DevOps Classroom notes 04/Oct/2026

Install k8s cluster using Kubeadm

Offical Kubeadm docs

basic configuration

1 Master and 2 worker node ==> 3 VM/EC2 instance

• A compatible Linux host. The Kubernetes project provides generic instructions for Linux distributions based on Debian and Red Hat, and those distributions without a package manager.
• 2 GB or more of RAM per machine (any less will leave little room for your apps).
• 2 CPUs or more for control plane machines. Full network connectivity between all machines in the cluster (public or private network is fine).
• Unique hostname, MAC address, and product_uuid for every node. See here for more details.
• Certain ports are open on your machines. See here for more details.

Components:

1. kubeadm – init, join ,reset, upgrade
2. kubectl – used to comunicate with kubeapi server
3. kubelet – Node agent
4. conatainerd
5. CNI (flannel/calico)

Click here to get Ports and protocols for k8s cluster

sudo apt-get update
# apt-transport-https may be a dummy package; if so, you can skip that package
sudo apt-get install -y apt-transport-https ca-certificates curl gpg

curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.37/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:/v1.37/deb/ /' | sudo tee /etc/apt/sources.list.d/kubernetes.list


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

## Install containerd
sudo apt install containerd -y
sudo mkdir -p /etc/containerd
containerd config default | sudo tee /etc/containerd/config.toml > /dev/null
sudo sed -i 's/SystemdCgroup = false/SystemdCgroup = true/' /etc/containerd/config.toml
sudo systemctl restart containerd

## run before kubeadm run 
sudo systemctl enable --now kubelet

## Disable swap

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

## load kernal models
sudo modprobe overlay
sudo modprobe br_netfilter

# Network configuration
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

sudo sysctl --system

network class

A – 10.0.0.0 b – 172.16.0.0 c – 192.168.0.0

 kubeadm init --pod-network-cidr=10.244.0.0/16

To start using your cluster, you need to run the following as a regular user:

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

Alternatively, if you are the root user, you can run:

  export KUBECONFIG=/etc/kubernetes/admin.conf

You should now deploy a pod network to the cluster.
Run "kubectl apply -f [podnetwork].yaml" with one of the options listed at:
  https://kubernetes.io/docs/concepts/cluster-administration/addons/

Then you can join any number of worker nodes by running the following on each as root:

kubeadm join 172.31.44.4:6443 --token 3r99hw.1r9n7ai2o5obzoy2 \
        --discovery-token-ca-cert-hash sha256:b09c908d76711563c0abcf3e222287578e92f08207cfbf993ce19dec189d2f9f

Run in master node

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

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

Connect to worker node and run same steps execpt kubeadm init

Run kubeadm join cmd

create sample.yaml and insert below yaml file

apiVersion: v1
kind: Pod
metadata:
  name: nginx-app
  labels:
    app: nginx-web
spec:
  containers:
  - name: nginx
    image: nginx
    ports:
    - containerPort: 80
---
apiVersion: v1
kind: Service
metadata:
  name: nginx-svc
spec:
  type: NodePort
  selector:
    app: nginx-web
  ports:
    - port: 80
      targetPort: 80

## Deploy above yaml file
kubectl apply -f sample.yaml

Task:

1. create kubeadm install follow class recording
2. deploy sample app and access with node and port.