ypfiles(4)ypfiles(4)NAMEypfiles - Network Information Service (NIS) database and directory
structure
DESCRIPTION
The NIS database lookup service uses a database of dbm/ndbm, btree, or
hash files in the /var/yp directory hierarchy. A dbm/ndbm database
consists of two files created by calls to the dbminit(3) function. One
has the filename extension .pag and the other has the filename exten‐
sion .dir. For instance, the database named hosts.byname, is imple‐
mented by the pair of files hosts.byname.pag and hosts.byname.dir. A
btree or hash database consists of a single file created by calls to
the dbopen(3) function. A btree file has the filename extension
.btree; a hash file has the extension .hash.
A dbm/ndbm database served by NIS is called an NIS map. A NIS domain
is a named set of NIS maps. Each NIS domain is implemented as a subdi‐
rectory of /var/yp containing the maps. The number of NIS domains that
can exist is unlimited. Each domain can contain any number of maps.
The NIS maps are not required by the NIS lookup service, although they
may be required for the normal operation of other parts of the system.
The NIS lookup service serves all maps. If the map exists in a given
domain and a client asks about it, NIS will serve it. There is, how‐
ever, a set of default maps that the NIS service serves. The files
representing these maps are listed in this description under Files.
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 execute the ypxfr command periodically
should be made in the /var/spool/cron/crontab/root file on each slave
server. More information on this topic is in ypxfr(8). An entry in
the /var/spool/cron/crontab/root file must not exist, either on a NIS
master server or on a pure NIS client machine.
The NIS maps should contain two distinguished key-value pairs. The
first is the key YP_LAST_MODIFIED, whose value is a 10-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 NIS master server as a value. The makedbm(8) command generates
both key-value pairs automatically. A map that does not contain both
key-value pairs can be served by the NIS, but the ypserv process will
not be able to return values for ``Get order number'' or ``Get master
name'' requests. In addition, the values of these two keys are used by
ypxfr(8) when it transfers a map from a master NIS server to a slave.
Before they can be properly accessed, the NIS maps must be initially
set up for both masters and slaves by using the ypsetup(8) function.
Further, NIS maps must be generated and modified only at the master
server location. Copies of the master server NIS maps can then be
transferred to the slave servers using the ypxfr(8) function. If ypxfr
is unable to determine a map's location, or if it is unable to deter‐
mine whether the local copy is more recent than the master copy, extra
command line switches must be set when it is executed.
After the server databases are set up, the contents of some maps may
change. In general, some ASCII source version of the database exists
on the master. This version should be 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. All maps
must have entries in /var/yp/Makefile. If an NIS map is added, the
/var/yp/Makefile must be edited to support the new map. The makefile
uses makedbm(8) to generate the NIS map on the master, and yppush(8) to
propagate the changed map to the slaves. The yppush(8) command is a
client of the map ypservers, which lists all of the NIS servers.
FILES
/var/yp/src/passwd
/var/yp/src/group
/var/yp/src/hosts
/var/yp/src/networks
/var/yp/src/services
/var/yp/src/protocols
/var/yp/src/netgroup
RELATED INFORMATION
Commands: makedbm(8), rpcinfo(8), ypmake(8), yppoll(8), yppush(8),
ypserv(8), ypsetup(8), ypxfr(8).
Functions: btree(3), dbm(3), hash(3), ndbm(3). delim off
ypfiles(4)
