code: func (o *OSValidator) Validate(spec SysSpec) (error, error) {
  	os, err := exec.Command("uname").CombinedOutput()
  	if err != nil {
  		return nil, errors.Wrap(err, "failed to get os name")
  	}
  	return nil, o.validateOS(strings.TrimSpace(string(os)), spec.OS)
  }
docs: // Validate is part of the system.Validator interface.