4.3BSD-UWisc/man/man5/ypfiles.5

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.\" @(#)ypfiles.5 1.1 85/12/28 SMI; 
.TH YPFILES 5 "1 Aug 1985"
.SH NAME
ypfiles \- the yellowpages database and directory structure
.SH DESCRIPTION
.IX  "ypfiles file"  ""  "\fLypfiles\fP \(em yellowpages database and directory"
The yellow pages (YP) network lookup service uses a database of
.I dbm
files in the directory hierarchy at
.I /etc/yp .
A
.I dbm
database consists of two files, created by calls to the
.IR dbm (3X)
library package.  One has the filename extension
.I .pag
and the other has the filename extension
.IR .dir .
For instance, the database named
.IR hosts.byname ,
is implemented by the pair of files
.I hosts.byname.pag
and
.IR hosts.byname.dir .
A
.I dbm
database served by the YP is called a YP 
.IR map .
A YP
.I domain
is a named set of YP maps.  
Each YP domain is implemented as a subdirectory of
.I /etc/yp 
containing the map.
Any number of YP domains can exist.  Each may contain any number of 
maps.
.LP
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 
.I ypxfr
periodically should be made in
.I /usr/lib/crontab
on each server.  More information on this topic is in ypxfr(8).
.LP
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 \s-2UNIX\s0 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.  
.IR 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 
.I 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
.I ypxfr 
when it transfers a map from a master YP server to a slave.  
If 
.I 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.
.LP
YP maps must be generated and modified only at the master server.  They
are copied to the slaves using 
.IR 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
.IR ypinit (8).
.LP
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 
.I /etc/yp/Makefile .
All Sun-supplied maps have entries in 
.I /etc/yp/Makefile ;
if you add a YP map, edit the this file to support the new map.
The makefile uses 
.I makedbm 
to generate the YP map on the master, and
.I yppush 
to propagate the changed map to the slaves.  
.I yppush
is a client of the map
.I ypservers ,
which lists all the YP servers.  
For more information on this topic, see yppush(8).
.SH "SEE ALSO"
makedbm(8), ypinit(8), ypmake(8), ypxfr(8), yppush(8), yppoll(8), 
ypserv(8), rpcinfo(8),