k8s-node-env.sh

#!/usr/bin/env bash
# Script to configure a Kubeadm cluster on Ubuntu machine

set -eu

version_regex='^[0-9]+\.[0-9]+\.[0-9]+$'
KERNEL_VERSION="5.8.1"
K8S_VERSION="1.19.0"
START_TIME=$(date +"%T")

kernel_ppa_host="kernel.ubuntu.com"
kernel_ppa_index="/~kernel-ppa/mainline/"
kernel_dir="/tmp/kubeadm-${START_TIME}/kernel/"


function validate_permissions() {
  if ! [[ $EUID -eq 0 ]]; then
    echo "ERROR: Script is required to run as root"
    exit 1
fi
}

function usage() {
  echo "Usage: $0 [ -k KERNEL_VERSION ] [ -v KUBERNETES_VERSION ]" 1>&2 
  echo "For example use the script as - $0 -v 1.19.0 -k 5.8.1"
}

function exit_usage() {
  usage
  exit 1
}

function parse_opts() {
  while getopts :v:k: flag
  do
    case "${flag}" in
      v)
        K8S_VERSION=${OPTARG}
        ;;
      k)
        KERNEL_VERSION=${OPTARG}
        ;;
      :)
        echo "Error: -${OPTARG} requires an argument."
        exit_usage
        ;;
      *)
        exit_usage
        ;;
    esac
  done

  if [[ $K8S_VERSION =~ $version_regex ]]; then
    echo "INFO: Kuberentes Version:  ${K8S_VERSION}"
  else
    echo "ERROR: Invalid Kubernetes version: '${K8S_VERSION}'"
    exit 1
  fi

  echo "INFO: Kernel Version:  ${KERNEL_VERSION}"
}

function set_req_sysconfig() {
  echo "INFO: Setting required system config"
  sysctl -w net.ipv6.conf.all.forwarding=1
}

function set_req_repositories() {
  echo "INFO: Setting required apt repositories"
  apt update
  curl -s https://packages.cloud.google.com/apt/doc/apt-key.gpg | apt-key add -
  cat <<EOF >/etc/apt/sources.list.d/kubernetes.list
deb http://apt.kubernetes.io/ kubernetes-xenial main
EOF
  apt update
}

function setup_download_utils() {
  apt install curl apt-transport-https -y
}

function download_initramfs_tools() {
  apt update && apt install -y initramfs-tools
}

function download_required_kernel() {
  mkdir -p "${kernel_dir}"

  downloads_uri="https://${kernel_ppa_host}${kernel_ppa_index}v${KERNEL_VERSION}/amd64/"

  # Download only generic kernel components from the directory
  # listing
  packages=$(curl -s "${downloads_uri}" | \
    grep -Eoi '<a [^>]+>' | \
    grep -Eo 'href="[^\"]+"' | \
    grep -Eo 'linux[^\"]+' | \
    grep -v 'lowlatency')

  IFS=$'\n'
  for pkg in $packages
  do
    package_uri="${downloads_uri}${pkg}"
    curl -fsSL "${package_uri}" -o "${kernel_dir}/${pkg}"
  done

  download_initramfs_tools
  echo "INFO: Downloaded kernel packages to ${kernel_dir}"
}

function setup_container_runtime() {
  if ! [[ -x "$(command -v docker)" ]]; then
    echo "INFO: Installing Docker as container runtime"
    apt install docker.io -y
  else
    echo "INFO: Docker is already installed"
  fi
}

function setup_k8s_components() {
  setup_container_runtime
  echo "INFO: Installing kubectl on the node"
  apt install -y "kubectl=${K8S_VERSION}-00"

  echo "INFO: Installing kubeadm on the node"
  apt install -y "kubeadm=${K8S_VERSION}-00"

  echo "INFO: Installing kubelet on the node"
  apt install -y "kubelet=${K8S_VERSION}-00"
}

function install_new_kernel() {
  cd "${kernel_dir}" && dpkg -i *.deb

  local kv
  local regex 
  
  regex="${KERNEL_VERSION}-[^\ ]+-generic"
  kv=$(dpkg --list | grep "linux-image" | grep -Eo "${regex}")

  update-initramfs -u -k "${kv}"
  update-grub
}

validate_permissions
parse_opts
set_req_sysconfig
set_req_repositories
download_required_kernel
setup_k8s_components

echo "INFO: Installation of required component finished"

install_new_kernel

read -p "Reboot Machine(Y/N)? :" -n 1 -r
if [[ $REPLY =~ ^[Yy]$ ]]; then
    reboot
fi