Deploying a K8s cluster using kubeadm

README.md

Deploying a K8s cluster using kubeadm

1. The nodes-bootstrap.sh script will help you create three multipass virtual machines named k8s-control, k8s-worker-1, and k8s-worker-2 for further cluster deployment.

2. Initialize the control panel on the k8s-control node

   multipass shell k8s-control
   
   CONTROL_IP=$(hostname -I | awk ‘{print $1}’)
   
   sudo kubeadm init \
      --pod-network-cidr=10.244.0.0/16 \
      --apiserver-advertise-address=$CONTROL_IP

3. Configure kubectl on the control panel node

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

4. Install Flannel on the control plane (to create a Pod network)

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

5. Join the worker nodes.

   for NODE in k8s-worker-1 k8s-worker-2; do
      multipass exec $NODE -- sudo kubeadm join 192.168.2.26:6443 \
        --token bsw6fd.e7624wl2688fybjx \
        --discovery-token-ca-cert-hash sha256:7850aa1c6181277e284a08b81256979db25698a89982f0885540376a5376e0bd
    done

Warning

In your case, the IP, token, and hash will be different! Use the command you got from kubeadm init.

6. Log back into the control panel node and check the connection of the worker nodes to the cluster

   multipass shell k8s-control
   kubectl get nodes

   You should see three nodes with the status Ready:

   NAME            STATUS   ROLES           AGE   VERSION
   k8s-control     Ready    control-plane   5m    v1.34.0
   k8s-worker-1    Ready    <none>          2m    v1.34.0
   k8s-worker-2    Ready    <none>          2m    v1.34.0

If the status is NotReady, wait a minute — Flannel is still configuring ⏳

nodes-bootstrap.sh

#!/usr/bin/env bash

# List of nodes
NODES=(k8s-control k8s-worker-1 k8s-worker-2)

echo "=== Starting to prepare all Kubernetes nodes ==="

###############################################################################
# 1. SYSTEM UPDATE
###############################################################################
echo "=== [1/7] System update on all nodes ==="
for NODE in "${NODES[@]}"; do
  multipass exec $NODE -- bash -c "
    sudo apt-get update &&
    sudo apt-get upgrade -y
  "
done

###############################################################################
# 2. DISABLING THE FIREWALL (simplified configuration)
###############################################################################
echo "=== [2/7] Disabling the firewall on all nodes ==="
for NODE in "${NODES[@]}"; do
  multipass exec $NODE -- sudo ufw disable
done

###############################################################################
# 3. LOADING THE NECESSARY KERNEL MODULES
###############################################################################
echo "=== [3/7] Configuring kernel modules ==="
for NODE in "${NODES[@]}"; do
  multipass exec $NODE -- bash -c "
    echo -e 'overlay\nbr_netfilter' | sudo tee /etc/modules-load.d/k8s.conf
    sudo modprobe overlay
    sudo modprobe br_netfilter
  "
done

###############################################################################
# 4. CONFIGURING Network Settings
###############################################################################
echo "=== [4/7] Configuring sysctl parameters ==="
for NODE in "${NODES[@]}"; do
  multipass exec $NODE -- bash -c "
    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
  "
done

###############################################################################
# 5. INSTALLING containerd
###############################################################################
echo "=== [5/7] Installing containerd ==="
for NODE in "${NODES[@]}"; do
  multipass exec $NODE -- sudo apt-get install -y containerd
done

###############################################################################
# 6. CONFIGURATION containerd, SystemdCgroup, and CRICTL
###############################################################################
echo "=== [6/7] Configuring containerd and CRI ==="
for NODE in "${NODES[@]}"; do
  multipass exec $NODE -- bash -c "
    sudo mkdir -p /etc/containerd
    containerd config default | sudo tee /etc/containerd/config.toml

    # Updating sandbox image
    sudo sed -i 's/registry.k8s.io\\/pause:3.8/registry.k8s.io\\/pause:3.10.1/' /etc/containerd/config.toml

    # Enabling cgroup mode via systemd
    sudo sed -i 's/SystemdCgroup = false/SystemdCgroup = true/' /etc/containerd/config.toml

    # Adding config for crictl
    sudo tee /etc/crictl.yaml <<EOF
runtime-endpoint: unix:///run/containerd/containerd.sock
image-endpoint: unix:///run/containerd/containerd.sock
timeout: 10
debug: false
EOF

    sudo systemctl restart containerd
    sudo systemctl enable containerd
  "
done

###############################################################################
# 7. INSTALLATION kubeadm, kubelet, kubectl
###############################################################################
echo "=== [7/7] Встановлення Kubernetes компонентів ==="
for NODE in "${NODES[@]}"; do
  multipass exec $NODE -- bash -c "
    sudo apt-get install -y apt-transport-https ca-certificates curl gpg

    curl -fsSL https://pkgs.k8s.io/core:/stable:/v1.34/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:/v1.34/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
    sudo systemctl enable kubelet
  "
done

###############################################################################
# 8. CONFIRMATION OF READINESS
###############################################################################
echo "=== All nodes are ready! ==="
echo “You can proceed to initialize the control plane.”