nis_intro - Network Information Service (NIS) introductory
information
The Network Information Service (NIS) is a distributed
name service that allows participating hosts to share
access to a common set of system and network files. NIS
allows the system administrator to manage these shared
files on a single system.
NIS is intended for use in a secure environment only,
where gateways do not allow outside Internet access to the
NIS protocol.
NIS Maps [Toc] [Back]
Information distributed by NIS is stored in database files
called maps. Most of the NIS maps represent files that
were traditionally stored in the /etc directory. These
files include the following: aliases group hosts netgroups
networks passwd protocols rpc services
In a secure environment, you can run NIS in a secure mode,
thereby creating secure and nonsecure versions of the NIS
maps. See Security Administration for more information.
You can also use NIS to distribute files used by Automount
or AutoFS, or to distribute other user-defined files.
Each NIS map contains a set of keys and associated values.
For example, as keys, the hosts map contains all host
names on a network, and as values, the corresponding
Internet addresses. Each NIS map has a map name, used by
programs to access data in the map.
NIS Domains [Toc] [Back]
A named set of NIS maps is called a domain. A system's
"domain name" or "NIS domain" corresponds to the set of
NIS maps that the system can access. You can think of an
NIS domain as a set of systems that share the same set of
NIS maps.
A system's domain name is set at the time the system is
booted by the /sbin/init.d/nis script using an entry in
the /etc/rc.config.common file. System administrators can
use the nissetup script to place entries in this file.
The nissetup script is described in the Network Administration:
Services manual.
You can determine your system's NIS domain using the
domainname command. Refer to domainname(1). A domain name
is required for retrieving data from an NIS database.
NIS Client-Server Model [Toc] [Back]
NIS follows the client-server model of distributed services.
There are two types of NIS servers - master and
slave. The master server stores the master copy of the
NIS maps for its domain; these are the only NIS maps that
can be modified. Each domain has only one master server.
Slave servers store copies of the master server's NIS
maps. NIS slave servers can be spread throughout a
network. Whenever an NIS map is updated on the master
server, the master propagates the changes to each slave
server in its domain. If the master is unavailable for
any reason, the slave servers continue to make the NIS
maps available to the NIS clients.
Clients are all of the systems that can access NIS maps.
When a client requires NIS information, it makes a remote
procedure call (RPC) to one of the NIS servers to obtain
the information.
NIS Data Storage [Toc] [Back]
The data in NIS maps is stored as databases in dbm/ndbm,
btree, or hash format.
For example, the NIS map for the /etc/hosts file in the
domain market might be stored in these dbm/ndbm files:
/var/yp/market/hosts.byaddr.dir /var/yp/market/hosts.byaddr.pag
/var/yp/market/hosts.byname.dir
/var/yp/market/hosts.byname.pag
The makedbm command takes an ASCII file such as /etc/hosts
and converts it into dbm/ndbm files suitable for use by
NIS. However, system administrators use the Makefile
script in the /var/yp directory to create NIS map files
and specify file format. The Makefile script then calls
makedbm.
Refer to the Network Administration: Services manual for
details on the Makefile script, specifying different formats,
and other NIS management information.
Commands: domainname(1), svcsetup(8), ypbind(8), yppasswdd(8), ypserv(8), ypxfr(8)
Files: svc.conf(4)
Network Administration: Services
nis_intro(7)
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