ypfiles(4N) ypfiles(4N)
NAME
ypfiles - the YP database and directory structure
DESCRIPTION
The YP network lookup service uses a distributed, replicated database
of dbm files contained in the /var/yp directory hierarchy on each YP
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 YP is called a YP map. A YP ypdomain is
a subdirectory of /var/yp containing a set of YP maps. 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 the privileged user's crontab file on each server. More
information on this topic is in ypxfr(1M).
YP 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 YP 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 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, extra command line switches must be set
when it is run.
YP 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 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(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
a standard text editor. The update is incorporated into the YP map
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and is propagated from the master to the slaves by running
/var/yp/Makefile, see ypmake(1M). All Sun-supplied maps have entries
in /var/yp/Makefile; if a YP map is added, edit this file to support
the new map. The makefile uses makedbm(1M) to generate the YP 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
YP servers. For more information on this topic, see yppush(1M).
FILES
/var/yp
/var/yp/aliases
/var/yp/Makefile
SEE ALSO
makedbm(1M), ypinit(1M), ypmake(1M), yppoll(1M), yppush(1M),
ypserv(1M), ypxfr(1M), dbm(3), publickey(4)
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