Remove the default clustername, and make it optional in api

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

@@ -191,6 +191,7 @@ func SetDefaults_NodeConfiguration(obj *NodeConfiguration) {
 		obj.DiscoveryTimeout = &metav1.Duration{
 			Duration: DefaultDiscoveryTimeout,
 		}
+	}
 	if obj.ClusterName == "" {
 		obj.ClusterName = DefaultClusterName
 	}

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

@@ -118,7 +118,7 @@ type MasterConfiguration struct {
 	FeatureGates map[string]bool `json:"featureGates,omitempty"`
 
 	// The cluster name
-	ClusterName string `json:"clusterName"`
+	ClusterName string `json:"clusterName,omitempty"`
 }
 
 // API struct contains elements of API server address.
@@ -230,7 +230,7 @@ type NodeConfiguration struct {
 	// CRISocket is used to retrieve container runtime info.
 	CRISocket string `json:"criSocket,omitempty"`
 	// ClusterName is the name for the cluster in kubeconfig.
-	ClusterName string `json:"clusterName"`
+	ClusterName string `json:"clusterName,omitempty"`
 
 	// DiscoveryTokenCACertHashes specifies a set of public key pins to verify
 	// when token-based discovery is used. The root CA found during discovery

cmd/kubeadm/app/cmd/init.go

@@ -108,7 +108,7 @@ var (
 
 // NewCmdInit returns "kubeadm init" command.
 func NewCmdInit(out io.Writer) *cobra.Command {
-	cfg := &kubeadmapiext.MasterConfiguration{ClusterName: "kubernetes"}
+	cfg := &kubeadmapiext.MasterConfiguration{}
 	legacyscheme.Scheme.Default(cfg)
 
 	var cfgPath string

cmd/kubeadm/app/cmd/join.go

@@ -102,7 +102,7 @@ var (
 
 // NewCmdJoin returns "kubeadm join" command.
 func NewCmdJoin(out io.Writer) *cobra.Command {
-	cfg := &kubeadmapiext.NodeConfiguration{ClusterName: "kubernetes"}
+	cfg := &kubeadmapiext.NodeConfiguration{}
 	legacyscheme.Scheme.Default(cfg)
 
 	var skipPreFlight bool