ypfiles(4)						     Kernel Interfaces Manual							ypfiles(4)

NAME

       ypfiles - Network Information Service (NIS) database and directory structure

DESCRIPTION

       The  NIS database lookup service uses a database of dbm/ndbm, btree, or hash files in the /var/yp directory hierarchy.  A dbm/ndbm database
       consists of two files created by calls to the dbminit(3) function.  One has the filename extension .pag and  the  other	has  the  filename
       extension  .dir.  For instance, the database named hosts.byname, is implemented by the pair of files hosts.byname.pag and hosts.byname.dir.
       A btree or hash database consists of a single file created by calls to the dbopen(3) function.  A btree file  has  the  filename  extension
       .btree; a hash file has the extension .hash.

       A dbm/ndbm database served by NIS is called an NIS map.	A NIS domain is a named set of NIS maps.  Each NIS domain is implemented as a sub-
       directory of /var/yp containing the maps.  The number of NIS domains that can exist is unlimited.  Each domain can contain  any	number	of
       maps.

       The  NIS maps are not required by the NIS lookup service, although they may be required for the normal operation of other parts of the sys-
       tem.  The NIS lookup service serves all maps. If the map exists in a given domain and a client asks about it, NIS will serve it.  There is,
       however, a set of default maps that the NIS service serves.  The files representing these maps are listed in this description under Files.

       For  a  map to be accessible consistently, it must exist on all NIS servers that serve the domain.  To provide data consistency between the
       replicated maps, an entry to execute the ypxfr command periodically should be made in the /var/spool/cron/crontab/root file on  each  slave
       server.	 More information on this topic is in ypxfr(8).  An entry in the /var/spool/cron/crontab/root file must not exist, either on a NIS
       master server or on a pure NIS client machine.

       The NIS maps should contain two distinguished key-value pairs.  The first is the key YP_LAST_MODIFIED, whose value is a 10-character  ASCII
       order number.  The order number should be the UNIX time in seconds when the map was built.  The second key is YP_MASTER_NAME, with the name
       of the NIS master server as a value.  The makedbm(8) command generates both key-value pairs automatically.  A map  that	does  not  contain
       both  key-value	pairs can be served by the NIS, but the ypserv process will not be able to return values for ``Get order number'' or ``Get
       master name'' requests.	In addition, the values of these two keys are used by ypxfr(8) when it transfers a map from a master NIS server to
       a slave.

       Before  they  can be properly accessed, the NIS maps must be initially set up for both masters and slaves by using the ypsetup(8) function.
       Further, NIS maps must be generated and modified only at the master server location.  Copies of the master server  NIS  maps  can  then	be
       transferred  to	the  slave  servers  using the ypxfr(8) function.  If ypxfr is unable to determine a map's location, or if it is unable to
       determine whether the local copy is more recent than the master copy, extra command line switches must be set when it is executed.

       After the server databases are set up, the contents of some maps may change.  In general, some ASCII source version of the database  exists
       on  the master.	This version should be changed with a standard text editor.  The update is incorporated into the NIS map and is propagated
       from the master to the slaves by running /var/yp/Makefile. All maps must have entries in /var/yp/Makefile. If an  NIS  map  is  added,  the
       /var/yp/Makefile  must be edited to support the new map.  The makefile uses makedbm(8) to generate the NIS map on the master, and yppush(8)
       to propagate the changed map to the slaves.  The yppush(8) command is a client of the map ypservers, which lists all of the NIS servers.

FILES

       /var/yp/src/passwd
       /var/yp/src/group
       /var/yp/src/hosts
       /var/yp/src/networks
       /var/yp/src/services
       /var/yp/src/protocols
       /var/yp/src/netgroup

RELATED INFORMATION

       Commands: makedbm(8), rpcinfo(8), ypmake(8), yppoll(8), yppush(8), ypserv(8), ypsetup(8), ypxfr(8).

       Functions: btree(3), dbm(3), hash(3), ndbm(3).  delim off

																	ypfiles(4)