ReplicaSet和ReplicationController

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前文提及kubectl根据pod yml启动pod，接下来我们删除pod

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kubectl delete -f pod_nginx.yml

查看运行pod

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kubectl get pods

编写yml，实例类型为ReplicationController

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apiVersion: v1
kind: ReplicationController 
metadata:
  name: nginx
spec:
  replicas: 3
  selector:
    app: nginx
  template:
    metadata:
      name: nginx
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80

selector是选择器，告诉Service之间如何发现pod
teplate定义了pod格式
metadata是pod的元信息
spec指定pod内容，containers定义了容器
接下来我们启动ReplicationController

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kubectl create -f rs_nginx.yml

因为我们定义了副本数量为3，所以启动三个pod

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kubectl get rc

查看replicationcontroller，可以看到启动了nginx的controller
同时，我们查看下pods

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kubectl get pods

当我们删除其中一个pod时，controller会重新启动一个pod，保证副本数为三个

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kubectl delete pods nginx-6r92b

再次查看kubectl get pods 查看pod列表，发现pod数量仍为三个
我们也可以扩充副本数量

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kubectl scale rc nginx --replicas=2

同样我们可以通过replicaset 设置启动pod

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apiVersion: apps/v1
kind: ReplicaSet
metadata:
  name: nginx
  labels:
    tier: frontend
spec:
  replicas: 3
  selector:
    matchLabels:
      tier: frontend
  template:
    metadata:
      name: nginx
      labels:
        tier: frontend
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80

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