YP(8)                     BSD System Manager's Manual                    YP(8)

NAME
     yp -- description of the YP/NIS system

SYNOPSIS
     yp

DESCRIPTION
     The YP subsystem allows network access to directory information hosted by
     NIS servers.  OS X support is provided through the functions getpwent(3),
     getgrent(3), getfsent(3), getnetgrent(3), gethostent(3), getnetent(3),
     getrpcent(3), getprotoent(3), getservent(3), ethers(3) and other related
     functions.  Queries to NIS servers are sent by the opendirectoryd daemon.
     The configuration of NIS clients is further described in the
     opendirectoryd(8) manual page.

     The YP subsystem is started automatically by launchd(8) if an NIS domain
     is specified in the /etc/defaultdomain configuration file, and if the
     directory /var/yp exists (which it does in the default distribution).

     NIS is an RPC-based client/server system that allows a group of machines
     within an NIS domain to share a common set of configuration files.  This
     permits a system administrator to set up NIS client systems with only
     minimal configuration data and add, remove or modify configuration data
     from a single location.

     The canonical copies of all NIS information are stored on a single
     machine called the NIS master server.  The databases used to store the
     information are called NIS maps.  A single NIS server can support several
     domains at once, therefore it is possible to have several such directo-
     ries, one for each supported domain.  Each domain will have its own inde-
     pendent set of maps.

     Client NIS systems receive all NIS data in ASCII form.

     There are three main types of NIS systems:

     1.   NIS clients, which query NIS servers for information.

     2.   NIS master servers, which maintain the canonical copies of all NIS
          maps.

     3.   NIS slave servers, which maintain backup copies of NIS maps that are
          periodically updated by the master.

     OS X systems may be configured as NIS clients, but not as master or slave
     servers.

     A NIS client establishes what is called a binding to a particular NIS
     server using the ypbind(8) daemon.  The ypbind(8) utility checks the sys-
     tem's default domain (as set by the domainname(1) command) and begins
     broadcasting RPC requests on the local network.  These requests specify
     the name of the domain for which ypbind(8) is attempting to establish a
     binding.  If a server that has been configured to serve the requested
     domain receives one of the broadcasts, it will respond to ypbind(8),
     which will record the server's address.  If there are several servers
     available (a master and several slaves, for example), ypbind(8) will use
     the address of the first one to respond.  From that point on, the client
     system will direct all of its NIS requests to that server.  The ypbind(8)
     utility will occasionally ``ping'' the server to make sure it is still up
     and running.  If it fails to receive a reply to one of its pings within a
     reasonable amount of time, ypbind(8) will mark the domain as unbound and
     begin broadcasting again in the hopes of locating another server.

     NIS master and slave servers handle all NIS requests with the ypserv(8)
     daemon.  The ypserv(8) utility is responsible for receiving incoming
     requests from NIS clients, translating the requested domain and map name
     to a path to the corresponding database file and transmitting data from
     the database back to the client.  There is a specific set of requests
     that ypserv(8) is designed to handle, most of which are implemented as
     functions within the standard system libraries:

     yp_order()   check the creation date of a particular map

     yp_master()  obtain the name of the NIS master server for a given
                  map/domain

     yp_match()   lookup the data corresponding to a given in key in a partic-
                  ular map/domain

     yp_first()   obtain the first key/data pair in a particular map/domain

     yp_next()    pass ypserv(8) a key in a particular map/domain and have it
                  return the key/data pair immediately following it (the func-
                  tions yp_first() and yp_next() can be used to do a sequen-
                  tial search of an NIS map)

     yp_all()     retrieve the entire contents of a map

     There are a few other requests which ypserv(8) is capable of handling
     (i.e., acknowledge whether or not you can handle a particular domain
     (YPPROC_DOMAIN), or acknowledge only if you can handle the domain and be
     silent otherwise (YPPROC_DOMAIN_NONACK)) but these requests are usually
     generated only by ypbind(8) and are not meant to be used by standard
     utilities.

HISTORY
     The YP subsystem was written from the ground up by Theo de Raadt to be
     compatible to Sun's implementation.  Bug fixes, improvements and NIS
     server support were later added by Bill Paul.  The server-side code was
     originally written by Peter Eriksson and Tobias Reber and is subject to
     the GNU Public License.  No Sun code was referenced.

     OS X NIS client software is derived from FreeBSD.

BSD                              April 5, 1993                             BSD