Uninstall and Remove

Step 1: Remove the Node from the Cluster

1. Mark the Node as Unschedulable

   kubectl cordon kube-worker-3

2. Drain the Node:

   kubectl drain kube-worker-3 --ignore-daemonsets --delete-local-data

3. Delete the Node:

   Remove the node from the Kubernetes cluster:

   kubectl delete node kube-worker-3  

Step 2: Clean Up Flannel and CNI Configurations on the Node

Execute the following steps on the node to clean up Flannel and CNI configurations:

1. Stop and Disable kubelet and containerd Services:

   sudo kubeadm reset
   sudo systemctl stop kubelet
   sudo systemctl stop containerd
   sudo systemctl disable kubelet
   sudo systemctl disable containerd
   sudo apt-get remove kubelet kubeadm kubectl

2. Remove Flannel Configurations and Data:

   sudo rm -rf /var/lib/cni/
   sudo rm -rf /var/lib/kubelet/*
   sudo rm -rf /etc/cni/
   sudo rm -rf /run/flannel/

3. Remove CNI Configurations and Data:

   sudo rm -rf /etc/cni/net.d/
   sudo rm -rf /var/lib/cni/
   # sudo rm -rf /opt/cni/bin/

4. Remove containerd Data:

   sudo rm -rf /var/lib/containerd/
   sudo rm -rf /etc/kubernetes/kubelet.conf 
   sudo rm -rf /etc/kubernetes/pki/ca.crt
   # sudo rm -rf /etc/systemd/system/containerd.service.d/http-proxy.conf
   # sudo rm -rf /etc/kubernetes/bootstrap-kubelet.conf

5. Reboot the Node:

   sudo reboot

6. Verify the Cleanup

   Use the following command to verify that the node has been removed from the Kubernetes cluster:

   kubectl get nodes

7. Verify the Cleanup is Complete:

   sudo ls /var/lib/kubelet
   sudo ls /etc/cni/net.d/
   sudo ls /opt/cni/bin/
   sudo ls /var/lib/containerd/

If these directories do not exist or are empty, the cleanup is complete.

Reset Control Plane

kubeadm reset
sudo rm -rf /etc/cni/net.d/
sudo rm -rf /var/lib/cni/
sudo rm -rf $HOME/.kube/config
sudo reboot