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YPSERV(8)				 Reference Manual				YPSERV(8)

       ypserv - NIS server

       /usr/sbin/ypserv [ -b ] [ -d [ path ] ] [ -p port ]

       The  Network Information Service (NIS) provides a simple network lookup service consisting
       of databases and processes.  The databases are gdbm files in a directory  tree  rooted  at

       The  ypserv  daemon  is	typically  activated  at system startup.  ypserv runs only on NIS
       server machines with a complete NIS database. On other machines using  the  NIS	services,
       you  have  to run ypbind as client or under Linux you could use the libc with NYS support.
       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. On startup or when
       receiving the signal SIGHUP, ypserv parses the file /etc/ypserv.conf.

       -d --debug [path]
	      Causes the server to run in debugging mode. Normally, ypserv  reports  only  errors
	      (access  violations, dbm failures) using the syslog(3) facility. In debug mode, the
	      server does not background itself and prints extra status messages  to  stderr  for
	      each  request that it revceives.	path is an optionally parameter.  ypserv is using
	      this directory instead of /var/yp

       -b --dns
	      If we don't find the host in the hosts maps, we query the DNS (Domain Name Service)
	      service  for  more  host	information. This is done in an extra subprocess.  ypserv
	      ignores the YP_INTERDOMAIN keys for dns lookup.

       -p --port port
	      ypserv will bind itself to this port.  This makes it possible to have a router fil-
	      ter  packets  to	the NIS ports, so that access to the NIS server from hosts on the
	      Internet can be restricted.

       -v --version
	      Prints the version number

       In general, any remote user can issue an RPC to ypserv and retrieve the contents  of  your
       NIS  maps, if he knows your domain name. To prevent such unauthorized transactions, ypserv
       supports a feature called securenets which can be used to restrict access to a  given  set
       of  hosts.  At startup or when arriving the SIGHUP Signal, ypserv will attempt to load the
       securenets information from a file called /var/yp/securenets .  This file contains entries
       that  consist  of  a netmask and a network pair separated by white spaces.  Lines starting
       with ``#'' are considered to be comments.

       A sample securenets file might look like this:

	      # allow connections from local host -- necessary
	      # same as
	      # allow connections from any host
	      # on the network
	      # allow connections from any host
	      # between and

       If ypserv receives a request from an address that fails to match a rule, the request  will
       be  ignored  and a warning message will be logged. If the /var/yp/securenets file does not
       exist, ypserv will allow connections from any host.

       In the /etc/ypserv.conf you could specify some access rules for special	maps  and  hosts.
       But  it	is  not  very  secure, it makes the life only a little bit harder for a potential
       hacker. If a mapname doesn't match a rule, ypserv will look for the YP_SECURE key  in  the
       map. If it exists, ypserv will only allow requests on a reserved port.

       For  security  reasons, ypserv will only accept ypproc_xfr requests for updating maps from
       the same master server as the old one. This means, you have to reinstall the slave servers
       if you change the master server for a map.

       /etc/ypserv.conf /var/yp/securenets

       domainname(1),  ypcat(1),  ypmatch(1),  ypserv.conf(5),	netgroup(5),  makedbm(8), revnet-
       group(8), ypinit(8), yppoll(8), yppush(8), ypset(8), ypwhich(8), ypxfr(8), rpc.ypxfrd(8)

       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.

       ypserv was written by Peter Eriksson <pen@lysator.liu.se>.  Thorsten Kukuk <kukuk@suse.de>
       added support for master/slave server and is the new Maintainer.

YP Server				   August 2001					YPSERV(8)
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