Usage:  kubectl get resource [-o wide|json|yaml] [-n namespace]
Man:    获取资源的相关信息，-n 指定名称空间，-o 指定输出格式
        resource可以是具体资源名称，如pod nginx-xxx；也可以是资源类型，如pod；或者all(仅展示几种核心资源，并不完整)
        -A, --all-namespace 表示显示所有名称空间

[root@hdss7-21 ~]# kubectl get cs
NAME                 STATUS    MESSAGE              ERROR
controller-manager   Healthy   ok                   
scheduler            Healthy   ok                   
etcd-1               Healthy   {"health": "true"}   
etcd-2               Healthy   {"health": "true"}   
etcd-0               Healthy   {"health": "true"} 
[root@hdss7-21 ~]# kubectl get node -o wide
NAME                STATUS   ROLES         AGE   VERSION   INTERNAL-IP   EXTERNAL-IP   OS-IMAGE                KERNEL-VERSION          CONTAINER-RUNTIME
hdss7-21.host.com   Ready    master,node   11d   v1.15.2   10.4.7.21     <none>        CentOS Linux 7 (Core)   3.10.0-862.el7.x86_64   docker://19.3.5
hdss7-22.host.com   Ready    master,node   11d   v1.15.2   10.4.7.22     <none>        CentOS Linux 7 (Core)   3.10.0-862.el7.x86_64   docker://19.3.5
[root@hdss7-21 ~]# kubectl get svc -o wide -n kube-system
NAME                      TYPE        CLUSTER-IP        EXTERNAL-IP   PORT(S)                  AGE     SELECTOR
coredns                   ClusterIP   192.168.0.2       <none>        53/UDP,53/TCP,9153/TCP   4d20h   k8s-app=coredns
kubernetes-dashboard      ClusterIP   192.168.140.139   <none>        443/TCP                  3d9h    k8s-app=kubernetes-dashboard
traefik-ingress-service   ClusterIP   192.168.45.46     <none>        80/TCP,8080/TCP          3d19h   k8s-app=traefik-ingress
[root@hdss7-21 ~]# kubectl get pod nginx-ds-jdp7q -o yaml
apiVersion: v1
kind: Pod
metadata:
  creationTimestamp: "2020-01-13T13:13:02Z"
  generateName: nginx-ds-
  labels:
    app: nginx-ds
......
[root@centos-7-51 ~]# kubectl get pod -A
NAMESPACE              NAME                                        READY   STATUS    RESTARTS   AGE
default                pod-demo                                    1/1     Running   0          23m
kube-system            coredns-7cf6c46dd5-9phnm                    1/1     Running   2          6d1h
kube-system            coredns-7cf6c46dd5-dm55x                    1/1     Running   2          6d1h
kube-system            etcd-centos-7-51                            1/1     Running   2          6d1h
kube-system            etcd-centos-7-52                            1/1     Running   2          6d1h
kube-system            etcd-centos-7-53                            1/1     Running   2          6d1h
kube-system            kube-apiserver-centos-7-51                  1/1     Running   2          6d1h
kube-system            kube-apiserver-centos-7-52                  1/1     Running   2          6d1h
kube-system            kube-apiserver-centos-7-53                  1/1     Running   2          6d1h
kube-system            kube-controller-manager-centos-7-51         1/1     Running   3          6d1h
kube-system            kube-controller-manager-centos-7-52         1/1     Running   3          6d1h
kube-system            kube-controller-manager-centos-7-53         1/1     Running   3          6d1h
kube-system            kube-flannel-ds-c2bs6                       1/1     Running   4          7d12h
kube-system            kube-flannel-ds-t6j77                       1/1     Running   5          7d12h
kube-system            kube-flannel-ds-w526w                       1/1     Running   4          7d12h
kube-system            kube-flannel-ds-wp546                       1/1     Running   5          7d12h
kube-system            kube-flannel-ds-xc5cb                       1/1     Running   3          7d12h
kube-system            kube-proxy-b2dcj                            1/1     Running   4          6d1h
kube-system            kube-proxy-gjhjc                            1/1     Running   4          6d1h
kube-system            kube-proxy-m6xn7                            1/1     Running   4          6d1h
kube-system            kube-proxy-qpndv                            1/1     Running   4          6d1h
kube-system            kube-proxy-tbjz8                            1/1     Running   4          6d1h
kube-system            kube-scheduler-centos-7-51                  1/1     Running   3          6d1h
kube-system            kube-scheduler-centos-7-52                  1/1     Running   3          6d1h
kube-system            kube-scheduler-centos-7-53                  1/1     Running   2          6d1h
kube-system            metrics-server-c66c59557-vbhq4              1/1     Running   2          6d
kube-system            traefik-ingress-controller-2gpfs            1/1     Running   3          7d11h
kube-system            traefik-ingress-controller-8jhgb            1/1     Running   3          7d11h
kubernetes-dashboard   dashboard-metrics-scraper-894c58c65-58ftb   1/1     Running   2          6d20h
kubernetes-dashboard   kubernetes-dashboard-ffb9ffc86-2np2t        1/1     Running   2          6d17h
storage                nfs-client-provisioner-5bdc64dd59-ss8cm     1/1     Running   3          6d