if I mv from one location on harddrive to another.
I don't see anything in manpage.

thanks

mv tries to preserve permissions

In my experience it always has. Thats not to say something else wont update those permissions later.

Another good tool to consider for this purpose is: rsync.

This tool specifically does support handling of permissions, modification dates and so on. Plus, "efficient synchronization." It might be more suitable to your needs.

mv destroys the file on the original space and recreates the same in another.

Basically, it cannot be done by a subordinate user unless the original file permission is set to allow "group" or "others" to execute the command. Try doing it against some 'root'-owned-files while logged as another user, learn from that. This could happen with other files (by non-root users) with exclusive permissions.

One thing, 'mv' stamps permissions on the the newly recreated file based on the 'umask' set by the system for the user executing the same.

Hope this helps.

If the source and destination are on the same block device, the "mv" command will simply rename the source. For this reason mv will seem to work very quickly. I also agree that rsync is a great tool. I think the -a flag preserves permissions and ownership and -r will strip them.