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