kubeadm: change the control plane IP

# Check if the correct number of arguments are provided
if [ "$#" -ne 2 ]; then
    echo "Usage: $0 <oldIP> <newIP>"
    exit 1
fi

# Assign the script arguments to variables
oldIP=$1
newIP=$2

echo "Stopping kubelet service"
systemctl stop kubelet

echo "Removing al certificates and *.conf files"
rm -rf /etc/kubernetes/pki/*
rm /var/lib/kubelet/pki/kubelet*
rm /etc/kubernetes/*.conf

echo "Changing IP from $oldIP to $newIP for all static pod manifests"
find /etc/kubernetes -type f | xargs grep $oldIP
find /etc/kubernetes -type f | xargs sed -i "s/$oldIP/$newIP/"

echo "Changing IP from $oldIP to $newIP for kubelet configuration"
find /etc/default/kubelet -type f | xargs sed -i "s/$oldIP/$newIP/"

echo "Stoping all controlplane containers"
crictl stop -t 0 $(crictl ps -aq)

echo "Initializing the controlplane with new IP"
# Keep the updated static pod manifests and etcd data
kubeadm init --control-plane-endpoint $newIP \
    --ignore-preflight-errors=FileAvailable--etc-kubernetes-manifests-kube-apiserver.yaml \
    --ignore-preflight-errors=FileAvailable--etc-kubernetes-manifests-kube-controller-manager.yaml \
    --ignore-preflight-errors=FileAvailable--etc-kubernetes-manifests-kube-scheduler.yaml \
    --ignore-preflight-errors=FileAvailable--etc-kubernetes-manifests-etcd.yaml \
    --ignore-preflight-errors=DirAvailable--var-lib-etcd

echo "Showing the IP present in the new apiserver certificate:"
openssl x509 -in /etc/kubernetes/pki/apiserver.crt -text -noout | grep -A 1 "Subject Alternative Name"

# Wait until the apiserver container is running
while ! crictl ps | grep -q "apiserver"; do
    echo "Waiting for the apiserver container to start..."
    sleep 5
done

export KUBECONFIG=/etc/kubernetes/admin.conf

# Wait until the kubectl command can successfully get the pods
until kubectl get po -A > /dev/null 2>&1; do
    echo "Waiting for the cluster to be ready..."
    sleep 5
done

echo "Restarting all coredns pods"
kubectl --namespace kube-system delete pods --selector k8s-app=kube-dns --force --grace-period=0

echo "Restarting all calico pods (network plugin)"
kubectl --namespace kube-system delete pods --selector k8s-app=calico-kube-controllers --force --grace-period=0

echo "-------------------------------------------------------------"

echo "The new kubectl configuration is:"
echo "/etc/kubernetes/admin.conf" 
echo "-------------------------------------------------------------"
echo "To use the new kubectl configuration, run the following commands:"
echo "mkdir -p $HOME/.kube"
echo "sudo cp -i /etc/kubernetes/admin.conf $HOME/.kube/config"
echo "sudo chown $(id -u):$(id -g) $HOME/.kube/config"

echo "-------------------------------------------------------------"
echo "Done"