kubernetes — tear down the cluster

on master:

for every node do this:

kubectl drain <node name> --delete-local-data --force --ignore-daemonsets
kubectl delete node <node name>

on every node:

kubeadm reset

on master node:

kubeadm reset

To completely uninstall kubernetes:

# on debian base 
sudo apt-get purge kubeadm kubectl kubelet kubernetes-cni kube* 
#on centos base
sudo yum remove kubeadm kubectl kubelet kubernetes-cni kube
*# on debian base
sudo apt-get autoremove
#on centos base
sudo yum autoremove
 
sudo rm -rf ~/.kube

You have to reboot the machine, to get rid of cni interface.