How to Install kubeadm and Set Up a Multi-Node Kubernetes Cluster

Teadmistebaas

kubeadm is the official tool for bootstrapping a standard, full-featured Kubernetes cluster. This guide covers setting up a cluster with one control-plane node and one or more worker nodes across separate VPS instances.

Architecture Overview

Control Plane Node (runs the API server, scheduler, etc.)
Worker Node 1 (runs your actual application Pods)
Worker Node 2 (runs your actual application Pods)

Prerequisites (All Nodes)

Ubuntu 22.04/24.04 VPS, 2 vCPU / 2 GB RAM minimum per node
Unique hostname per node
Private networking between nodes, ideally (see How to Set Up a Site-to-Site VPN Between Two VPS Servers if nodes are on different providers)

Step 1 — Disable Swap (Required on All Nodes)

sudo swapoff -a
sudo sed -i '/swap/d' /etc/fstab

Kubernetes requires swap disabled for predictable resource management.

Step 2 — Install a Container Runtime (All Nodes)

See How to Install Docker Engine on Ubuntu & Debian, then install containerd (Kubernetes' preferred runtime interface):

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

Step 3 — Install kubeadm, kubelet, and kubectl (All Nodes)

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

Check the current stable Kubernetes minor version and adjust the URL accordingly.

Step 4 — Initialize the Control Plane (Control Plane Node Only)

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

Save the kubeadm join command printed at the end — you'll need it for worker nodes.

Step 5 — Configure kubectl Access (Control Plane Node)

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

Step 6 — Install a Pod Network Add-on (Control Plane Node)

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

Flannel is a simple, widely-used network overlay; other options (Calico, Cilium) offer more advanced features if needed later.

Step 7 — Join Worker Nodes to the Cluster

On each worker node, run the exact kubeadm join command saved from Step 4:

sudo kubeadm join CONTROL_PLANE_IP:6443 --token TOKEN --discovery-token-ca-cert-hash sha256:HASH

Step 8 — Verify All Nodes Joined

kubectl get nodes

All nodes should eventually show Ready once the network add-on finishes initializing.

Regenerating the Join Token (If Lost or Expired)

kubeadm token create --print-join-command

Common Errors

"connection refused" during kubeadm init — verify containerd is running (sudo systemctl status containerd) before initializing.

Nodes stuck in "NotReady" — almost always means the pod network add-on hasn't been applied or hasn't finished initializing; verify Step 6 completed successfully.

Worker join fails with a certificate error — the join token likely expired (tokens are valid for 24 hours by default); generate a new one per the command above.

Best Practices

Use k3s instead if you don't specifically need the full upstream distribution — it's considerably simpler to operate
Keep the control plane node's resources dedicated to cluster management, not application workloads, in production setups
Secure the API server port (6443) and restrict access appropriately

Continue Reading

Browse more articles in Kubernetes & Container Orchestration.

Teadmistebaas

Kategooriad

Kategooriad