Add VirtualBox headless mode.

builder/virtualbox/builder.go

@@ -30,6 +30,7 @@ type config struct {
 	DiskSize           uint          `mapstructure:"disk_size"`
 	GuestAdditionsPath string        `mapstructure:"guest_additions_path"`
 	GuestOSType        string        `mapstructure:"guest_os_type"`
+	Headless           bool          `mapstructure:"headless"`
 	HTTPDir            string        `mapstructure:"http_directory"`
 	HTTPPortMin        uint          `mapstructure:"http_port_min"`
 	HTTPPortMax        uint          `mapstructure:"http_port_max"`

builder/virtualbox/step_run.go

@@ -23,7 +23,11 @@ func (s *stepRun) Run(state map[string]interface{}) multistep.StepAction {
 	vmName := state["vmName"].(string)
 
 	ui.Say("Starting the virtual machine...")
-	command := []string{"startvm", vmName, "--type", "gui"}
+	guiArgument := "gui"
+	if config.Headless == true {
+		guiArgument = "headless"
+	}
+	command := []string{"startvm", vmName, "--type", guiArgument}
 	if err := driver.VBoxManage(command...); err != nil {
 		err := fmt.Errorf("Error starting VM: %s", err)
 		state["error"] = err