Ready    control-plane,master   7m46s   v1.22.0dev6-control-plane3   Ready    control-plane,master   7m20s   v1.22.0dev6-worker           Ready    <none>                 7m      v1.22.0dev6-worker2          Ready    <none>                 7m      v1.22.0dev6-worker3          Ready    <none>                 7m      v1.22.0

We can see this cluster has 3 control plane nodes.

So far, we have mastered how to use kind to create a multi-node Kubernetes cluster locally.

Advanced kind Features

Now that we know how to create clusters using kind, let's have a look at some advanced operations which could help you better use the clusters.

Port Mapping

Imagine you are running an Nginx container listening on port 8080 in a kind cluster but you wish the outside world (outside of the cluster) to access the Nginx port. To achieve this, we can add the extraPortMappings configuration:

kind: ClusterapiVersion: kind.x-k8s.io/v1alpha4nodes:- role: control-plane  extraPortMappings:  - containerPort: 8080    hostPort: 8080    listenAddress: "0.0.0.0"    protocol: tcp

In this way, the port on the pod 8080 is mapped to the port on the host.

Expose kube-apiserver

Sometimes we want to install Kubernetes with kind on one host, but access the cluster from another host. By default, the kube-apiserver installed by kind listens on 127.0.0.1 (with a random port.) To make the kind cluster accessible from another host, we need to make kube-apiserver listen on a network interface (for example, eth0.)

In the config file, we add networking.apiServerAddress. The IP is your local nic's IP:

kind: ClusterapiVersion: kind.x-k8s.io/v1alpha4networking:  apiServerAddress: "192.168.39.1"

Enable Feature Gates

Feature gates are a set of key=value pairs that describe Kubernetes features that are only available in Alpha, Beta or GA stage.

If we want to try some of those features, we can enable Feature Gates. In the config file, use:

kind: ClusterapiVersion: kind.x-k8s.io/v1alpha4featureGates:  FeatureGateName: true

Importing Images

Because the Kubernetes cluster is in fact running in a Docker container, by default, it can't access Docker images that are on the host. However, we can import those images from hosts to the Kubernetes cluster created by kind:

# import my-image:v1kind load docker-image my-image:v1 --name dev# import my-image.tarkind load image-archive my-image.tar --name dev

With this method, when we are building a new Docker image on the host which we want to run in a kind Kubernetes cluster, we can:

docker build -t my-image:v1 ./my-image-dirkind load docker-image my-image:v1kubectl apply -f my-image.yaml

How to see the images that are available in the kind Kubernetes cluster? Easy:

docker exec -it dev-control-plane crictl images

dev-control-plane is the name of the kind cluster.

You can also use crictl -h to see all the supported commands. For example, we can delete an image by using crictl rmi <image_name>.

Summary

Have fun playing with Kubernetes locally!

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