因版本原因replicas=3不能用

#命令格式: kubectl run deployment名称[参数]
#--image指定pod的镜像
#--port指定端口
# --replicas指定创建pod数量
#--namespace指定namespace
[ root@master ~]# kubectl run nginx --image=nginx:1.17.1 --port=80 --replicas=3 -n dev
deployment.apps/nginx created

是因为在K8S v1.18.0以后，–replicas已弃用 ,推荐用 deployment  创建 pods

vim nginx-deployment.yaml

apiVersion: apps/v1
kind: Deployment
metadata:
  name: nginx
  namespace: policy-demo
  labels:
    app: nginx
spec:
  replicas: 2
  selector:
    matchLabels:
      app: nginx
  template:
    metadata:
      labels:
        app: nginx
    spec:
      containers:
      - name: nginx
        image: nginx
        ports:
        - containerPort: 80 

kubectl apply -f nginx-deployment.yaml

[root@master ~]# kubectl get pod,deployment -n dev -o wide
NAME                         READY   STATUS    RESTARTS   AGE   IP            NODE    NOMINATED NODE   READINESS GATES
pod/nginx-7848d4b86f-96vsj   1/1     Running   0          84s   10.244.1.6    node3   <none>           <none>
pod/nginx-7848d4b86f-l6872   1/1     Running   0          84s   10.244.2.10   node2   <none>           <none>

NAME                    READY   UP-TO-DATE   AVAILABLE   AGE   CONTAINERS   IMAGES   SELECTOR
deployment.apps/nginx   2/2     2            2           85s   nginx        nginx    app=nginx