ypfiles(4) ypfiles(4)
NAME
ypfiles - NIS database and directory structure
DESCRIPTION
The Network Information Service (NIS) uses a distributed,
replicated database of dbm files contained in the /var/yp
directory hierarchy on each NIS server. A dbm database
consists of two files, one has the filename extension .pag and
the other has the filename extension .dir. For instance, the
database named publickey is implemented by the pair of files
publickey.pag and publickey.dir.
A dbm database served by the NIS is called an NIS map. An NIS
domain is a subdirectory of /var/yp containing a set of NIS
maps. Any number of NIS domains can exist. Each domain may
contain any number of maps.
Files
/var/yp
/var/yp/aliases
/var/yp/Makefile
USAGE
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, 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 privileged user's crontab file on each server. For more
information on this topic, see ypxfr(1M).
NIS maps contain two distinguished key-value pairs. The first
is the key YP_LAST_MODIFIED, having as a value a ten-character
ASCII order number. The order number indicates the system
time in seconds when the map was built. The second key is
YP_MASTER_NAME, 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 NIS, 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
Copyright 1994 Novell, Inc. Page 1
ypfiles(4) ypfiles(4)
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,
extra command line switches must be set when it is run.
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).
All NIS maps have entries in /var/yp/aliases. Each entry
includes the map name and a map nickname. The map name and
nickname may be the same depending on the filesystem
limitation of the length of filenames.
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 a standard text editor. The update is
incorporated into the NIS map and is propagated from the
master to the slaves by running /var/yp/Makefile. See
ypbuild(1M). All system-supplied maps have entries in
/var/yp/Makefile; if an NIS map is added, 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).
REFERENCES
dbm(3N), domainname(1M), makedbm(1M), ypbuild(1M), ypinit(1M),
yppasswdd(1M), yppoll(1M), yppush(1M), ypserv(1M), ypxfr(1M)
Copyright 1994 Novell, Inc. Page 2