Run TryStartKubelet conditionally; replace hard-code with constants.

cmd/kubeadm/app/apis/kubeadm/v1alpha1/defaults.go

@@ -30,6 +30,8 @@ const (
 	DefaultServiceDNSDomain = "cluster.local"
 	// DefaultServicesSubnet defines default service subnet range
 	DefaultServicesSubnet = "10.96.0.0/12"
+	// DefaultClusterDNSIP defines default DNS IP
+	DefaultClusterDNSIP = "10.96.0.10"
 	// DefaultKubernetesVersion defines default kubernetes version
 	DefaultKubernetesVersion = "stable-1.8"
 	// DefaultAPIBindPort defines default API port
@@ -40,6 +42,8 @@ const (
 	DefaultCertificatesDir = "/etc/kubernetes/pki"
 	// DefaultImageRepository defines default image registry
 	DefaultImageRepository = "gcr.io/google_containers"
+	// DefaultManifestsDir defines default manifests directory
+	DefaultManifestsDir = "/etc/kubernetes/manifests"
 
 	// DefaultEtcdDataDir defines default location of etcd where static pods will save data to
 	DefaultEtcdDataDir = "/var/lib/etcd"

cmd/kubeadm/app/cmd/init.go

@@ -267,6 +267,9 @@ func NewInit(cfgPath string, cfg *kubeadmapi.MasterConfiguration, skipPreFlight,
 		if err := preflight.RunInitMasterChecks(utilsexec.New(), cfg, criSocket); err != nil {
 			return nil, err
 		}
+
+		// Try to start the kubelet service in case it's inactive
+		preflight.TryStartKubelet()
 	} else {
 		fmt.Println("[preflight] Skipping pre-flight checks.")
 	}
@@ -348,19 +351,19 @@ func (i *Init) Run(out io.Writer) error {
 	}
 
 	if features.Enabled(i.cfg.FeatureGates, features.DynamicKubeletConfig) {
-		// TODO: flag "--dynamic-config-dir" should be specified in /etc/systemd/system/kubelet.service.d/10-kubeadm.conf
+		// NOTE: flag "--dynamic-config-dir" should be specified in /etc/systemd/system/kubelet.service.d/10-kubeadm.conf
 		kubeletCfg := &kubeadmapi.KubeletConfiguration{
 			BaseConfig: &kubeletconfigv1alpha1.KubeletConfiguration{
-				PodManifestPath: "/etc/kubernetes/manifests",
+				PodManifestPath: kubeadmapiext.DefaultManifestsDir,
 				AllowPrivileged: utilpointer.BoolPtr(true),
-				ClusterDNS:      []string{"10.96.0.10"},
-				ClusterDomain:   "cluster.local",
+				ClusterDNS:      []string{kubeadmapiext.DefaultClusterDNSIP},
+				ClusterDomain:   kubeadmapiext.DefaultServiceDNSDomain,
 				Authorization: kubeletconfigv1alpha1.KubeletAuthorization{
-					Mode: "Webhook",
+					Mode: kubeletconfigv1alpha1.KubeletAuthorizationModeWebhook,
 				},
 				Authentication: kubeletconfigv1alpha1.KubeletAuthentication{
 					X509: kubeletconfigv1alpha1.KubeletX509Authentication{
-						ClientCAFile: "/etc/kubernetes/pki/ca.crt",
+						ClientCAFile: kubeadmapiext.DefaultCACertPath,
 					},
 				},
 				CAdvisorPort: utilpointer.Int32Ptr(0),
@@ -392,12 +395,8 @@ func (i *Init) Run(out io.Writer) error {
 		if err := CreateKubeletBaseConfigMapRBACRules(client, i.cfg.NodeName); err != nil {
 			return fmt.Errorf("error creating kubelet base configmap RBAC rules: %v", err)
 		}
-
 	}
 
-	// Try to start the kubelet service in case it's inactive
-	preflight.TryStartKubelet()
-
 	// waiter holds the apiclient.Waiter implementation of choice, responsible for querying the API server in various ways and waiting for conditions to be fulfilled
 	waiter := getWaiter(i.dryRun, client)
 

cmd/kubeadm/app/cmd/join.go

@@ -212,6 +212,9 @@ func NewJoin(cfgPath string, args []string, cfg *kubeadmapi.NodeConfiguration, s
 		if err := preflight.RunJoinNodeChecks(utilsexec.New(), cfg, criSocket); err != nil {
 			return nil, err
 		}
+
+		// Try to start the kubelet service in case it's inactive
+		preflight.TryStartKubelet()
 	} else {
 		fmt.Println("[preflight] Skipping pre-flight checks.")
 	}
@@ -234,19 +237,15 @@ func (j *Join) Run(out io.Writer) error {
 		return err
 	}
 
-	// Try to start the kubelet service in case it's inactive
-	preflight.TryStartKubelet()
-
 	if features.Enabled(j.cfg.FeatureGates, features.DynamicKubeletConfig) {
-		// TODO: flag "--dynamic-config-dir" should be specified in /etc/systemd/system/kubelet.service.d/10-kubeadm.conf
+		// NOTE: flag "--dynamic-config-dir" should be specified in /etc/systemd/system/kubelet.service.d/10-kubeadm.conf
 		client, err := kubeconfigutil.ClientSetFromFile(kubeadmconstants.GetAdminKubeConfigPath())
 		if err != nil {
 			return err
 		}
 
-		err = cmdutil.UpdateNodeWithConfigMap(client, j.cfg.NodeName)
-		if err != nil {
-			return nil
+		if err = cmdutil.UpdateNodeWithConfigMap(client, j.cfg.NodeName); err != nil {
+			return err
 		}
 	}
 

cmd/kubeadm/app/constants/constants.go

@@ -140,10 +140,12 @@ const (
 	// MasterConfigurationConfigMapKey specifies in what ConfigMap key the master configuration should be stored
 	MasterConfigurationConfigMapKey = "MasterConfiguration"
 
-	// KubeletBaseConfigurationConfigMap specifies in what ConfigMap in the kube-system namespace the init kubelet configuration should be stored
+	// KubeletBaseConfigurationConfigMap specifies in what ConfigMap in the kube-system namespace the initial remote configuration should be stored
 	KubeletBaseConfigurationConfigMap = "kubelet-base-config-1.9"
 
-	// KubeletBaseConfigurationConfigMapKey specifies in what ConfigMap key the init kubelet configuration should be stored
+	// KubeletBaseConfigurationConfigMapKey specifies in what ConfigMap key the initial remote configuration should be stored
+	// TODO: Use the constant ("kubelet.config.k8s.io") defined in pkg/kubelet/kubeletconfig/util/keys/keys.go
+	// after https://github.com/kubernetes/kubernetes/pull/53833 being merged.
 	KubeletBaseConfigurationConfigMapKey = "kubelet"
 
 	// MinExternalEtcdVersion indicates minimum external etcd version which kubeadm supports