code: func mountFromMain() {
  	runtime.LockOSThread()
  	flag.Parse()
  
  	var options *mountOptions
  
  	if err := json.NewDecoder(os.Stdin).Decode(&options); err != nil {
  		fatal(err)
  	}
  
  	if err := os.Chdir(flag.Arg(0)); err != nil {
  		fatal(err)
  	}
  
  	if err := unix.Mount(options.Device, options.Target, options.Type, uintptr(options.Flag), options.Label); err != nil {
  		fatal(err)
  	}
  
  	os.Exit(0)
  }
docs: // mountfromMain is the entry-point for docker-mountfrom on re-exec.