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facilitate access to Unix password database authorization, as well as printers connected to Unix systems. Note that while support for this protocol is common among PC/NFS implementations, finding a PCNFSD server is not always easy. Ironically, even as of Solaris 8, Solaris doesn't include one. You should expect that the vendor of your selected PC/NFS client can provide a PCNFSD server for the Unix server platform you have deployed. If you have trouble, you might poke around the PC/NFS vendors websites. For example, Hummingbird's ftp.hcl.com FTP server has source and binaries for its HCLNFSD protocol. Note that the HCLNFSD protocol is similar in functionality to the PCNFSD protocol, but has been enhanced to work better with the Hummingbird PC/NFS product. HCLNFSD is not compatible with the PCNFSD protocol. While several non-Hummingbird PC/NFS implementations support HCLNFSD in addition to Hummingbird, if you have a PC/NFS client that supports only the PCNFSD protocol, Hummingbird's HCLNFSD implementation will be of no use. If you are in this predicament, try using a search engine to find PCNFSD source code or binaries. For example, typing this query into www.google.com:

source code for pcnfsd

turned up this URL:

http://www.sunfreeware.com/programlist.html

which had both source and binaries (Solaris 2.6, SPARC) for PCNFSD. Obviously, URLs come and go, so don't be surprised if you find PCNFSD somewhere else.

Advanced and interesting features of some PC/NFS implementations include:

Kerberos V5 security for NFS mounts. This allows clients to access NFS servers that share filesystems via Kerberos V5 security only.

RPC/DH security for NFS mounts. This allows clients to access NFS servers that share filesystems via RPC/DH security only.

Integration with NIS+.

You should expect that future PC/NFS implementations will add features like NFS Version 4 and integration with LDAP (so that the Unix authentication database in LDAP can be accessed).

Limitations of PC/NFS

The NFS protocol is the lingua franca of file-sharing protocols in that it is implemented on the widest variety of operating system environments, both client and server. These environments include Unix (nearly all of them), Windows, NT, MacOS, MVS, OS/400, OS/2, VMS, many real-time operating systems, and systems designed for network-attached storage, such as the ONTAP system for Network Appliance's hardware. One reason why NFS has been so successful is that it is very simple. This simplicity has a price; NFS does not take the approach of supporting every arcane, operating-specific file semantic for all the environments it supports. Using NFS on non-Unix platforms, especially as a client, can limit you. This is very noticeable with PC/NFS. For example, the Windows and NT worlds have notions of enforced locking, which NFS, even via the NFS Lock Manager, does not provide. While PC/NFS implementations do their best to emulate this semantic and others, you will find that some applications work in unexpected ways over NFS.

These limitations apply to NFS Versions 2 and 3. NFS Version 4 goes a long way toward supporting Windows and NT file semantics. At the time of this writing, there were no known generally available NFS Version 4 implementations.

NFS versus SMB (CIFS)

SMB stands for Server Message Block and is the file access protocol that is native to Windows and NT. In 1996, Microsoft, the owner of the SMB protocol, renamed SMB to CIFS: the Common Internet File System. However, at the time of this writing, CIFS was not as common as NFS when it came to came to the variety of client implementations. CIFS is, however, growing in the number of server implementations. When you consider the plethora of low-end, network-attached storage boxes aimed at consumers and small office environments, that often support CIFS but not NFS, it is arguable that CIFS has surpassed NFS in the number of unique server implementations. The installed base of Windows and NT desktop computers as compared to non-Windows, non-NT desktops is a big reason for this trend.

Unix is becoming