ypfiles(4) NFS 5.4R3.00 ypfiles(4)
NAME
ypfiles - the Network Information Service database and directory
structure
DESCRIPTION
The Network Information Service (NIS) network lookup service uses a
distributed, replicated database of dbm files contained in the
/etc/yp directory hierarchy on each NIS server. A dbm database
consists of two files, created by calls to the ndbm(3C) library
package. One has the filename extension .pag and the other has the
filename extension .dir. For instance, the database named
hosts.byname, is implemented by the pair of files hosts.byname.pag
and hosts.byname.dir.
A dbm database served by the NIS is called an NIS map. An NIS domain
is a subdirectory of /etc/yp containing a set of NIS maps. Any
number of NIS domains can exist. Each may contain any number of
maps.
No maps are required by the NIS lookup service itself, although they
may be required for the normal operation of other parts of the
system. There is no list of maps which NIS serves -- if the map
exists in a given domain, and a client asks about it, the NIS will
serve it. For a map to be accessible consistently, it must exist on
all NIS servers that serve the domain. To provide data consistency
between the replicated maps, an entry to run ypxfr periodically
should be made in the super-user's crontab file on each server. More
information on this topic is in ypxfr(1M).
NIS maps should contain two distinguished key-value pairs. The first
is the key YPLASTMODIFIED, having as a value a ten-character ASCII
order number. The order number should be the system time in seconds
when the map was built. The second key is YPMASTERNAME, with the
name of the NIS master server as a value. makedbm(1M) generates both
key-value pairs automatically. A map that does not contain both key-
value pairs can be served by the YP, but the ypserv process will not
be able to return values for ``Get order number'' or ``Get master
name'' requests. See ypserv(1M). In addition, values of these two
keys are used by ypxfr when it transfers a map from a master NIS
server to a slave. If ypxfr cannot figure out where to get the map,
or if it is unable to determine whether the local copy is more recent
than the copy at the master, you must set extra command line switches
when you run it.
NIS maps must be generated and modified only at the master server.
They are copied to the slaves using ypxfr(1M) to avoid potential
byte-ordering problems among NIS servers running on machines with
different architectures, and to minimize the amount of disk space
required for the dbm files. The NIS database can be initially set up
for both masters and slaves by using ypinit(1M).
After the server databases are set up, it is probable that the
contents of some maps will change. In general, some ASCII source
version of the database exists on the master, and it is changed with
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ypfiles(4) NFS 5.4R3.00 ypfiles(4)
a standard text editor. The update is incorporated into the NIS map
and is propagated from the master to the slaves by running
/etc/yp/Makefile. All maps supplied with this OS have entries in
/etc/yp/Makefile; if you add an NIS map, edit this file to support
the new map. The makefile uses makedbm(1M) to generate the NIS map
on the master, and yppush(1M) to propagate the changed map to the
slaves. yppush is a client of the map ypservers, which lists all the
NIS servers. For more information on this topic, see yppush(1M).
FILES
/etc/yp
/etc/yp/Makefile
SEE ALSO
makedbm(1M), rpcinfo(1M), ypinit(1M), ypmake(1M), yppoll(1M),
yppush(1M), ypserv(1M), ypxfr(1M), dbm(3X).
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