⚠️ This document would not work on Lastest Ubuntu 22.04: We get into https://kubernetes.io/docs/tasks/administer-cluster/dns-debugging-resolution/#known-issues

Setting up three node Kubernetes cluster

First of all, we should have three instances created that can connect over the public network. It doesn't matter how those instances are created, for example, they can either be Digital Ocean droplets or AWS EC2 instances.

SSH into all the instances

Once you are into those instances, the commands that are mentioned below should be run on all the instances

Commands to run on all the nodes

# Get sudo working
sudo -l

# update packages and their version
sudo apt-get update && sudo apt-get upgrade -y

# install curl and apt-transport-https
sudo apt-get update && sudo apt-get install -y apt-transport-https curl

# add key to verify releases
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -

# add kubernetes apt repo
cat <<EOF | sudo tee /etc/apt/sources.list.d/kubernetes.list
deb https://apt.kubernetes.io/ kubernetes-xenial main
EOF

# install kubelet, kubeadm and kubectl
sudo apt-get update
sudo apt-get install -y kubelet kubeadm kubectl

# install docker
sudo apt-get install docker.io

# apt-mark hold is used so that these packages will not be updated/removed automatically
sudo apt-mark hold kubelet kubeadm kubectl

After the above commands are successfully run on all the worker nodes. Below steps can be followed to initialize the Kubernetes cluster.

On Leader Node

Run the below command on the node that you want to make the leader node. Please make sure you replace the correct IP of the node with IP-of-Node

export MASTER_IP=<IP-of-Node>
kubeadm init --apiserver-advertise-address=${MASTER_IP} --pod-network-cidr=10.244.0.0/16

Join worker nodes to the Leader node

Once the command kubeadm init is completed on the leader node, below we would get a command like below in the output of kubeadm init that can be run on worker nodes to make them join the leader node.

kubeadm join 206.189.134.39:6443 --token dxxfoj.a2zzwbfrjejzir4h \
    --discovery-token-ca-cert-hash sha256:110e853989c2401b1e54aef6e8ff0393e05f18d531a75ed107cf6c05ca4170eb

Install CNI plugin

The below command can be run on the leader node to install the CNI plugin

kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

Setting up Kubeconfig file

After successful completion of kubeadm init command, like we got the kubeadm join command, we would also get details about how we can set up kubeconfig file.