When using chmod -R o+rx /data , you set the execute permission on all directories as well as files in the /data directory.
To set the execute permission to directories only, and not to files, use chmod -R o+rX /data . The uppercase X ensures that files will not get the execute permission unless the file has already set the execute permission for some of the entities. That makes X the more intelligent way of dealing with execute permissions; it will avoid setting that permission on files where it is not needed.
原文：http://www.cnblogs.com/rusking/p/5613243.html