code: func (b *b2dISO) version() (string, error) {
  	if b == nil {
  		return "", nil
  	}
  
  	iso, err := os.Open(b.commonIsoPath)
  	if err != nil {
  		return "", err
  	}
  	defer iso.Close()
  
  	isoMetadata := make([]byte, b.volumeIDLength)
  	_, err = iso.ReadAt(isoMetadata, b.volumeIDOffset)
  	if err != nil {
  		return "", err
  	}
  
  	trimmedVersion := strings.TrimSpace(string(isoMetadata))
  
  	versionIndex := strings.Index(trimmedVersion, versionPrefix)
  	if versionIndex == -1 {
  		return "", fmt.Errorf("Did not find prefix %q in version string", versionPrefix)
  	}
  
  	// Original magic file string looks similar to this: "Boot2Docker-v0.1.0              "
  	// This will return "v0.1.0" given the above string
  	vers := trimmedVersion[versionIndex+1:]
  
  	log.Debug("local Boot2Docker ISO version: ", vers)
  	return vers, nil
  }
docs: // version scans the volume ID in b and returns its version tag.