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Kubernetes Lab: Creating a Cluster Using KUBEADM

Overview

This lab will guide you through the process of setting up a Kubernetes cluster using Kubeadm. By the end of this lab, you will have a functional Kubernetes cluster deployed across multiple EC2 instances.

What You'll Learn

  • How to install and configure Kubeadm, Kubelet, and Kubectl on EC2 instances.
  • How to configure and initialize the control plane node.
  • How to join worker nodes to the Kubernetes cluster.
  • How to deploy a basic application (NGINX) on your cluster to verify the setup.

Prerequisites

Before starting this lab, ensure you have the following:

  • 3 EC2 instances running Ubuntu or any supported Linux distribution.
  • Security groups configured to allow traffic into the API server (usually port 6443).
  • Sudo or root access to the instances.

Lab Structure

This lab is divided into the following steps:

  1. Install Kubeadm, Kubelet, and Kubectl
  2. Set up the Control Plane
  3. Join Worker Nodes to the Cluster
  4. Install a Pod Network
  5. Verify the Cluster with a Simple Application

Step 1: Install Kubeadm, Kubelet, and Kubectl

Follow the official Kubernetes installation guide for your environment: Install Kubeadm, Kubelet, and Kubectl

Start by updating your package list:

sudo apt-get update

Install necessary dependencies:

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

Download and add the Kubernetes repository key:

curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.31/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg

Add the Kubernetes repository to your system:

echo 'deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v1.31/deb/ /' | sudo tee /etc/apt/sources.list.d/kubernetes.list

Update package list again:

sudo apt-get update

Install Kubelet, Kubeadm, and Kubectl:

sudo apt-get install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl

Enable Kubelet to start on boot:

sudo systemctl enable --now kubelet

Step 2: Configure Sysctl and Install Containerd

See

Load the br_netfilter kernel module to allow bridge network packets to be passed to iptables.

sudo modprobe br_netfilter

Ensure the br_netfilter module is loaded automatically after a reboot.

echo 'br_netfilter' | sudo tee -a /etc/modules-load.d/k8s.conf

Check if the br_netfilter module is loaded in the kernel.

lsmod | grep br_netfilter

Write sysctl settings to enable iptables for bridge network traffic.

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

Kubernetes requires IP forwarding to be enabled on the nodes. Apply the sysctl parameters:

cat <<EOF | sudo tee /etc/sysctl.d/k8s.conf
net.ipv4.ip_forward = 1
EOF

Apply the sysctl settings without reboot:

sudo sysctl --system

Now, install Containerd, the container runtime:

sudo apt install -y containerd
sudo apt install -y cri-tools

Configure Containerd:

sudo mkdir /etc/containerd
containerd config default

Update the Containerd config file to enable Systemd as the Cgroup driver:

containerd config default | sed 's/SystemdCgroup = false/SystemdCgroup = true/' | sudo tee /etc/containerd/config.toml

Restart Containerd:

sudo systemctl restart containerd

Step 3: Initialize the Control Plane Node

See

Now, initialize the control plane node with the following command:

sudo kubeadm init --apiserver-advertise-address <control-plane-ip> --pod-network-cidr "10.244.0.0/16" --upload-certs

This will output a kubeadm join command, which you'll use to join worker nodes to the cluster.

Step 4: Join Worker Nodes to the Cluster

On each worker node, run the join command provided by the control plane node:

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

Step 5: Install a Pod Network

Install a pod network to enable communication between nodes. For this lab, we'll use Flannel:

kubectl apply -f https://github.com/flannel-io/flannel/releases/latest/download/kube-flannel.yml

Verify that the pods are running correctly:

kubectl get pods -n kube-system

Step 6: Set up Kubeconfig for Local Access

On the control plane node, copy the kubeconfig file to your local machine:

cat ~/.kube/config

Copy all the content of the file into your local ~/.kube/config file. This will allow you to access the cluster from your local machine.

Step 7: Verify the Cluster

Run a simple application to verify your cluster setup. For example, deploy NGINX:

kubectl run nginx --image=nginx

Check the status of your pod:

kubectl get pods

Conclusion

Congratulations! You've successfully created a Kubernetes cluster using Kubeadm. You've also verified the setup by running an NGINX pod. From here, you can start deploying more complex applications and explore other Kubernetes features like services, deployments, and namespaces.