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ypfiles(4)							   ypfiles(4)

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


  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 con-
  sists	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

  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 subdirectory 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 system.  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 informa-
  tion 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 mas-
  ter 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 addi-
  tion,	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 mas-
  ter 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.




  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).