Today I will show you the power of minimalism⌗

at first we will talk about Kubernetes a bit
then we will talk about what is k0s and comparing it to it’s alternatives
next I will show you two simple example of making a cluster on a single node or using k0sctl

Before reading this section you should have a bit knowledge about docker

Let’s talk about Kubernetes a bit⌗

K8s is a container orchestrator it’s like a conductor for containers to manage your cluster and for example decide witch container should go where.

in Kubernetes we are not interacting with containers directly we have lots of resources they have they own usage to fit in all of your scenarios. if you need a resource type that you need and it’s not inside kubernetes by default we have CustomResourceDefinitions

in K8s our tiniest resource is Pod, this resource can contain one or more containers inside it.

but we are not going to create them most of the times we will apply Deployment, StatefulSet, DaemonSet, etc.

I can’t talk about all of them here but if you don’t have a knowledge about them go and checkout Kubernetes Website

K0s⌗

k0s is a minimal kubernetes cluster they call it The Zero Friction Kubernetes made by mirantis the creator of Lens kubernetes IDE

instead of docker k0s is using raw containerd this will make it hard sometimes but images are fully compatible with each other because the manifest of images in all of the container runtimes are standard containerd architecture

I think it also give you an option to apply helm charts with it’s own CustomResourceDefinitions

so using containerd makes it a lot smaller

but why not using normal Kubernetes?⌗

when you want a cluster to be easy to run and being small in size and work with low hardware usage a normal K8s cluster is not what we want they made K8s as minimal as possible by keeping it’s stability

For example a Raspberry Pi Cluster

what are the alternatives to K0s?⌗

microk8s by canonical
K3s by Rancher Team (creator or Rancher and RKE)

I have tried all of them but K0s was more easy and more productive

Requirements?⌗

It works in everywhere but for more details check out this link

Let’s install a sample cluster⌗

install any Linux-Based Operating System on your nodes
then select one of the installation ways (Single Node, k0sctl, Raspberry Pi 4, Ansible, etc.) Now I will show you Single Node and k0sctl since they are recommended

the instructions below is from the official documents with a bit of my experience on top of that

Single Node

you should run all of the commands as root user or using sudo

at first we need to install k0s binary (it’s the only thing that we will install on nodes in everyway of installation) by running command below on our node:

curl -sSLf https://get.k0s.sh | sudo sh

Drink a coffee until installation finishes

confirm the installation by running k0s command without any option it will show you help of the k0s command

k0s install command is used when installing a node run the command below to install it as a single node cluster

k0s install controller --single

to start it run the command below

k0s start

command below will show you status of the cluster

k0s status

k0s kubectl is used for interacting with your cluster

if you want kubeconfig file it’s in /var/lib/k0s/pki/admin.conf

k0sctl

if you have production usage or automation on top of your installation you need this type of installation

the picture below will show you how k0sctl works

how k0sctl works

first we need to install k0sctl command; just go to this link and grab a binary that is compatible with your Operating System and put it in one of the directories that is listed inside your $PATH

don’t install it inside you target nodes

first we need access to root user of the nodes (putting your ssh-key should be enough) make sure you can access to all nodes without entering you ssh password.

next run the command below to create a sample file and then modify it

k0sctl init > k0sctl.yaml

open k0sctl.yaml file with the editor that you love :)

the file will be something like this:

apiVersion: k0sctl.k0sproject.io/v1beta1
kind: Cluster
metadata:
  name: k0s-cluster
spec:
  hosts:
  - role: controller
    ssh:
      address: 10.0.0.1 # replace with the controller's IP address
      user: root
      keyPath: ~/.ssh/id_rsa
  - role: worker
    ssh:
      address: 10.0.0.2 # replace with the worker's IP address
      user: root
      keyPath: ~/.ssh/id_rsa

hosts section is an array of your host add them as many as you want
keyPath is the address of your ssh private key
role can be one of:
- controller - a controller host
- controller+worker - a controller host that will also run workloads
- single - a single-node cluster host, the configuration can only contain one host
- worker - a worker host
sometimes controller+worker option will not make node to accept workloads I will show you how you can fix it later on

more info on the configuration file is here

when your configuration file is ready run the command below

k0sctl apply --config k0sctl.yaml

this will install and deploy your cluster

to access your cluster run the command below to get your kubeconfig

k0sctl kubeconfig > kubeconfig

this command will put it inside a file called kubeconfig

checkout your cluster status by running

kubectl --kubeconfig kubeconfig get all -A

and

kubectl --kubeconfig kubeconfig get nodes

if you specified controller+worker but workloads are pending run the command below

kubectl --kubeconfig kubeconfig taint nodes controlplane node-role.kubernetes.io/master:NoSchedule-

some notes:

k0sctl can only add more nodes to the cluster. It cannot remove existing nodes.
running k0sctl apply again command will just apply changes to the cluster.

Minimal K8s Cluster Using K0s

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