NAME

       ypserv - NIS Server

SYNOPSIS

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

DESCRIPTION

       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 network. On startup ypserv
       parses the file /etc/ypserv.conf.

OPTIONS

       -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

       -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

SECURITY

       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 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 or network/number of bits of netmask entries. One
       per line. Lines starting with “#” are considered to be comments.

       A sample securenets file might look like this:

               # allow connections from local host -- necessary
               host 127.0.0.1
               host ::1
               # same as 255.255.255.255 127.0.0.1
               #
               # allow connections from any host
               # on the 131.234.223.0 network
               255.255.255.0   131.234.223.0
               # allow connections from any host
               # between 131.234.214.0 and 131.234.215.255
               255.255.254.0   131.234.214.0
               # allow some IPv6 connections
               FE80::0202:B3FF::/96
               # allow IPv6 connections from all machines
               ::/0

       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.

FILES

       /etc/ypserv.conf
           configuration file.

       /var/yp/securenets
           which hosts are allowed to contact ypserv.

SEE ALSO

       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.

AUTHOR

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