kubernetes/cmd/kubeadm/app/phases/upgrade/postupgrade.go

// UnupgradedControlPlaneInstances returns a list of control plane instances that have not yet been upgraded.
//
// NB. This function can only be called after the current control plane instance has been upgraded already.
// Because it determines whether the other control plane instances have been upgraded by checking whether
// the kube-apiserver image of other control plane instance is the same as that of this instance.
func UnupgradedControlPlaneInstances(client clientset.Interface, nodeName string) ([]string, error) { … }

// WriteKubeletConfigFiles writes the kubelet config file to disk, but first creates a backup of any existing one.
func WriteKubeletConfigFiles(cfg *kubeadmapi.InitConfiguration, patchesDir string, dryRun bool, out io.Writer) error { … }

// GetKubeletDir gets the kubelet directory based on whether the user is dry-running this command or not.
func GetKubeletDir(dryRun bool) (string, error) { … }

// UpdateKubeletLocalMode changes the Server URL in the kubelets kubeconfig to the local API endpoint if it is currently
// set to the ControlPlaneEndpoint.
// TODO: remove this function once kubeletKubeConfigFilePath goes GA and is hardcoded to enabled by default:
// https://github.com/kubernetes/kubeadm/issues/2271
func UpdateKubeletLocalMode(cfg *kubeadmapi.InitConfiguration, dryRun bool) error { … }