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Krisha Arya
Krisha Arya

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Manual Kubernetes Cluster Setup on AWS (kubeadm + Flannel)

#devops #beginners #webdev #tutorial

Introduction

Setting up a Kubernetes cluster manually is the best way to understand how Kubernetes works internally.
In this guide, we set up a 2-node Kubernetes cluster on AWS EC2, where:

  • One instance acts as the Master Node
  • One instance acts as a Worker Node

This documentation is based on real troubleshooting, not just ideal steps. It includes:

  • Correct setup steps
  • Common beginner mistakes
  • Real errors faced during setup
  • Why those errors happened
  • Exact commands used to fix them
  • AWS Security Group configuration
  • Final NGINX deployment and access

By the end, you will have:

  • A working Kubernetes cluster
  • Clear understanding of pod networking
  • Knowledge of CNI (Flannel)
  • Practical exposure to NodePort services

Cluster Components

Component Description
Master Node Kubernetes control plane
Worker Node Runs application pods
Runtime containerd
CNI Flannel (VXLAN)
Exposure NodePort

🔹 STEP A: Create AWS EC2 Instances

Create 2 EC2 instances in AWS.

Instance Details

  • OS: Ubuntu 22.04 / 24.04 LTS
  • Instance Type: t2.medium (minimum)
  • VPC/Subnet: Same for both instances
  • Key Pair: k8s.pem

Instance Names

  • Master Node: master-node
  • Worker Node: worker-node-1

🔹 STEP B: Configure Security Group (IMPORTANT)

Attach the same Security Group to both instances.

Inbound Rules

Type Protocol Port Source
SSH TCP 22 Your IP
Kubernetes API TCP 6443 VPC CIDR
NodePort TCP 30080 0.0.0.0/0

⚠️ Without port 30080 open, NodePort will not work in the browser.

🔹 STEP C: Get Public IPs

After instances start, note:

  • Master Public IP
  • Worker Public IP

Example:

Worker Node Public IP: 65.0.4.177
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🔹 STEP D: Prepare SSH Key on Windows (PowerShell)

Open PowerShell as Administrator in the folder containing k8s.pem.

Fix permission issues (VERY IMPORTANT on Windows) 

icacls k8s.pem /inheritance:r
icacls k8s.pem /grant:r "$($env:USERNAME):(R)"
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This avoids:

  • Bad permissions
  • Permission denied (publickey)

🔹 STEP E: SSH into EC2 Instances

Connect to Master Node 

ssh -i k8s.pem ubuntu@<MASTER_PUBLIC_IP>
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Connect to Worker Node 

ssh -i k8s.pem ubuntu@65.0.4.177
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👉 You are now inside the Linux terminal of your EC2 instance.

🔹 STEP F: Verify Connection

Run on both nodes:

whoami
hostname
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Expected Output 

ubuntu
master-node / worker-node-1
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STEP 1: Set Hostnames & Hosts File

Master Node 

sudo hostnamectl set-hostname master-node
hostname
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Worker Node 

sudo hostnamectl set-hostname worker-node-1
hostname
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Update /etc/hosts on BOTH nodes 

sudo nano /etc/hosts
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Example:

172.31.xx.xx master-node
172.31.yy.yy worker-node-1
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STEP 2: Disable Swap & Enable Kernel Networking

Run on BOTH nodes.

Disable Swap 

sudo swapoff -a
sudo sed -i '/ swap / s/^/#/' /etc/fstab
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Load Required Kernel Modules 

sudo modprobe overlay
sudo modprobe br_netfilter
sudo modprobe vxlan
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Persist Modules 

cat <<EOF | sudo tee /etc/modules-load.d/k8s.conf
overlay
br_netfilter
vxlan
EOF
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Enable sysctl Settings 

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

sudo sysctl --system
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STEP 3: Install containerd Runtime

Run on BOTH nodes.

sudo apt update
sudo apt install -y containerd
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Generate Default Config 

sudo mkdir -p /etc/containerd
containerd config default | sudo tee /etc/containerd/config.toml
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Enable systemd Cgroup 

sudo sed -i 's/SystemdCgroup = false/SystemdCgroup = true/' \
/etc/containerd/config.toml
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Restart & Enable 

sudo systemctl restart containerd
sudo systemctl enable containerd
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STEP 4: Install Kubernetes Components

Run on BOTH nodes.

sudo apt update
sudo apt install -y apt-transport-https ca-certificates curl gpg
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Add Kubernetes Repository 

curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.30/deb/Release.key | \
sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg

echo "deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] \
https://pkgs.k8s.io/core:/stable:/v1.30/deb/ /" | \
sudo tee /etc/apt/sources.list.d/kubernetes.list
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Install Components 

sudo apt update
sudo apt install -y kubelet kubeadm kubectl
sudo apt-mark hold kubelet kubeadm kubectl
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STEP 5: Initialize Master Node 

sudo kubeadm init --pod-network-cidr=10.244.0.0/16
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Note: Above IP is fixed. Use same IP.

STEP 6: Configure kubectl (Master Node) 

mkdir -p $HOME/.kube
sudo cp /etc/kubernetes/admin.conf $HOME/.kube/config
sudo chown $(id -u):$(id -g) $HOME/.kube/config
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STEP 7: Install Flannel CNI

Initial Confusion 

kubectl get pods -n kube-system | grep flannel
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➡️ Output was empty (Flannel does not run in kube-system)

Correct Installation Command 

kubectl apply -f https://raw.githubusercontent.com/flannel-io/flannel/master/Documentation/kube-flannel.yml
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Correct Namespace Check 

kubectl get ds -n kube-flannel
kubectl get pods -n kube-flannel
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❌ Errors Faced & How They Were Fixed

❌ Error 1: Flannel CrashLoopBackOff

Cause

  • br_netfilter not loaded
  • vxlan missing
  • /proc/sys/net/bridge not present

Fix

sudo modprobe br_netfilter
sudo modprobe vxlan
lsmod | egrep 'vxlan|br_netfilter'
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❌ Error 2: sysctl bridge error 

cannot stat /proc/sys/net/bridge/bridge-nf-call-iptables
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Cause

  • br_netfilter not loaded on worker

Fix (Worker Node)

sudo modprobe br_netfilter
sudo sysctl -w net.bridge.bridge-nf-call-iptables=1
sudo sysctl -w net.bridge.bridge-nf-call-ip6tables=1
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Persist Settings

cat <<EOF | sudo tee /etc/sysctl.d/99-kubernetes.conf
net.ipv4.ip_forward = 1
net.bridge.bridge-nf-call-iptables = 1
net.bridge.bridge-nf-call-ip6tables = 1
EOF

sudo sysctl --system
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❌ Error 3: CoreDNS stuck in ContainerCreating

Cause

  • Flannel networking not ready

Fix

kubectl delete pod -n kube-flannel -l app=flannel
kubectl get pods -n kube-flannel
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Once Flannel became Running, CoreDNS automatically turned Running.

STEP 8: Join Worker Node 

sudo kubeadm join <MASTER-IP>:6443 --token <TOKEN> \
--discovery-token-ca-cert-hash sha256:<HASH>
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STEP 9: Validate Cluster 

kubectl get nodes
kubectl get pods -n kube-system
kubectl get pods -n kube-flannel
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All components must be Running.

🚀 Deploy NGINX Application

nginx-deployment.yaml 

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx-deploy
spec:
  replicas: 3
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx:latest
        ports:
        - containerPort: 80
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kubectl apply -f nginx-deployment.yaml
kubectl get pods
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nginx-service.yaml (NodePort) 

apiVersion: v1
kind: Service
metadata:
  name: nginx-service
spec:
  type: NodePort
  selector:
    app: nginx
  ports:
  - port: 80
    targetPort: 80
    nodePort: 30080
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kubectl apply -f nginx-service.yaml
kubectl get svc
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Access Application

From Worker Node 

curl http://localhost:30080
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From Browser 

http://<WORKER_PUBLIC_IP>:30080
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⚠️ Requires AWS Security Group port 30080 open

Conclusion

This setup demonstrated:

  • Kubernetes cluster creation using kubeadm
  • Real CNI networking issues and fixes
  • Importance of kernel modules for Flannel
  • AWS networking & NodePort behavior
  • End-to-end deployment of an application

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