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Chapter 3: Setting Up a Kubernetes Cluster

3.1 Cluster Configuration

We'll be setting up a Kubernetes cluster with the following nodes:

  • Master: 172.31.60.117
  • Worker 1: 172.31.60.118
  • Worker 2: 172.31.60.119

3.2 Prerequisites

Ensure all nodes meet these requirements:

  • Ubuntu 20.04 LTS or later
  • At least 2 CPU cores
  • At least 2GB RAM
  • Unique hostname, MAC address, and product_uuid for every node
  • Certain ports are open (we'll cover this in the firewall setup)

3.3 Initial Setup (All Nodes)

Run these commands on all nodes:

# Update the system
sudo apt update && sudo apt upgrade -y

# Install necessary packages
sudo apt install -y apt-transport-https ca-certificates curl software-properties-common

# Add Kubernetes apt repository
curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | sudo apt-key add -
echo "deb https://apt.kubernetes.io/ kubernetes-xenial main" | sudo tee /etc/apt/sources.list.d/kubernetes.list

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

# Hold these packages at their current version
sudo apt-mark hold kubelet kubeadm kubectl

# Disable swap
sudo swapoff -a
sudo sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab

# Load necessary modules
sudo modprobe overlay
sudo modprobe br_netfilter

# Set up required sysctl params
sudo tee /etc/sysctl.d/kubernetes.conf<<EOF
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
net.ipv4.ip_forward = 1
EOF

# Reload sysctl
sudo sysctl --system

# Install containerd
sudo apt install -y containerd
sudo mkdir -p /etc/containerd
containerd config default | sudo tee /etc/containerd/config.toml
sudo systemctl restart containerd
sudo systemctl enable containerd

3.4 Initialize the Master Node

On the master node (172.31.60.117), run:

# Initialize the cluster
sudo kubeadm init --pod-network-cidr=10.244.0.0/16 --apiserver-advertise-address=172.31.60.117

# Set up kubectl for the current user
mkdir -p $HOME/.kube
sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config

# Install a pod network add-on (we'll use Flannel in this example)
kubectl apply -f https://raw.githubusercontent.com/coreos/flannel/master/Documentation/kube-flannel.yml

Save the kubeadm join command that is output after initialization. You'll need this to join worker nodes to the cluster.

3.5 Join Worker Nodes

On both worker nodes (172.31.60.118 and 172.31.60.119), run the kubeadm join command you saved from the previous step. It will look something like this:

sudo kubeadm join 172.31.60.117:6443 --token <token> --discovery-token-ca-cert-hash sha256:<hash>

3.6 Verify Cluster Setup

On the master node, run:

kubectl get nodes

You should see all three nodes listed and in the 'Ready' state.

3.7 Configure Firewall (if needed)

If you're using a firewall, ensure these ports are open:

Master node:

  • TCP 6443: Kubernetes API server
  • TCP 2379-2380: etcd server client API
  • TCP 10250: Kubelet API
  • TCP 10251: kube-scheduler
  • TCP 10252: kube-controller-manager

Worker nodes:

  • TCP 10250: Kubelet API
  • TCP 30000-32767: NodePort Services

3.8 Post-Installation Steps

  1. Set up dashboard (optional):

    kubectl apply -f https://raw.githubusercontent.com/kubernetes/dashboard/v2.5.0/aio/deploy/recommended.yaml

  2. Create a sample deployment:

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

  3. Verify the deployment:

    kubectl get pods
kubectl get services

Congratulations! You now have a functioning Kubernetes cluster.