Provide warning message for unnecessary sudo

If minikube is started with root privilege and vm-driver is
not hyperV or none, then a warning message is displayed.

cmd/minikube/cmd/start.go

@@ -23,6 +23,7 @@ import (
 	"net"
 	"os"
 	"os/exec"
+	"os/user"
 	"path/filepath"
 	"runtime"
 	"strconv"
@@ -172,6 +173,15 @@ func runStart(cmd *cobra.Command, args []string) {
 	console.OutStyle(console.Happy, "minikube %s on %s (%s)", version.GetVersion(), runtime.GOOS, runtime.GOARCH)
 	validateConfig()
 
+	currentUser, err := user.Current()
+
+	// Display warning if minikube is being started with root and vmDriver is not HyperV
+	if err != nil {
+		glog.Errorf("Error getting the current user: %v", err)
+	} else if currentUser.Name == "root" && !(viper.GetString(vmDriver) == "hyperv" || viper.GetString(vmDriver) == "none") {
+		console.OutStyle(console.WarningType, "Please don't run minikube as root or with 'sudo' privileges. It isn't necessary.")
+	}
+
 	oldConfig, err := cfg.Load()
 	if err != nil && !os.IsNotExist(err) {
 		exit.WithCode(exit.Data, "Unable to load config: %v", err)