Add Install guide

README.md

@@ -28,6 +28,24 @@
     | kubelet            | minikube | server-cert                |  356 | 2020-01-10 14:51:39 +0000 UTC | /var/lib/kubelet/pki/kubelet.crt                     | Can be ignored this. |
     +--------------------+----------+----------------------------+------+-------------------------------+------------------------------------------------------+----------------------+
 
+## Install
+
+    # MacOS
+    # Download kubectl check-cert
+    $ curl -L https://github.com/leoh0/kubectl-check-cert/releases/download/v0.0.1/kubectl-check_cert_0.0.1_darwin_amd64.tar.gz | tar zxvf - > kubectl-check_cert
+    # Make the binary executable.
+    $ chmod +x kubectl-check_cert
+    # Move the binary in to your PATH.
+    $ sudo mv ./kubectl-check_cert /usr/local/bin/kubectl-check_cert
+
+    # Linux
+    # Download kubectl check-cert
+    $ curl -L https://github.com/leoh0/kubectl-check-cert/releases/download/v0.0.1/kubectl-check_cert_0.0.1_linux_amd64.tar.gz | tar zxvf - > kubectl-check_cert
+    # Make the binary executable.
+    $ chmod +x kubectl-check_cert
+    # Move the binary in to your PATH.
+    $ sudo mv ./kubectl-check_cert /usr/local/bin/kubectl-check_cert
+
 ## Explain certification types
 
 ### Apiserver

cmd/check_cert.go

@@ -248,19 +248,19 @@ func (o *ExpirationOptions) Run(cmd *cobra.Command) error {
 	apiServerPods, err := getPods(
 		coreclient, kubesystemNamespace, "component=kube-apiserver,tier=control-plane")
 	if err != nil {
-		return err
+		fmt.Println("Apiserver is not exists. Skip.")
 	}
 
 	controllerManagerPods, err := getPods(
 		coreclient, kubesystemNamespace, "component=kube-controller-manager,tier=control-plane")
 	if err != nil {
-		return err
+		fmt.Println("ControllerManager is not exists. Skip.")
 	}
 
 	schedulerManagerPods, err := getPods(
 		coreclient, kubesystemNamespace, "component=kube-scheduler,tier=control-plane")
 	if err != nil {
-		return err
+		fmt.Println("Scheduler is not exists. Skip.")
 	}
 
 	dsPodCount := 0