Init & setup script for k8s clusters

k8s

#!/bin/bash

set -e

MODE=$1

if [ -z "$MODE" ]; then
  echo "Usage: $0 {configure|init|reset}"
  exit 1
fi

check_prerequisites() {
  echo "[~] Checking system requirements..."
  MISSING=0
  
  for bin in curl tar modprobe iptables; do
    if ! command -v $bin &>/dev/null; then
      echo "[!] Missing required binary: $bin"
      MISSING=1
    fi
  done

  if [ ! -f /etc/os-release ]; then
    echo "[!] Missing /etc/os-release, cannot verify OS"
    MISSING=1
  fi

  if [ "$MISSING" -eq 1 ]; then
    echo "[!] One or more critical components are missing. Exiting."
    exit 1
  fi
}

configure_node() {
  check_prerequisites
  echo "[+] Configuring node..."

  read -p "Set hostname: " HOSTNAME
  current_hostname=$(hostname)
  if [ "$HOSTNAME" != "$current_hostname" ]; then
    hostnamectl set-hostname "$HOSTNAME"
  fi

  echo "[+] Disabling SELinux and swap..."
  if selinuxenabled; then setenforce 0 || true; fi
  grep -q '^SELINUX=disabled' /etc/selinux/config || sed -i 's/^SELINUX=.*/SELINUX=disabled/' /etc/selinux/config
  swapoff -a
  grep -q '^#.*swap' /etc/fstab || sed -i '/\sswap\s/s/^/#/' /etc/fstab

  echo "[+] Kernel modules and sysctl setup..."
  modules=(overlay br_netfilter ip_vs ip_vs_rr ip_vs_wrr ip_vs_sh nf_conntrack)
  for m in "${modules[@]}"; do
    lsmod | grep -q "^$m" || modprobe $m || echo "[!] Failed to load module: $m"
  done

  cat <<EOF | tee /etc/modules-load.d/k8s.conf > /dev/null
${modules[@]}
EOF

  SYSCTL_FILE=/etc/sysctl.d/k8s.conf
  grep -q 'net.bridge.bridge-nf-call-iptables' $SYSCTL_FILE 2>/dev/null || cat <<EOF | tee $SYSCTL_FILE
net.bridge.bridge-nf-call-iptables=1
net.bridge.bridge-nf-call-ip6tables=1
net.ipv4.ip_forward=1
net.ipv6.conf.all.forwarding=1
EOF

  sysctl --system

  echo "[+] Installing containerd..."
  if ! command -v containerd &>/dev/null; then
    curl -LO https://github.com/containerd/containerd/releases/download/v1.7.18/containerd-1.7.18-linux-amd64.tar.gz
    tar -C /usr/local -xzf containerd-1.7.18-linux-amd64.tar.gz
    curl -Lo /usr/local/lib/systemd/system/containerd.service https://raw.githubusercontent.com/containerd/containerd/main/containerd.service
    systemctl daemon-reload
    systemctl enable --now containerd
  fi

  mkdir -p /etc/containerd
  grep -q 'pause:3.9' /etc/containerd/config.toml 2>/dev/null || {
    containerd config default > /etc/containerd/config.toml
    sed -i 's|sandbox_image = ".*"|sandbox_image = "registry.k8s.io/pause:3.9"|' /etc/containerd/config.toml
    systemctl restart containerd
  }

  echo "[+] Installing runc and CNI plugins..."
  if ! command -v runc &>/dev/null; then
    curl -Lo /usr/local/sbin/runc https://github.com/opencontainers/runc/releases/download/v1.1.13/runc.amd64
    chmod +x /usr/local/sbin/runc
  fi

  if [ ! -d /opt/cni/bin ]; then
    curl -LO https://github.com/containernetworking/plugins/releases/download/v1.5.1/cni-plugins-linux-amd64-v1.5.1.tgz
    mkdir -p /opt/cni/bin
    tar -C /opt/cni/bin -xzf cni-plugins-linux-amd64-v1.5.1.tgz
  fi

  echo "[+] Installing kubeadm, kubelet, kubectl..."
  if ! command -v kubeadm &>/dev/null; then
    cat <<EOF | tee /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://pkgs.k8s.io/core:/stable:/v1.30/rpm/
enabled=1
gpgcheck=1
gpgkey=https://pkgs.k8s.io/core:/stable:/v1.30/rpm/repodata/repomd.xml.key
exclude=kubelet kubeadm kubectl cri-tools kubernetes-cni
EOF
    yum install -y kubelet kubeadm kubectl --disableexcludes=kubernetes
    systemctl enable --now kubelet
  fi
}

init_cluster() {
  echo "[+] Initializing control plane..."
  read -p "Enter API endpoint (e.g. 192.168.1.135:6443): " ENDPOINT

  kubeadm config images pull
  kubeadm init --control-plane-endpoint=$ENDPOINT

  echo "[+] Setting up kubeconfig..."
  mkdir -p $HOME/.kube
  cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
  chown $(id -u):$(id -g) $HOME/.kube/config

  echo "[+] Applying Calico manifest..."
  curl -O https://raw.githubusercontent.com/projectcalico/calico/v3.28.0/manifests/calico.yaml
  kubectl apply -f calico.yaml
}

reset_cluster() {
  echo "[+] Resetting cluster..."
  kubeadm reset --force
  ipvsadm --clear || true
  rm -rf /etc/cni/net.d/* /etc/kubernetes /var/lib/etcd /var/lib/kubelet /opt/cni/bin
  ip link | grep cali | awk -F: '{print $2}' | xargs -I{} ip link delete {}
  ip link delete tunl0 || true
  iptables -F
  iptables -X
  systemctl stop kubelet
  echo "[+] Reset complete. Reboot recommended."
}

case "$MODE" in
  configure)
    configure_node
    ;;
  init)
    init_cluster
    ;;
  reset)
    reset_cluster
    ;;
  *)
    echo "Unknown command: $MODE"
    exit 1
    ;;
esac