Write marshalled kubeletconfig object to init-config-dir

cmd/kubeadm/app/constants/constants.go

@@ -155,6 +155,14 @@ const (
 	// after https://github.com/kubernetes/kubernetes/pull/53833 being merged.
 	KubeletBaseConfigurationConfigMapKey = "kubelet"
 
+	// KubeletBaseConfigurationDir specifies the directory on the node where stores the initial remote configuration of kubelet
+	KubeletBaseConfigurationDir = "/var/lib/kubelet/config/init"
+
+	// KubeletBaseConfigurationFile specifies the file name on the node which stores initial remote configuration of kubelet
+	// 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.
+	KubeletBaseConfigurationFile = "kubelet"
+
 	// MinExternalEtcdVersion indicates minimum external etcd version which kubeadm supports
 	MinExternalEtcdVersion = "3.0.14"
 

cmd/kubeadm/app/phases/kubelet/kubelet.go

@@ -19,6 +19,10 @@ package kubelet
 import (
 	"encoding/json"
 	"fmt"
+	"io/ioutil"
+	"path/filepath"
+
+	"github.com/ghodss/yaml"
 
 	"k8s.io/api/core/v1"
 	rbac "k8s.io/api/rbac/v1"
@@ -92,6 +96,15 @@ func UpdateNodeWithConfigMap(client clientset.Interface, nodeName string) error
 			return false, nil
 		}
 
+		baseCongfig, err := yaml.Marshal(kubeletCfg.Data[kubeadmconstants.KubeletBaseConfigurationConfigMapKey])
+		if err != nil {
+			return false, err
+		}
+		baseCongfigFile := filepath.Join(kubeadmconstants.KubeletBaseConfigurationDir, kubeadmconstants.KubeletBaseConfigurationFile)
+		if err := ioutil.WriteFile(baseCongfigFile, baseCongfig, 0644); err != nil {
+			return false, fmt.Errorf("failed to write initial remote configuration of kubelet into file %q for node %s: %v", baseCongfigFile, nodeName, err)
+		}
+
 		node.Spec.ConfigSource = &v1.NodeConfigSource{
 			ConfigMapRef: &v1.ObjectReference{
 				Name:      kubeadmconstants.KubeletBaseConfigurationConfigMap,