例如要在集群中移出node2节点
1)在master节点上执行：
kubectl drain node2 --delete-local-data --force --ignore-daemonsets
kubectl delete node node2
2)在node2上执行：
kubeadm reset ifconfig cni0 down ip link delete cni0 ifconfig flannel.1 down ip link delete flannel.1 rm -rf /var/lib/cni/
