The objects that can be shared with the NFS service include any whole or partial directory tree or a file hierarchy, including a single file. A system cannot share a file hierarchy that overlaps a file hierarchy that is already shared. Peripheral devices such as modems and printers cannot be shared.
In most UNIX system environments, a file hierarchy that can be shared corresponds to a file system or to a portion of a file system. However, because NFS works across operating systems and the concept of a file system might be meaningless in non-UNIX environments, the term file system refers to a file or file hierarchy that can be shared and mounted with NFS.