Add a default cluster dns name config

It is very handy to be able to store the default cluster dns name so
that I can fire up and teardown clusters easily without losing that
setting.

It's important to note that this default will only be applied at cluster
creation time. If you have an existing cluster config, the name default
name will not be changed if you added the config after starting the
cluster the first time.

Author: wt

cmd/minikube/cmd/config/config.go

@@ -172,6 +172,10 @@ var settings = []Setting{
 		name: config.MaxAuditEntries,
 		set:  SetInt,
 	},
+	{
+		name: config.DefaultClusterDNSDomain,
+		set:  SetString,
+	},
 }
 
 // ConfigCmd represents the config command

cmd/minikube/cmd/start.go

@@ -161,6 +161,8 @@ func runStart(cmd *cobra.Command, _ []string) {
 	}
 	defer pkgtrace.Cleanup()
 
+	viper.SetDefault(config.DefaultClusterDNSDomain, constants.DefaultClusterDNSDomain)
+
 	displayVersion(version.GetVersion())
 	go download.CleanUpOlderPreloads()
 

cmd/minikube/cmd/start_flags.go

@@ -221,7 +221,9 @@ func initKubernetesFlags() {
 		Valid components are: kubelet, kubeadm, apiserver, controller-manager, etcd, proxy, scheduler
 		Valid kubeadm parameters: `+fmt.Sprintf("%s, %s", strings.Join(bsutil.KubeadmExtraArgsAllowed[bsutil.KubeadmCmdParam], ", "), strings.Join(bsutil.KubeadmExtraArgsAllowed[bsutil.KubeadmConfigParam], ",")))
 	startCmd.Flags().String(featureGates, "", "A set of key=value pairs that describe feature gates for alpha/experimental features.")
-	startCmd.Flags().String(dnsDomain, constants.ClusterDNSDomain, "The cluster dns domain name used in the Kubernetes cluster")
+
+	startCmd.Flags().String(dnsDomain, constants.DefaultClusterDNSDomain, "The cluster dns domain name used in the Kubernetes cluster")
+
 	startCmd.Flags().Int(apiServerPort, constants.APIServerPort, "The apiserver listening port")
 	startCmd.Flags().String(apiServerName, constants.APIServerName, "The authoritative apiserver hostname for apiserver certificates and connectivity. This can be used if you want to make the apiserver available from outside the machine")
 	startCmd.Flags().StringSliceVar(&apiServerNames, "apiserver-names", nil, "A set of apiserver names which are used in the generated certificate for kubernetes.  This can be used if you want to make the apiserver available from outside the machine")
@@ -560,6 +562,11 @@ func generateNewConfigFromFlags(cmd *cobra.Command, k8sVersion string, rtime str
 		out.WarningT("--network flag is only valid with the docker/podman, qemu, kvm, and vfkit drivers, it will be ignored")
 	}
 
+	defaultClusterDNSDomain := viper.GetString(dnsDomain)
+	if defaultClusterDNSDomain == constants.DefaultClusterDNSDomain {
+		defaultClusterDNSDomain = viper.GetString(config.DefaultClusterDNSDomain)
+	}
+
 	validateHANodeCount(cmd)
 
 	checkNumaCount(k8sVersion)
@@ -636,7 +643,7 @@ func generateNewConfigFromFlags(cmd *cobra.Command, k8sVersion string, rtime str
 			APIServerName:          viper.GetString(apiServerName),
 			APIServerNames:         apiServerNames,
 			APIServerIPs:           apiServerIPs,
-			DNSDomain:              viper.GetString(dnsDomain),
+			DNSDomain:              defaultClusterDNSDomain,
 			FeatureGates:           viper.GetString(featureGates),
 			ContainerRuntime:       rtime,
 			CRISocket:              viper.GetString(criSocket),

pkg/minikube/config/config.go

@@ -58,6 +58,9 @@ const (
 	EmbedCerts = "EmbedCerts"
 	// MaxAuditEntries is the maximum number of audit entries to retain
 	MaxAuditEntries = "MaxAuditEntries"
+	// DefaultDnsDomain is the key for the default dns domain name when creating
+	// a cluster
+	DefaultClusterDNSDomain = "DefaultClusterDNSDomain"
 )
 
 var (

pkg/minikube/constants/constants.go

@@ -75,7 +75,7 @@ const (
 	// APIServerName is the default API server name
 	APIServerName = "minikubeCA"
 	// ClusterDNSDomain is the default DNS domain
-	ClusterDNSDomain = "cluster.local"
+	DefaultClusterDNSDomain = "cluster.local"
 	// DefaultServiceCIDR is The CIDR to be used for service cluster IPs
 	DefaultServiceCIDR = "10.96.0.0/12"
 	// HostAlias is a DNS alias to the container/VM host IP