Setup Kubernetes cluster on Centos9/RHEL9

setup-k8s.sh

#!/bin/bash

# sytem changes related for overlay networking

# add kernel modules
modprobe br_netfilter
modprobe ip_vs
modprobe ip_vs_rr
modprobe ip_vs_wrr
modprobe ip_vs_sh
modprobe overlay

cat << EOF | tee /etc/modules-load.d/k8s-modules.conf
br_netfilter
ip_vs
ip_vs_rr
ip_vs_wrr
ip_vs_sh
overlay
EOF

# enable iptables for v4 & v6, ip forwarding
cat << EOF |  tee /etc/sysctl.d/k8s.conf
net.bridge.bridge-nf-call-ip6tables = 1
net.bridge.bridge-nf-call-iptables = 1
net.ipv4.ip_forward = 1
EOF

sysctl --system

# disable swap
swapoff -a

# install containerd
dnf config-manager --add-repo https://download.docker.com/linux/centos/docker-ce.repo
dnf makecache
dnf -y install containerd.io

# enable systemdcgroup for containerd
mkdir -p /etc/containerd
containerd config default | tee /etc/containerd/config.toml
sed -i "s/SystemdCgroup = false/SystemdCgroup = true/g" /etc/containerd/config.toml

systemctl enable containerd && systemctl restart containerd

# add k8s related repos
cat <<EOF | tee /etc/yum.repos.d/kubernetes.repo
[kubernetes]
name=Kubernetes
baseurl=https://pkgs.k8s.io/core:/stable:/v1.29/rpm/
enabled=1
gpgcheck=1
gpgkey=https://pkgs.k8s.io/core:/stable:/v1.29/rpm/repodata/repomd.xml.key
exclude=kubelet kubeadm kubectl cri-tools kubernetes-cni
EOF

# install k8s packages
dnf makecache; dnf install -y kubelet kubeadm kubectl --disableexcludes=kubernetes

# add socat
dnf install socat

systemctl enable --now kubelet.service

# pull relevant kubeadm images
kubeadm config images pull

# setup cluster
kubeadm init --pod-network-cidr 192.168.0.0/16

# copy config for kubectl
mkdir -p $HOME/.kube
cp -i /etc/kubernetes/admin.conf $HOME/.kube/config
chown $(id -u):$(id -g) $HOME/.kube/config

# setup calico CNI
kubectl apply -f https://docs.projectcalico.org/manifests/calico.yaml

# get joining token for adding workers
# kubeadm token create --print-join-command