Working with Standard POSIX Permissions
Among other things, POSIX permissions define a permission structure for accessing files and folders. POSIX permissions are used not only in file sharing on a network but also on the Unix computer itself. Because OS X (and, therefore, Mountain Lion Server) has Unix at its core, POSIX permissions are used on all files and folders on every user’s Mac.
For any given file, folder, or volume, standard POSIX permissions have only four types of access that you can set for Owner, Group, and Others or Everyone:
Read and write: Gives full access to a shared folder or file. A user can open and save files located on the server-based folder and can copy files to the folder.
Read-only: Users can open the shared folder and files as well as copy a file or folder to their computer. But users with read-only access can’t save changes to files that they open in the shared folder, and they can’t add files to the shared folder or delete files.
Write-only: Users can only copy a file into a write-only ...