Run dashboard with internal kubectl if not in path

If "kubectl" is not in the PATH, then use the same cached binary
as with the "minikube kubectl" command (version matching cluster).

cmd/minikube/cmd/dashboard.go

@@ -63,10 +63,8 @@ var dashboardCmd = &cobra.Command{
 			}
 		}
 
-		kubectl, err := exec.LookPath("kubectl")
-		if err != nil {
-			exit.WithCodeT(exit.NoInput, "kubectl not found in PATH, but is required for the dashboard. Installation guide: https://kubernetes.io/docs/tasks/tools/install-kubectl/")
-		}
+		kubectlVersion := co.Config.KubernetesConfig.KubernetesVersion
+		var err error
 
 		// Check dashboard status before enabling it
 		dashboardAddon := assets.Addons["dashboard"]
@@ -90,7 +88,7 @@ var dashboardCmd = &cobra.Command{
 		}
 
 		out.ErrT(out.Launch, "Launching proxy ...")
-		p, hostPort, err := kubectlProxy(kubectl, cname)
+		p, hostPort, err := kubectlProxy(kubectlVersion, cname)
 		if err != nil {
 			exit.WithError("kubectl proxy", err)
 		}
@@ -124,10 +122,17 @@ var dashboardCmd = &cobra.Command{
 }
 
 // kubectlProxy runs "kubectl proxy", returning host:port
-func kubectlProxy(path string, contextName string) (*exec.Cmd, string, error) {
+func kubectlProxy(kubectlVersion string, contextName string) (*exec.Cmd, string, error) {
 	// port=0 picks a random system port
 
-	cmd := exec.Command(path, "--context", contextName, "proxy", "--port=0")
+	kubectlArgs := []string{"--context", contextName, "proxy", "--port=0"}
+
+	var cmd *exec.Cmd
+	if kubectl, err := exec.LookPath("kubectl"); err == nil {
+		cmd = exec.Command(kubectl, kubectlArgs...)
+	} else if cmd, err = KubectlCommand(kubectlVersion, kubectlArgs...); err != nil {
+		return nil, "", err
+	}
 
 	stdoutPipe, err := cmd.StdoutPipe()
 	if err != nil {

cmd/minikube/cmd/kubectl.go

@@ -43,17 +43,12 @@ minikube kubectl -- get pods --namespace kube-system`,
 		co := mustload.Healthy(ClusterFlagValue())
 
 		version := co.Config.KubernetesConfig.KubernetesVersion
-		if version == "" {
-			version = constants.DefaultKubernetesVersion
-		}
-
-		path, err := node.CacheKubectlBinary(version)
+		c, err := KubectlCommand(version, args...)
 		if err != nil {
 			out.ErrLn("Error caching kubectl: %v", err)
 		}
 
 		glog.Infof("Running %s %v", path, args)
-		c := exec.Command(path, args...)
 		c.Stdin = os.Stdin
 		c.Stdout = os.Stdout
 		c.Stderr = os.Stderr
@@ -70,3 +65,17 @@ minikube kubectl -- get pods --namespace kube-system`,
 		}
 	},
 }
+
+// KubectlCommand will return kubectl command with a version matching the cluster
+func KubectlCommand(version string, args ...string) (*exec.Cmd, error) {
+	if version == "" {
+		version = constants.DefaultKubernetesVersion
+	}
+
+	path, err := node.CacheKubectlBinary(version)
+	if err != nil {
+		return nil, err
+	}
+
+	return exec.Command(path, args...), nil
+}