NFS Services Administrator's Guide

Configuring and Administering NIS+
Overview of NIS+
Chapter 5 205
just hosts.org_dir or [cname=romney],hosts.org_dir. Domain
names always end in a period, except when you are setting the default
domain with the domainname command.
How NIS+ Information is Stored and Propagated
NIS+ information is stored in the /var/nis directory. On a server, the
/var/nis/data subdirectory, or the /var/nis/hostname subdirectory
(where hostname is the name of the local host), contains the NIS+
directories and tables that make up the domain.
You can make changes to the NIS+ objects from any NIS+ client in the
namespace, if you are authenticated and have the proper access
permissions. Whenever anyone makes a change to an NIS+ object, the
change is sent to all the replica servers. NIS+ sends only the changes to
replica servers, not whole tables. A transaction log in the /var/nis
directory on each server keeps track of all the changes that have been
made. To keep the transaction log from growing too large, you must
checkpoint the domain regularly. When you checkpoint the domain
(with the nisping[1M] command), the changes in the transaction log on
all the servers are incorporated into the tables on disk, and the
transaction log is cleared.
An NIS+ client may get information from any domain in the namespace,
if it is authenticated and has the proper access permissions. Each NIS+
client has a file called NIS_COLD_START in the /var/nis directory, which
contains the internet addresses of servers the client can contact for NIS+
information. Because all servers are also clients, every server has a cold
start file, too. An NIS+ client does not “bind” to a server the way an NIS
client does. It contacts a server directly to request information. If a client
requests information about a domain from a server that does not serve
the domain, the server tells the client how to find a server that serves the
domain. As the client learns about other servers, it adds the information
to a cache file called NIS_SHARED_DIRCACHE in the /var/nis directory,
and it uses the information to find servers later.