Kubernetes from Scratch: First Steps with a Local Cluster (kubeadm)

Introduction

Kubernetes is the de facto standard for container orchestration in production environments. But before you land on a managed cluster in the cloud (AKS, IKS, GKE), it’s worth understanding how it works from the inside — by building your own cluster from scratch. In this article we’ll set up a fully working K8s cluster using kubeadm on machines running Ubuntu 22.04.

Requirements

You need at least two machines (physical or virtual):

Role	CPU	RAM	Disk	OS
control-plane (master)	2 vCPU	2 GB	20 GB	Ubuntu 22.04
worker-node-1	2 vCPU	2 GB	20 GB	Ubuntu 22.04

Each machine must have a unique hostname and a static IP address. In this example:

master — 192.168.1.10
worker-1 — 192.168.1.11

Step 1 — Prepare All Nodes

Run the following commands on every node (master and worker).

Disable swap

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

Load kernel modules

cat <<EOF | tee /etc/modules-load.d/k8s.conf
overlay
br_netfilter
EOF

modprobe overlay
modprobe br_netfilter

sysctl parameters for Kubernetes

cat <<EOF | 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

sysctl --system

Install containerd

apt update && apt install -y ca-certificates curl gnupg
install -m 0755 -d /etc/apt/keyrings
curl -fsSL https://download.docker.com/linux/ubuntu/gpg | \
  gpg --dearmor -o /etc/apt/keyrings/docker.gpg
chmod a+r /etc/apt/keyrings/docker.gpg

echo "deb [arch=$(dpkg --print-architecture) signed-by=/etc/apt/keyrings/docker.gpg] \
  https://download.docker.com/linux/ubuntu $(. /etc/os-release && echo $VERSION_CODENAME) stable" | \
  tee /etc/apt/sources.list.d/docker.list

apt update && apt install -y containerd.io

containerd config default | tee /etc/containerd/config.toml
sed -i 's/SystemdCgroup = false/SystemdCgroup = true/' /etc/containerd/config.toml
systemctl restart containerd && systemctl enable containerd

Install kubeadm, kubelet, kubectl

curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.29/deb/Release.key | \
  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:/v1.29/deb/ /' | \
  tee /etc/apt/sources.list.d/kubernetes.list

apt update && apt install -y kubelet kubeadm kubectl
apt-mark hold kubelet kubeadm kubectl

Step 2 — Initialise the Master Node

Run only on the master node:

kubeadm init \
  --apiserver-advertise-address=192.168.1.10 \
  --pod-network-cidr=10.244.0.0/16 \
  --control-plane-endpoint=192.168.1.10

Configure kubectl:

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

Step 3 — Install the Network Plugin (CNI)

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

kubectl get nodes
# NAME     STATUS   ROLES           AGE   VERSION
# master   Ready    control-plane   2m    v1.29.0

Step 4 — Join Worker Nodes

Run the kubeadm join command from the initialisation output on each worker node:

kubeadm join 192.168.1.10:6443 --token abc123.xyz \
    --discovery-token-ca-cert-hash sha256:xxxxxxxxxxxxxxxx

If the token has expired, generate a new one:

kubeadm token create --print-join-command

kubectl get nodes -o wide
# NAME       STATUS   ROLES           AGE   VERSION
# master     Ready    control-plane   5m    v1.29.0   192.168.1.10
# worker-1   Ready    <none>          2m    v1.29.0   192.168.1.11

Step 5 — First Application Deployment

kubectl create deployment nginx --image=nginx --replicas=2
kubectl expose deployment nginx --port=80 --type=NodePort
kubectl get pods -o wide
kubectl get svc nginx

Output:

NAME    TYPE       CLUSTER-IP      EXTERNAL-IP   PORT(S)        AGE
nginx   NodePort   10.96.145.200   <none>        80:31234/TCP   30s

Application available at: http://192.168.1.11:31234

Useful Everyday Commands

kubectl cluster-info
kubectl get nodes -o wide
kubectl get pods --all-namespaces
kubectl describe node worker-1
kubectl logs <pod-name> -f
kubectl exec -it <pod-name> -- /bin/bash
kubectl delete deployment nginx

Summary

You have a working Kubernetes cluster with one master and one worker. This is a solid foundation for learning — you can now practise deployments, scaling, ConfigMaps, Secrets and Services. In the next article we’ll show how to install Helm and deploy the first application using charts.