File and print services make the network more convenient for users. Not long ago, disk drives and high-quality printers were relatively expensive, and diskless workstations were common. Today, every system has a large hard drive and many have their own high-quality laser printers, but the demand for resource-sharing services is higher than ever.
File sharing is not the same as file transfer; it is not simply the ability to move a file from one system to another. A true file-sharing system does not require you to move files across the network. It allows files to be accessed at the record level so that it is possible for a client to read a record from a file located on a remote server, update that record, and write it back to the serverwithout moving the entire file from the server to the client.
File sharing is transparent to the user and to the application software running on the user's system. Through file sharing, users and programs access files located on remote systems as if they were local files. In a perfect file-sharing environment, the user neither knows nor cares where files are actually stored.
File sharing didn't exist in the original TCP/IP protocol suite. It was added to support diskless workstations. Several TCP/IP protocols for file sharing have been defined, but two hold the lion's share of the file sharing market:
NetBIOS was originally defined by IBM. It is the basic networking used on Microsoft Windows systems. Unix systems can act as file and print servers for Windows clients by running the Samba software package that implements NetBIOS and Server Message Block (SMB) protocols.
NFS was defined by Sun Microsystems to support their diskless workstations. NFS is designed primarily for LAN applications and is implemented for all Unix systems and many other operating systems.
For file sharing between Unix systems, you will probably use NFS, as it is the most widely used Unix file-sharing protocol. If you need to support Windows clients using Unix servers, you will probably use Samba. For a detailed discussion of both of these tools, see Chapter 9.
A print server allows printers to be shared by everyone on the network. Printer sharing is not as important as file sharing, but it is a useful network service. The advantages of printer sharing are:
Fewer printers are needed, and less money is spent on printers and supplies.
Reduced maintenance. There are fewer machines to maintain, and fewer people spending time fiddling with printers.
Access to special printers. Very high-quality color printers and very high-speed printers are expensive and needed only occasionally. Sharing these printers makes the best use of expensive resources.
There are two techniques commonly used for sharing printers on a corporate network. One technique is to use the sharing services provided by Samba. This is the technique preferred by Windows clients. The other approach is to use the traditional Unix lpr command and an lpd server. Print server configuration is also covered in Chapter 9.
This chapter concludes with a discussion of the various types of TCP/IP configuration servers. Unlike email, file sharing, and print servers, configuration servers are not used on every network. However, the demand for easier installation and improved mobility makes configuration servers an important part of many networks.