linux 中 shell脚本中执行命令：mount -t cifs 就报错is write-protected, mounting read-only 命令行不报？

linux 中 shell脚本中执行命令：mount -t cifs  就报错is write-protected, mounting read-only 命令输入相同命令就不报错怎么回事？

报错：mount: //172.17.21.30/test is write-protected, mounting read-only
mount: cannot mount //172.17.21.30/test read-only

命令：mount -t cifs //172.17.21.30/test /tmp//172.17.21.30/test -o username=topsec -o password=topsec