Kubelet Startup - Command Execution

	Run: func(cmd *cobra.Command, args []string) {
			// initial flag parse, since we disable cobra's flag parsing
			if err := cleanFlagSet.Parse(args); err != nil {
				cmd.Usage()
				klog.Fatal(err)
			}

			// check if there are non-flag arguments in the command line
			cmds := cleanFlagSet.Args()
			if len(cmds) > 0 {
				cmd.Usage()
				klog.Fatalf("unknown command: %s", cmds[0])
			}

// ValidateKubeletFlags validates Kubelet's configuration flags and returns an error if they are invalid.
func ValidateKubeletFlags(f *KubeletFlags) error {
	// ensure that nobody sets DynamicConfigDir if the dynamic config feature gate is turned off
	if f.DynamicConfigDir.Provided() && !utilfeature.DefaultFeatureGate.Enabled(features.DynamicKubeletConfig) {
		return fmt.Errorf("the DynamicKubeletConfig feature gate must be enabled in order to use the --dynamic-config-dir flag")
	}
	if f.NodeStatusMaxImages < -1 {
		return fmt.Errorf("invalid configuration: NodeStatusMaxImages (--node-status-max-images) must be -1 or greater")
	}

	unknownLabels := sets.NewString()
	for k := range f.NodeLabels {
		if isKubernetesLabel(k) && !kubeletapis.IsKubeletLabel(k) {
			unknownLabels.Insert(k)
		}
	}
	if len(unknownLabels) > 0 {
		return fmt.Errorf("unknown 'kubernetes.io' or 'k8s.io' labels specified with --node-labels: %v\n--node-labels in the 'kubernetes.io' namespace must begin with an allowed prefix (%s) or be in the specifically allowed set (%s)", unknownLabels.List(), strings.Join(kubeletapis.KubeletLabelNamespaces(), ", "), strings.Join(kubeletapis.KubeletLabels(), ", "))
	}

	return nil
}

// use dynamic kubelet config, if enabled
			var kubeletConfigController *dynamickubeletconfig.Controller
			if dynamicConfigDir := kubeletFlags.DynamicConfigDir.Value(); len(dynamicConfigDir) > 0 {
				var dynamicKubeletConfig *kubeletconfiginternal.KubeletConfiguration
				dynamicKubeletConfig, kubeletConfigController, err = BootstrapKubeletConfigController(dynamicConfigDir,
					func(kc *kubeletconfiginternal.KubeletConfiguration) error {
						// Here, we enforce flag precedence inside the controller, prior to the controller's validation sequence,
						// so that we get a complete validation at the same point where we can decide to reject dynamic config.
						// This fixes the flag-precedence component of issue #63305.
						// See issue #56171 for general details on flag precedence.
						return kubeletConfigFlagPrecedence(kc, args)
					})
				if err != nil {
					klog.Fatal(err)
				}
				// If we should just use our existing, local config, the controller will return a nil config
				if dynamicKubeletConfig != nil {
					kubeletConfig = dynamicKubeletConfig
					// Note: flag precedence was already enforced in the controller, prior to validation,
					// by our above transform function. Now we simply update feature gates from the new config.
					if err := utilfeature.DefaultMutableFeatureGate.SetFromMap(kubeletConfig.FeatureGates); err != nil {
						klog.Fatal(err)
					}
				}
			}

// InitializeTLS checks for a configured TLSCertFile and TLSPrivateKeyFile: if unspecified a new self-signed
// certificate and key file are generated. Returns a configured server.TLSOptions object.
func InitializeTLS(kf *options.KubeletFlags, kc *kubeletconfiginternal.KubeletConfiguration) (*server.TLSOptions, error) {
	if !kc.ServerTLSBootstrap && kc.TLSCertFile == "" && kc.TLSPrivateKeyFile == "" {
		kc.TLSCertFile = path.Join(kf.CertDirectory, "kubelet.crt")
		kc.TLSPrivateKeyFile = path.Join(kf.CertDirectory, "kubelet.key")

		canReadCertAndKey, err := certutil.CanReadCertAndKey(kc.TLSCertFile, kc.TLSPrivateKeyFile)
		if err != nil {
			return nil, err
		}
		if !canReadCertAndKey {
			hostName, err := nodeutil.GetHostname(kf.HostnameOverride)
			if err != nil {
				return nil, err
			}
			cert, key, err := certutil.GenerateSelfSignedCertKey(hostName, nil, nil)
			if err != nil {
				return nil, fmt.Errorf("unable to generate self signed cert: %v", err)
			}

			if err := certutil.WriteCert(kc.TLSCertFile, cert); err != nil {
				return nil, err
			}

			if err := keyutil.WriteKey(kc.TLSPrivateKeyFile, key); err != nil {
				return nil, err
			}

			klog.V(4).Infof("Using self-signed cert (%s, %s)", kc.TLSCertFile, kc.TLSPrivateKeyFile)
		}
	}

	tlsCipherSuites, err := cliflag.TLSCipherSuites(kc.TLSCipherSuites)
	if err != nil {
		return nil, err
	}

	minTLSVersion, err := cliflag.TLSVersion(kc.TLSMinVersion)
	if err != nil {
		return nil, err
	}

	tlsOptions := &server.TLSOptions{
		Config: &tls.Config{
			MinVersion:   minTLSVersion,
			CipherSuites: tlsCipherSuites,
		},
		CertFile: kc.TLSCertFile,
		KeyFile:  kc.TLSPrivateKeyFile,
	}

	if len(kc.Authentication.X509.ClientCAFile) > 0 {
		clientCAs, err := certutil.NewPool(kc.Authentication.X509.ClientCAFile)
		if err != nil {
			return nil, fmt.Errorf("unable to load client CA file %s: %v", kc.Authentication.X509.ClientCAFile, err)
		}
		// Specify allowed CAs for client certificates
		tlsOptions.Config.ClientCAs = clientCAs
		// Populate PeerCertificates in requests, but don't reject connections without verified certificates
		tlsOptions.Config.ClientAuth = tls.RequestClientCert
	}

	return tlsOptions, nil
}

// SetupSignalHandler registered for SIGTERM and SIGINT. A stop channel is returned
// which is closed on one of these signals. If a second signal is caught, the program
// is terminated with exit code 1.
func SetupSignalHandler() <-chan struct{} {
	close(onlyOneSignalHandler) // panics when called twice

	shutdownHandler = make(chan os.Signal, 2)

	stop := make(chan struct{})
	signal.Notify(shutdownHandler, shutdownSignals...)
	go func() {
		<-shutdownHandler
		close(stop)
		<-shutdownHandler
		os.Exit(1) // second signal. Exit directly.
	}()

	return stop
}