Merge pull request #51195 from fabriziopandini/kubeadm-minor-CLI-selfhosting

Automatic merge from submit-queue (batch tested with PRs 50713, 47660, 51198, 51159, 51195)

kubeadm selfhosting CLI improvements

**What this PR does / why we need it**:
This PR implements three small improvements for kubeadm selfhosting CLI:
- `kubeadm phase selfhosting` should be `kubeadm phase self-hosting from-static-pods`
- add `--cert-dir`flag
- add `--config`flag and manage MixedArguments conditions

**Which issue this PR fixes**:
fixes [#397](https://github.com/kubernetes/kubeadm/issues/397) - `kubeadm phase selfhosting` should be `kubeadm phase self-hosting from-static-pods`

**Special notes for your reviewer**:
cc @luxas
cc @jamiehannaford

cmd/kubeadm/app/apis/kubeadm/validation/validation.go

@@ -284,8 +284,8 @@ func ValidateMixedArguments(flag *pflag.FlagSet) error {
 
 	mixedInvalidFlags := []string{}
 	flag.Visit(func(f *pflag.Flag) {
-		if f.Name == "config" || strings.HasPrefix(f.Name, "skip-") || f.Name == "dry-run" {
-			// "--skip-*" flags can be set with --config
+		if f.Name == "config" || strings.HasPrefix(f.Name, "skip-") || f.Name == "dry-run" || f.Name == "kubeconfig" {
+			// "--skip-*" flags or other whitelisted flags can be set with --config
 			return
 		}
 		mixedInvalidFlags = append(mixedInvalidFlags, f.Name)

cmd/kubeadm/app/cmd/phases/selfhosting.go

@@ -21,44 +21,77 @@ import (
 
 	"github.com/spf13/cobra"
 
-	kubeadmapi "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm"
 	kubeadmapiext "k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/v1alpha1"
+	"k8s.io/kubernetes/cmd/kubeadm/app/apis/kubeadm/validation"
 	"k8s.io/kubernetes/cmd/kubeadm/app/features"
 	"k8s.io/kubernetes/cmd/kubeadm/app/phases/selfhosting"
 	kubeadmutil "k8s.io/kubernetes/cmd/kubeadm/app/util"
+	configutil "k8s.io/kubernetes/cmd/kubeadm/app/util/config"
 	kubeconfigutil "k8s.io/kubernetes/cmd/kubeadm/app/util/kubeconfig"
 	"k8s.io/kubernetes/pkg/api"
 )
 
 // NewCmdSelfhosting returns the self-hosting Cobra command
 func NewCmdSelfhosting() *cobra.Command {
-	var kubeConfigFile, featureFlagsString string
-	cfg := &kubeadmapiext.MasterConfiguration{}
 	cmd := &cobra.Command{
 		Use:     "selfhosting",
 		Aliases: []string{"selfhosted"},
 		Short:   "Make a kubeadm cluster self-hosted.",
-		Run: func(cmd *cobra.Command, args []string) {
+		RunE:    subCmdRunE("selfhosting"),
+	}
 
+	cmd.AddCommand(getSelfhostingSubCommand())
+	return cmd
+}
+
+// getSelfhostingSubCommand returns sub commands for Selfhosting phase
+func getSelfhostingSubCommand() *cobra.Command {
+
+	cfg := &kubeadmapiext.MasterConfiguration{}
+	// Default values for the cobra help text
+	api.Scheme.Default(cfg)
+
+	var cfgPath, kubeConfigFile, featureFlagsString string
+
+	// Creates the UX Command
+	cmd := &cobra.Command{
+		Use:     "convert-from-staticpods",
+		Aliases: []string{"from-staticpods"},
+		Short:   "Converts a Static Pod-hosted control plane into a self-hosted one.",
+		Run: func(cmd *cobra.Command, args []string) {
 			var err error
 			if cfg.FeatureFlags, err = features.NewFeatureGate(&features.InitFeatureGates, featureFlagsString); err != nil {
 				kubeadmutil.CheckErr(err)
 			}
 
-			api.Scheme.Default(cfg)
-			internalcfg := &kubeadmapi.MasterConfiguration{}
-			api.Scheme.Convert(cfg, internalcfg, nil)
+			if err := validation.ValidateMixedArguments(cmd.Flags()); err != nil {
+				kubeadmutil.CheckErr(err)
+			}
+
+			// This call returns the ready-to-use configuration based on the configuration file that might or might not exist and the default cfg populated by flags
+			internalcfg, err := configutil.ConfigFileAndDefaultsToInternalConfig(cfgPath, cfg)
+			kubeadmutil.CheckErr(err)
+
+			// Gets the kubernetes client
 			client, err := kubeconfigutil.ClientSetFromFile(kubeConfigFile)
 			kubeadmutil.CheckErr(err)
 
+			// Converts the Static Pod-hosted control plane into a self-hosted one
 			err = selfhosting.CreateSelfHostedControlPlane(internalcfg, client)
 			kubeadmutil.CheckErr(err)
 		},
 	}
 
-	cmd.Flags().StringVar(&kubeConfigFile, "kubeconfig", "/etc/kubernetes/admin.conf", "The KubeConfig file to use for talking to the cluster")
+	// Add flags to the command
+	// flags bound to the configuration object
+	cmd.Flags().StringVar(&cfg.CertificatesDir, "cert-dir", cfg.CertificatesDir, `The path where certificates are stored`)
+	cmd.Flags().StringVar(&cfgPath, "config", cfgPath, "Path to kubeadm config file (WARNING: Usage of a configuration file is experimental)")
 	cmd.Flags().StringVar(&featureFlagsString, "feature-gates", featureFlagsString, "A set of key=value pairs that describe feature gates for various features."+
 		"Options are:\n"+strings.Join(features.KnownFeatures(&features.InitFeatureGates), "\n"))
 
+	// flags that are not bound to the configuration object
+	// Note: All flags that are not bound to the cfg object should be whitelisted in cmd/kubeadm/app/apis/kubeadm/validation/validation.go
+	cmd.Flags().StringVar(&kubeConfigFile, "kubeconfig", "/etc/kubernetes/admin.conf", "The KubeConfig file to use for talking to the cluster")
+
 	return cmd
 }