YPSERV(8)                      Reference Manual                      YPSERV(8)

       ypserv - NIS server

       /usr/sbin/ypserv [ -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 /var/yp.

       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  net-
       work. 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  back-
              ground  itself  and  prints  extra status messages to stderr for
              each request that it revceives.  path is an  optionally  parame-
              ter.  ypserv is using this directory instead of /var/yp

       -p --port port
              ypserv will bind itself to this port.  This makes it possible to
              have a router filter 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 net-
       mask 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 con-
       nections 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), revnetgroup(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 <>.  Thorsten
       Kukuk <> added support for master/slave server and is  the
       new Maintainer.

YP Server                         August 2001                        YPSERV(8)