Open System Services NFS Overview

Mount Protocol
The mount protocol is separate from, but related to, the NFS protocol. It provides
operating-system-specific services to get the Network File System started: looking up server
pathnames, validating user identity, and checking access permissions. Clients use the mount protocol
to get the first file handle, which allows them access to a remote fileset.
The mount protocol is kept separate from the NFS protocol to make it easy to plug in new
access-checking and validation methods without changing the NFS server protocol.
Note that the mount protocol definition implies that servers must maintain state information, because
the server maintains a list of mount requests from clients. The mount list information is not critical
for the correct functioning of either the client or the server. It is intended for advisory use only; for
example, to warn possible clients when a server is going down.
PCNFSD Protocol
The PCNFSD protocol, like the mount protocol, is separate from, but related to, the NFS protocol.
It provides user ID authentication and print-spooling services.
PCNFSD is a protocol defined by Sun Microsystems, Inc. to allow PC-type clients access to NFS
servers. PCNFSD is required because most PCs do not maintain their own authentication protocols.
The PCNFSD protocol allows clients that do not support UNIX authentication to specify authentication
information to NFS in the correct format.
PCNFSD also provides print spooling capabilities. Using PCNFSD, clients mount specially designated
spool directories (for example, /var/spool/pcnfs) into which print output is placed, using
standard NFS write mechanisms. Clients then use PCNFSD commands to insert those files as print
jobs into appropriate spooler locations.
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