def _generate_contents(self, tar):
        """
        Adds configuration files to tarfile instance.

        :param tar: tarfile instance
        :returns: None
        """
        uci = self.render(files=False)
        # create a list with all the packages (and remove empty entries)
        packages = packages_pattern.split(uci)
        if '' in packages:
            packages.remove('')
        # create an UCI file for each configuration package used
        for package in packages:
            lines = package.split('\n')
            package_name = lines[0]
            text_contents = '\n'.join(lines[2:])
            self._add_file(tar=tar,
                           name='{0}{1}'.format(config_path, package_name),
                           contents=text_contents)
Adds configuration files to tarfile instance.

        :param tar: tarfile instance
        :returns: None