Kubeadm kubernetes cluster Ubuntu 24.04

Kubeadm Cluster Scripts

Init

#!/bin/bash
set -eu

k8s_minor_version=1.31

kubeadm_init(){
  sudo apt update && sudo apt upgrade -y
  sudo apt install apt-transport-https curl -y

  sudo apt install containerd -y
  sudo mkdir -p /etc/containerd
  containerd config default | sudo tee /etc/containerd/config.toml > /dev/null
  sudo sed -i 's/SystemdCgroup = false/SystemdCgroup = true/' /etc/containerd/config.toml
  sudo systemctl restart containerd

  curl -fsSL https://pkgs.k8s.io/core:/stable:/v${k8s_minor_version}/deb/Release.key | sudo gpg --dearmor -o /etc/apt/keyrings/kubernetes-apt-keyring.gpg
  echo "deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v${k8s_minor_version}/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

  sudo swapoff -a
  sudo sed -i '/ swap / s/^\(.*\)$/#\1/g' /etc/fstab

  sudo modprobe overlay
  sudo modprobe br_netfilter
  echo -e "br_netfilter\noverlay" | sudo tee /etc/modules-load.d/kubernetes-cni.conf
  lsmod | grep overlay
  lsmod | grep br_netfilter

  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
  echo "export KUBECONFIG=/etc/kubernetes/admin.conf" >> ~/.bashrc
  sudo reboot
}

kubeadm_init

Upgrade node Kubernetes version

#!/bin/bash
set -eu

k8s_minor_version=1.31

update_kubeadm_version(){
  k8s_minor_version=1.31
  k8s_keyring_file="/etc/apt/keyrings/kubernetes-apt-keyring.gpg"
  if [ ! -f "${k8s_keyring_file}" ]; then
    curl -fsSL https://pkgs.k8s.io/core:/stable:/v${k8s_minor_version}/deb/Release.key 2>/dev/null | sudo gpg --dearmor -o ${k8s_keyring_file}
  fi
  echo "deb [signed-by=/etc/apt/keyrings/kubernetes-apt-keyring.gpg] https://pkgs.k8s.io/core:/stable:/v${k8s_minor_version}/deb/ /" | sudo tee /etc/apt/sources.list.d/kubernetes.list
  sudo apt-get update

  sudo apt-mark unhold kubeadm kubectl kubelet && \
  sudo apt-get install -y kubelet=${k8s_minor_version}.* kubeadm=${k8s_minor_version}.* kubectl=${k8s_minor_version}.* && \
  sudo apt-mark hold kubeadm kubectl kubelet && \
  sudo systemctl restart kubelet
  sudo apt-get -y dist-upgrade
  kubeadm version -o short
  echo "Reboot in 10 seconds"; sleep 10
  sudo reboot
}

update_kubeadm_version

Upgrade primary controller

  k8s_patch_version=$(kubeadm version -o short)
  echo "Updating to version ${k8s_patch_version} in 10 seconds."; sleep 10
  sudo kubeadm upgrade plan
  sudo killall -s SIGTERM kube-apiserver # trigger a graceful kube-apiserver shutdown
  sleep 20 # wait a little bit to permit completing in-flight requests
  kubeadm upgrade apply -y ${k8s_patch_version}

Get Worker Join Command - token expires 24h default

sudo kubeadm token create --print-join-command --ttl 1h

Get Controller Join Command (must be ran from existing controller. token expires 2h default)

sudo kubeadm token create --print-join-command --certificate-key $(sudo kubeadm init phase upload-certs --upload-certs | sed -n '3p')