Create a Local Cluster

Instead of reading endless lines of documentation to understand the basics of Kubernetes, this guide is trying to be more hands-on.

We will start by creating a cluster. We will create this cluster locally and not use any cloud providers.

important

A local cluster will be different from a cloud based cluster in many ways. Load Balancer, persistent volumes, networking and routing will be different. You don't have to concern yourself with that for now. Just remember, this here, we are trying to get to know the building blocks.

To create a local cluster, we will use kind. Kind is a convenient way to launch all sorts of local clusters. It's quite resilient but it is NOT intended for production use. Long lived kind clusters tend to deteriorate. It's using docker containers to simulate nodes.

important

This project has a kind configuration that it uses, we'll get to that later.

Let's explore a cluster.

Run:

kind create cluster

What you should see looks something like this:

kind create cluster
Creating cluster "kind" ...
 ✓ Ensuring node image (kindest/node:v1.27.1) 🖼
 ✓ Preparing nodes 📦
 ✓ Writing configuration 📜
 ✓ Starting control-plane 🕹️
 ✓ Installing CNI 🔌
 ✓ Installing StorageClass 💾
Set kubectl context to "kind-kind"
You can now use your cluster with:

kubectl cluster-info --context kind-kind

Thanks for using kind! 😊

kubectl is your basic tool to explore clusters. A general move in every new environment is to immediately alias it to just k. alias k='kubectl'. This will save you a LOT of typing.

Your first command will be: k get pods -A.

The output looks something like this:

k get pods -A

NAMESPACE            NAME                                         READY   STATUS    RESTARTS   AGE
kube-system          coredns-5d78c9869d-rlbx8                     1/1     Running   0          3m9s
kube-system          coredns-5d78c9869d-vww68                     1/1     Running   0          3m9s
kube-system          etcd-kind-control-plane                      1/1     Running   0          3m22s
kube-system          kindnet-b2zwz                                1/1     Running   0          3m9s
kube-system          kube-apiserver-kind-control-plane            1/1     Running   0          3m22s
kube-system          kube-controller-manager-kind-control-plane   1/1     Running   0          3m24s
kube-system          kube-proxy-bgg6q                             1/1     Running   0          3m9s
kube-system          kube-scheduler-kind-control-plane            1/1     Running   0          3m22s
local-path-storage   local-path-provisioner-6bc4bddd6b-m95zz      1/1     Running   0          3m9s

You see the main building blocks of Kubernetes here. These are pods. The linked document has a nice explanation about what pods are. TL;DR would be that they are just containers or Linux namespaces. They can contain multiple containers, however, which makes them a little bit more than just a 1:1 with a single application. A single pod could run, for example, an application and the monitoring stack for that application inside the pod. Or a network router.

That said, you should usally restrict yourself from running too many containers in a single Pod. Mostly because they eat resources and increase the need of a single Pod.

tip

The keen observe notices the -A in that command. For now, you can ignore that. It means to list all pods in all namespaces.

Let's take a look at the nodes next:

k get nodes

NAME                 STATUS   ROLES           AGE   VERSION
kind-control-plane   Ready    control-plane   9m    v1.27.1

We have a single node right now. A node is basically a worker machine. Pods are scheduled in machines. We'll talk about how that happens later on. Scheduling is not an easy subject.

important

This part is incomplete. There are a lot of amazing posts now-a-days about the basic building blocks of Kubernetes. The purpose of this site is to give you some services to deploy and to play with.