The NFS Exports module lists all exported directories. Clicking Add a new export will bring you to the Create Export page, shown below.
In the above figure, you can see that the module allows you to select a directory to export, and choose a number of options for that directory. To choose what host(s) can access the exported directory, you can select from several access control options. Everyone specifies that anyone may mount the directory. Host(s) allows you to specify one or more hostnames or IP's that may mount the directory. The other options provide various methods of allowing groups of systems on the network to access the directory.
The Make symbolic links relative option can be used to convert an absolute symbolic link to a relative link. When the directory is to be mounted on a mount point different from that of the exported directory, it may be necessary to enable this for symbolic links to function correctly. The next option, Clients must be on secure port? isn't really as secure as it might sound, as the NFS in use on most free Unices is not very secure. The effect of turning this option on is that NFS will insist upon a connection on ports below 1024. This does improve security in some circumstances, but may interfere with Windows clients mounting the exported directory.
In the Export Security section you can specify several other security options, including the ability to treat some UID's and/or GID's as untrusted users. This section also provides fields for declaring what user and group name will be used for the untrusted users permissions.