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YPFILES(5) YPFILES(5)
NAME
ypfiles - the yellowpages database and directory structure
DESCRIPTION
The yellow pages (YP) network lookup service uses a database of dbm
files in the directory hierarchy at /etc/yp . A dbm database consists
of two files, created by calls to the dbm(3X) 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 YP is called a YP map. A YP domain is a named
set of YP maps. Each YP domain is implemented as a subdirectory of
/etc/yp containing the map. Any number of YP domains can exist. Each
may contain any number of maps.
No maps are required by the YP 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 YP serves - if the map exists in a given
domain, and a client asks about it, the YP will serve it. For a map to
be accessible consistently, it must exist on all YP servers that serve
the domain. To provide data consistency between the replicated maps,
an entry to run ypxfr periodically should be made in /usr/lib/crontab
on each server. More information on this topic is in ypxfr(8).
YP maps should 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 should be the UNIX time in seconds when the
map was built. The second key is YP_MASTER_NAME, with the name of the
YP master server as a value. makedbm 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. In
addition, values of these two keys are used by ypxfr when it transfers
a map from a master YP 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.
YP maps must be generated and modified only at the master server. They
are copied to the slaves using ypxfr(8) to avoid potential byte-
ordering problems among YP servers running on machines with different
architectures, and to minimize the amount of disk space required for
the dbm files. The YP database can be initially set up for both
masters and slaves by using ypinit(8).
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 YP map and is propagated
from the master to the slaves by running /etc/yp/Makefile . If you add
a YP map, edit the this file to support the new map. The makefile uses
makedbm to generate the YP map on the master, and yppush to propagate
the changed map to the slaves. yppush is a client of the map ypservers
, which lists all the YP servers. For more information on this topic,
see yppush(8).
SEE ALSO
makedbm(8), ypinit(8), ypmake(8), ypxfr(8), yppush(8), yppoll(8),
ypserv(8), rpcinfo(8),
1 Aug 1985 YPFILES(5)
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