YPSERV(8) NIS Reference Manual YPSERV(8)NAMEypserv - 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. 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
# 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
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.
BUGS
Sending the signal SIGHUP to the server can lead to a deadlock or
crash.
FILES
/etc/ypserv.conf
configuration file.
/var/yp/securenets
which hosts are allowed to contact ypserv.
SEE ALSOdomainname(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.
AUTHORypserv 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.
NIS Reference Manual 01/27/2010 YPSERV(8)
