某些特殊情況下，需要將某些服務固定在一臺宿主機上，K8S也適應這種方式，下面以mongo為例，來看看如何實現的：

kubectl label nodes kube-nodenode=kube-nodekubectl get node-a -l "node=kube-node"

pod或者rc的配置項中新增如下配置：

nodeSelector: 
       node: kube-node4

如mongo啟動的rc檔案

apiVersion: v1
kind: ReplicationController
metadata:
 name: mongo
spec:
 replicas: 1 
 template:
   metadata:
     labels:
       run: mongo
   spec:
     containers:
     - name: mongo
       image: daocloud.io/library/mongo:3.2.4
       ports:
         - containerPort: 27017
       volumeMounts:
         - mountPath: /data/db
           name: mongo
     volumes: [{"name":"mongo","hostPath":{"path":"/root/volumes/mongo"}}]
     nodeSelector: 
       node: kube-node4