def exec(self, container_id, cmd, pid=False):
        pid, container_dir = self._dict_of_pids[container_id]
        nsentr_cmd = 'nsenter --target {pid} --pid --mnt --net --ipc --uts chroot {container_dir} '.format(pid=str(pid), container_dir=container_dir)
        subprocess.run(shlex.split(nsentr_cmd))