---
name: "ypserv"
section: "8"
platform: "linux"
package: "ypserv"
version: "4.2-2+b2"
release: "Debian 13 (Trixie)"
platforms: ["linux", "freebsd", "openbsd"]
url: "https://new.carta.tech/ypserv"
---

# ypserv(8)

NIS Server

## 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)](/syslog/3.md) 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)](/domainname/1.md), [**ypcat**(1)](/ypcat/1.md), [**ypmatch**(1)](/ypmatch/1.md), [**ypserv.conf**(5)](/ypserv.conf/5.md), [**netgroup**(5)](/netgroup/5.md), [**makedbm**(8)](/makedbm/8.md), [**revnetgroup**(8)](/revnetgroup/8.md), [**ypinit**(8)](/ypinit/8.md), [**yppoll**(8)](/yppoll/8.md), [**yppush**(8)](/yppush/8.md), [**ypset**(8)](/ypset/8.md), **ypwhich**(8), [**ypxfr**(8)](/ypxfr/8.md), [**rpc.ypxfrd**(8)](/rpc.ypxfrd/8.md)

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.