libmachine/mcnutils/b2d.go
func MakeDiskImage(publicSSHKeyPath string) (*bytes.Buffer, error) {
	magicString := "boot2docker, please format-me"

	buf := new(bytes.Buffer)
	tw := tar.NewWriter(buf)

	// magicString first so the automount script knows to format the disk
	file := &tar.Header{Name: magicString, Size: int64(len(magicString))}

	log.Debug("Writing magic tar header")

	if err := tw.WriteHeader(file); err != nil {
		return nil, err
	}

	if _, err := tw.Write([]byte(magicString)); err != nil {
		return nil, err
	}

	// .ssh/key.pub => authorized_keys
	file = &tar.Header{Name: ".ssh", Typeflag: tar.TypeDir, Mode: 0700}
	if err := tw.WriteHeader(file); err != nil {
		return nil, err
	}

	log.Debug("Writing SSH key tar header")

	pubKey, err := ioutil.ReadFile(publicSSHKeyPath)
	if err != nil {
		return nil, err
	}

	file = &tar.Header{Name: ".ssh/authorized_keys", Size: int64(len(pubKey)), Mode: 0644}
	if err := tw.WriteHeader(file); err != nil {
		return nil, err
	}

	if _, err := tw.Write([]byte(pubKey)); err != nil {
		return nil, err
	}

	file = &tar.Header{Name: ".ssh/authorized_keys2", Size: int64(len(pubKey)), Mode: 0644}
	if err := tw.WriteHeader(file); err != nil {
		return nil, err
	}

	if _, err := tw.Write([]byte(pubKey)); err != nil {
		return nil, err
	}

	if err := tw.Close(); err != nil {
		return nil, err
	}

	return buf, nil
}
func MakeDiskImage(publicSSHKeyPath string) (*bytes.Buffer, error) {
	magicString := "boot2docker, please format-me"

	buf := new(bytes.Buffer)
	tw := tar.NewWriter(buf)

	// magicString first so the automount script knows to format the disk
	file := &tar.Header{Name: magicString, Size: int64(len(magicString))}

	log.Debug("Writing magic tar header")

	if err := tw.WriteHeader(file); err != nil {
		return nil, err
	}

	if _, err := tw.Write([]byte(magicString)); err != nil {
		return nil, err
	}

	// .ssh/key.pub => authorized_keys
	file = &tar.Header{Name: ".ssh", Typeflag: tar.TypeDir, Mode: 0700}
	if err := tw.WriteHeader(file); err != nil {
		return nil, err
	}

	log.Debug("Writing SSH key tar header")

	pubKey, err := ioutil.ReadFile(publicSSHKeyPath)
	if err != nil {
		return nil, err
	}

	file = &tar.Header{Name: ".ssh/authorized_keys", Size: int64(len(pubKey)), Mode: 0644}
	if err := tw.WriteHeader(file); err != nil {
		return nil, err
	}

	if _, err := tw.Write([]byte(pubKey)); err != nil {
		return nil, err
	}

	file = &tar.Header{Name: ".ssh/authorized_keys2", Size: int64(len(pubKey)), Mode: 0644}
	if err := tw.WriteHeader(file); err != nil {
		return nil, err
	}

	if _, err := tw.Write([]byte(pubKey)); err != nil {
		return nil, err
	}

	if err := tw.Close(); err != nil {
		return nil, err
	}

	return buf, nil
}
// MakeDiskImage makes a boot2docker VM disk image.
// See https://github.com/boot2docker/boot2docker/blob/master/rootfs/rootfs/etc/rc.d/automount