How to Setup Multi-Node Kubernetes Cluster on Ubuntu

Kubernetes (often abbreviated as K8s) is an open-source platform designed to automate the deployment, management, and scaling of containerized applications. In simpler terms, it lets you group Linux container hosts into clusters and takes the hassle out of managing them. In this tutorial, I’ll walk you through setting up a multi-node Kubernetes cluster using multiple Ubuntu virtual machines on AWS. Let’s dive in!

Prerequisites

For this setup, I’ve launched three EC2 instances in an AWS account, all running Ubuntu and using the t3.medium instance type. Here’s the plan:

• One instance will serve as the Kubernetes control plane.
• The other two will act as worker nodes, where our containers will run.

Make sure you have your AWS key pair (e.g., your-key.pem) ready for SSH access.

Step 1: Set Up Hostnames and Network Configuration

First, we need to configure the instances so they can communicate properly. Let’s start by setting hostnames and updating the network settings.

1.1 SSH into Each Node

Connect to each EC2 instance using SSH. Replace <instance-ip> with the public IP of each instance:

ssh -i your-key.pem ubuntu@<instance-ip>

Repeat this for all three nodes.

1.2 Set Hostnames

Assign a unique hostname to each node to make them easily identifiable.

• Control Plane:

  sudo hostnamectl set-hostname k8s-control-plane
  

• Worker Node 1:

  sudo hostnamectl set-hostname k8s-worker-1
  

• Worker Node 2:

  sudo hostnamectl set-hostname k8s-worker-2
  

Run these commands on the respective nodes.

1.3 Update the Hosts File

To ensure the nodes can communicate using their hostnames, update the /etc/hosts file on all three instances. Open the file with:

sudo nano /etc/hosts

Add the following lines, replacing the IP addresses with the private IPs of your EC2 instances:

192.168.1.100  k8s-control-plane
192.168.1.101  k8s-worker-1
192.168.1.102  k8s-worker-2

Save and exit (Ctrl+O, Enter, Ctrl+X). Do this on every node.

Step 2: Install Docker and Kubernetes Components on All Nodes

Now, let’s install the necessary software on all three nodes. We’ll need Docker for container runtime and Kubernetes tools like kubeadm, kubelet, and kubectl.

2.1 Update Packages

Start by refreshing the package list and upgrading existing packages:

sudo apt update && sudo apt upgrade -y

2.2 Install Dependencies

Install some required packages for secure downloads:

sudo apt install -y apt-transport-https ca-certificates curl

2.3 Install Docker

Next, install Docker and ensure it starts automatically:

sudo apt install -y docker.io
sudo systemctl enable docker
sudo systemctl start docker

2.4 Install Kubernetes Components

Add the Kubernetes repository and install the core tools:

curl -fsSL https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo gpg --dearmor -o /usr/share/keyrings/kubernetes-archive-keyring.gpg
echo "deb [signed-by=/usr/share/keyrings/kubernetes-archive-keyring.gpg] https://apt.kubernetes.io/ kubernetes-xenial main" | sudo tee /etc/apt/sources.list.d/kubernetes.list
sudo apt update
sudo apt install -y kubelet kubeadm kubectl
sudo systemctl enable kubelet

2.5 Disable Swap

Kubernetes doesn’t work well with swap enabled, so disable it:

sudo swapoff -a
sudo sed -i '/ swap / s/^/#/' /etc/fstab

2.6 Enable Kernel Modules for Networking

Configure the kernel to support Kubernetes networking:

sudo modprobe br_netfilter
echo 'br_netfilter' | sudo tee /etc/modules-load.d/br_netfilter.conf

Set up sysctl settings:

cat <<EOF | sudo tee /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-iptables = 1
net.bridge.bridge-nf-call-ip6tables = 1
net.ipv4.ip_forward = 1
EOF

Apply the changes:

sudo sysctl --system

Repeat all of Step 2 on every node.

Step 3: Initialize the Control Plane

Now, let’s set up the control plane. Run this only on the k8s-control-plane node:

sudo kubeadm init --pod-network-cidr=192.168.0.0/16

This command initializes the control plane and sets up the pod network. Once it finishes, you’ll see a kubeadm join command in the output. Copy it somewhere safe—you’ll need it later to connect the worker nodes.

3.1 Configure kubectl on the Control Plane

Set up kubectl so you can manage the cluster:

mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

Step 4: Install the Calico Network Plugin

To enable pod networking, install the Calico CNI plugin on the control plane:

kubectl apply -f https://docs.projectcalico.org/manifests/calico.yaml

Check that all pods are running:

kubectl get pods -n kube-system

Wait until all pods show a Running status.

Step 5: Join Worker Nodes

Head over to your worker nodes (k8s-worker-1 and k8s-worker-2). Use the kubeadm join command from Step 3. It’ll look something like this:

sudo kubeadm join <control-plane-ip>:6443 --token <token> --discovery-token-ca-cert-hash sha256:<hash>

If you lost the command, regenerate it on the control plane:

kubeadm token create --print-join-command

Run the join command on both worker nodes. Then, back on the control plane, verify that all nodes are connected:

kubectl get nodes

You should see all three nodes in a Ready state.

Step 6: Deploy and Scale an Application

Let’s test the cluster by deploying an Nginx server on cluster:

6.1 Deploy Nginx

Create a deployment:

kubectl create deployment nginx --image=nginx

6.2 Expose Nginx as a NodePort Service

Make Nginx accessible:

kubectl expose deployment nginx --type=NodePort --port=80

6.3 Check Service Details

Find the port Nginx is running on:

kubectl get svc nginx

6.4 Scale Nginx to 5 Pods

Scale the deployment:

kubectl scale deployment nginx --replicas=5
kubectl get pods -o wide

You should see three Nginx pods spread across your worker nodes.

Step 7: Delete a Pod

Simulate a failure by deleting a pod. First, list the pods:

kubectl get pods -o wide

Then delete one:

kubectl delete pod <pod-name>

Kubernetes will automatically spin up a replacement pod to maintain three replicas.

Final Verification

Let’s make sure everything’s working:

• Check the cluster nodes:

  kubectl get nodes
  

• Check running pods:

  kubectl get pods -o wide
  

• Test Nginx by accessing it in your browser: http://<any-node-ip>:<nodeport>

  Replace <nodeport> with the port number from kubectl get svc nginx.

Conclusion

Congratulations! You’ve successfully set up a Kubernetes cluster with one control plane and two worker nodes on AWS. You’ve deployed Nginx, scaled it, and tested pod recovery—all the basics of a working K8s setup. Now you’re ready to explore more advanced features.

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