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YPSERV(8)                   System Manager's Manual                  YPSERV(8)

       ypserv, ypbind, ypxfrd - NIS server and binder processes

       /usr/etc/ypserv [ -d ]

       /usr/etc/ypbind [-s] [-ypset|-ypsetme]

       ypxfrd [ -x ]

       This  program  is  available  with the Networking software installation
       option.  Refer to for information on how to install optional software.

       The Network Information Service (NIS) provides a simple network  lookup
       service  consisting  of  databases  and  processes.   The databases are
       dbm(3X) files in a directory tree rooted at /var/yp.  These  files  are
       described  in  ypfiles(5).   The processes are /usr/etc/ypserv, the NIS
       database lookup server, and /usr/etc/ypbind, the NIS binder.  The  pro-
       grammatic  interface  to  the  NIS  service is described in ypclnt(3N).
       Administrative tools are described in yppush(8),  ypxfr(8),  yppoll(8),
       ypwhich(8),  and  ypset(8).   Tools to see the contents of NIS maps are
       described in ypcat(1), and ypmatch(1).  Database generation and mainte-
       nance tools are described in ypinit(8), ypmake(8), and makedbm(8).

       Both ypserv and ypbind are daemon processes typically activated at sys-
       tem startup time from /etc/rc.local.  ypserv runs only  on  NIS  server
       machines  with  a  complete  NIS database.  ypbind runs on all machines
       using the NIS services, both NIS servers and clients.

       ypxfrd transfers entire NIS maps in an efficient manner.   For  systems
       that  use  this  daemon,  map transfers will be 10 to 100 times faster,
       depending on the map.  To use this daemon, ypxfrd should be  run  on  a
       server  running  SunOS  release  4.1.  ypxfr will attempt to use ypxfrd
       first, if that fails, it will print a warning and then  use  the  older
       transfer method.

       The  ypserv  daemon's primary function is to look up information in its
       local database of NIS maps.  The operations  performed  by  ypserv  are
       defined  for  the implementor by the YP Protocol Specification, and for
       the programmer by the header file rpcsvc/yp_prot.h.   Communication  to
       and  from  ypserv  is  by  means  of  RPC  calls.  Lookup functions are
       described in ypclnt(3N), and are supplied as  C-callable  functions  in
       the  C library.  There are four lookup functions, all of which are per-
       formed on a specified map within some  NIS  domain:  match,  get_first,
       get_next,  and  get_all.   The match operation takes a key, and returns
       the associated value.  The get_first operation returns the  first  key-
       value  pair  from  the  map,  and get_next can be used to enumerate the
       remainder.  get_all ships the  entire  map  to  the  requester  as  the
       response to a single RPC request.

       Two  other  functions supply information about the map, rather than map
       entries: get_order_number, and get_master_name.  In  fact,  both  order
       number  and  master  name  exist in the map as key-value pairs, but the
       server will not return either through the normal lookup functions.   If
       you  examine  the  map  with makedbm(8), however, they will be visible.
       Other functions are used within the NIS service subsystem  itself,  and
       are   not   of   general   interest   to  NIS  clients.   They  include
       do_you_serve_this_domain?,   transfer_map,   and    reinitialize_inter-

       The function of ypbind is to remember information that lets client pro-
       cesses on a single node communicate with some ypserv  process.   ypbind
       must run on every machine which has NIS client processes; ypserv may or
       may not be running on the same node, but must be running  somewhere  on
       the network.

       The information ypbind remembers is called a binding -- the association
       of a domain name with the internet address of the NIS server,  and  the
       port  on that host at which the ypserv process is listening for service
       requests. This information is cached in the  directory  /var/yp/binding
       using a filename of domainname.version.

       The  process of binding is driven by client requests.  As a request for
       an unbound domain comes in, the ypbind process broadcasts  on  the  net
       trying  to  find  a ypserv process that serves maps within that domain.
       Since the binding is established by  broadcasting,  there  must  be  at
       least  one ypserv process on every net.  If the client is running in C2
       secure mode, then ypbind will only accept bindings to servers where the
       ypserv process is running as root.  Once a domain is bound by a partic-
       ular ypbind, that same binding is given to every client process on  the
       node.   The  ypbind  process  on the local node or a remote node may be
       queried for the binding of a particular domain by using the  ypwhich(1)

       Bindings and rebindings are handled transparently by the C library rou-
       tines. If ypbind is unable to speak to the ypserv  process  it's  bound
       to,  it  marks the domain as unbound, tells the client process that the
       domain is unbound, and tries to bind the domain once  again.   Requests
       received  for an unbound domain will wait until the domain requested is
       bound.  In general, a bound domain is marked as unbound when  the  node
       running ypserv crashes or gets overloaded.  In such a case, ypbind will
       to bind any NIS server (typically  one  that  is  less-heavily  loaded)
       available on the net.

       ypbind  also  accepts  requests  to  set  its  binding for a particular
       domain.  The request is usually generated by the NIS subsystem  itself.
       ypset(8)  is  a  command  to access the set_domain facility.  It is for
       unsnarling messes. Note: the set_domain procedure only accepts requests
       from processes running as root.

       -d     The  NIS  service should go to the DNS (Domain Name Service) for
              more host information.

       -s     Secure.  When specified, only ypservers bound to a reserved port
              are used.  This allows for a slight increase in security in com-
              pletely controlled environments, where there  are  no  computers
              operated  by  untrusted individuals.  It offers no real increase
              in security.

       -v     Do not fork when ypxfrd is called multiple times.

       -ypset ypset(8) may be used to change the binding.  This option is very
              dangerous,  and  only  should  be used for debugging the network
              from a remote machine.

              ypset(8) may be issued from this machine, security is  based  on
              IP  address  checking,  which  can  be defeated on network where
              untrusted individuals may inject packets.  This  option  is  not

       If the file /var/yp/ypserv.log exists when ypserv starts up, log infor-
       mation will be written to this file when error conditions arise.

       The file(s) /var/yp/binding/domainname.version will be created to speed
       up  the binding process.  These files cache the last successful binding
       created for the given domain, when a binding is requested  these  files
       are checked for validity and then used.

       domainname(1),  ypcat(1),  ypmatch(1),  dbm(3X), ypclnt(3N), ypfiles(5)
       makedbm(8),  ypmake(8),  ypinit(8),  yppoll(8),  yppush(8),   ypset(8),
       ypwhich(8), ypxfr(8),

       Both  ypbind  and  ypserv support multiple domains.  The ypserv process
       determines the domains it serves by looking for directories of the same
       name  in  the  directory  /var/yp.   It  will  reply  to all broadcasts
       requesting yp  service  for  that  domain.   Additionally,  the  ypbind
       process can maintain bindings to several domains and their servers, the
       default domain is however the one specified by the  domainname(1)  com-
       mand at startup time.

       The  Network Information Service (NIS) was formerly known as Sun Yellow
       Pages (YP).  The functionality of the two remains the  same;  only  the
       name  has  changed.  The name Yellow Pages is a registered trademark in
       the United Kingdom of British Telecommunications plc, and  may  not  be
       used without permission.

                               17 December 1987                      YPSERV(8)