Installing Kubernetes with kubeadm

Install container runtime

# Install containerd (the container runtime Kubernetes uses):
sudo apt update
sudo apt install -y containerd

# Generate default containerd config:
sudo mkdir -p /etc/containerd
containerd config default | sudo tee /etc/containerd/config.toml

# Enable systemd cgroup driver (required for kubeadm):
sudo sed -i 's/SystemdCgroup = false/SystemdCgroup = true/' /etc/containerd/config.toml

sudo systemctl restart containerd
sudo systemctl enable containerd

Install kubeadm, kubelet, kubectl

# Add Kubernetes apt repository:
sudo apt install -y apt-transport-https ca-certificates curl gpg
curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.29/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:/v1.29/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    # Prevent accidental upgrades

# Verify versions:
kubeadm version
kubectl version --client

Initialize the control plane

⚠️ WARNING: Run kubeadm init only on the designated control plane node. Running it on a worker node will turn that node into an unintended control plane.

# On the CONTROL PLANE node only:
sudo kubeadm init --pod-network-cidr=10.244.0.0/16

kubeadm init output (end)

Your Kubernetes control-plane has initialized successfully!

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

You can now join any number of worker nodes by running:
kubeadm join 192.168.1.100:6443 --token abc123.xyz789     --discovery-token-ca-cert-hash sha256:1234abcd...

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

# Install Flannel CNI (Container Network Interface — pods cannot communicate without this):
kubectl apply -f https://raw.githubusercontent.com/flannel-io/flannel/master/Documentation/kube-flannel.yml

# Wait for the control plane node to become Ready:
kubectl get nodes -w    # Watch until STATUS shows Ready

Join worker nodes

# On each WORKER node, run the join command from kubeadm init output:
sudo kubeadm join 192.168.1.100:6443 --token abc123.xyz789     --discovery-token-ca-cert-hash sha256:1234abcd...

# If the token expired (tokens expire after 24h), generate a new one on control plane:
kubeadm token create --print-join-command

# Back on control plane — verify all nodes are Ready:
kubectl get nodes

kubectl get nodes output after joining workers

NAME            STATUS   ROLES           AGE     VERSION
k8s-master      Ready    control-plane   15m     v1.29.2
k8s-worker-01   Ready              3m      v1.29.2

Conclusion

The kubeadm installation sequence always follows the same order: disable swap on all nodes, install containerd with systemd cgroup driver, install kubeadm/kubelet/kubectl, run kubeadm init on the control plane, install a CNI plugin (Flannel or Calico), then join workers with the printed token. The most common failure point is forgetting to install the CNI plugin — without it, pods stay in Pending state and nodes show NotReady because inter-pod networking is broken.