Networking Guide
Chapter 7, Configuring the Network Information Service (NIS)

NIS maps

NIS maps

The configuration information managed with NIS is typically stored in ASCII files when NIS is not in use. NIS master servers convert the information into NIS maps for storage and transfer by NIS programs.

Each NIS map is an ndbm database. An ndbm database consists of a pair of files that are created by calls to the ndbm(NS) library package. One file contains a directory (that is, a bitmap of indices accessed by a hash table); the other file contains data. Because of the non-ASCII file structure imposed by ndbm, you must use NIS tools (such as ypxfr and yppush) to transfer maps from one machine to another.

The use of maps to manage data permits NIS to add a timestamp and the identity of the source (that is, the name of the host serving as the master). A host uses the timestamp to determine if the contents of the map it is receiving are newer than data it already has. The identity of the master allows a nonmaster server to request an immediate update.

NIS maps are created when an NIS master server is initialized or as needed using NIS commands. When an NIS master server is being initialized, the initialization process creates the maps listed in the file /etc/yp/YP_MAP_X_LATE. These maps are propagated to nonmaster servers when these servers enter multiuser mode for the first time after being initialized as NIS servers. Additional maps can be created on the master server at any time using the procedures described in ``Creating NIS maps''.