背景：
有时候我们要对一个node节点进行维修，升级，需要重启开关机，那怎么才能做到应用不影响呢？
技术：
我们可以使用 命令操作
kubectl drain <node name>
官方文档：
https://kubernetes.io/docs/tasks/administer-cluster/safely-drain-node/
https://kubernetes.io/docs/reference/generated/kubectl/kubectl-commands#drain
如果想维护期间将节点留在集群中。执行
kubectl uncordon <node name>
子命令
Options:
--delete-local-data=false: Continue even if there are pods using emptyDir (local data that will be deleted when
the node is drained).
--dry-run=false: If true, only print the object that would be sent, without sending it.
--force=false: Continue even if there are pods not managed by a ReplicationController, ReplicaSet, Job, DaemonSet
or StatefulSet.
--grace-period=-1: Period of time in seconds given to each pod to terminate gracefully. If negative, the default
value specified in the pod will be used.
--ignore-daemonsets=false: Ignore DaemonSet-managed pods.
--pod-selector='': Label selector to filter pods on the node
-l, --selector='': Selector (label query) to filter on
--timeout=0s: The length of time to wait before giving up, zero means infinite
Usage:
kubectl drain NODE [options]
注意：如果执行过程中不需要驱逐 DS容器，使用–ignore-daemonsets=false
执行之后会有error报错 ，请忽略
