Usage: Usage:  kubectl expose TYPE NAME [--port=port] [--protocol=TCP|UDP|SCTP] [--target-port=n] [--name=name] [--external-ip=external-ip-of-service] [options]
Man:    TYPE为deployment,NAME为depoly资源名称，port和target-port分别为集群和pod的端口

[root@hdss7-21 ~]# kubectl expose deployment app-deploy --port=80 --target-port=80 --name=app-svc -n app
[root@hdss7-21 ~]# kubectl describe svc app-svc -n app
Name:              app-svc
Namespace:         app
Labels:            app=app-deploy
Annotations:       <none>
Selector:          app=app-deploy
Type:              ClusterIP
IP:                192.168.28.124
Port:              <unset>  80/TCP
TargetPort:        80/TCP
Endpoints:         172.7.21.8:80