YPFILES(5)              COMMAND REFERENCE              YPFILES(5)



NAME
     ypfiles - the Yellow Pages data base and directory structure

DESCRIPTION
     The Yellow Pages (YP) network lookup service uses a data
     base of dbm files in the directory hierarchy at /etc/yp.  A
     dbm data base consists of two files, created by calls to the
     dbm(3d) library package; one has the file name extension
     .pag and the other has the file name extension .dir.  For
     instance, the data base named hosts.byname, is implemented
     by the pair of files hosts.byname.pag and hosts.byname.dir.
     A dbm data base 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 UNIXr 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 data base can be initially set up for both
     masters and slaves by using ypinit(8).



Printed 3/13/89                                                 1

YPFILES(5)              COMMAND REFERENCE              YPFILES(5)



     After the server data bases are set up, it is probable that
     the contents of some maps will change.  In general, some
     ASCII source version of the data base exists on the master,
     and it is changed using a standard text editor.  The update
     is incorporated into the YP map and is propagated from the
     master to the slaves by accessing the /etc/yp file and
     running make mapname; if you add a YP map, edit the makefile
     to support the new map.  The makefile uses makedbm to
     generate the YP map on the master; yppush pushes the new
     version of the map to slave servers, using the ypserver map
     for information, (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), and rpcinfo(8).






































Printed 3/13/89                                                 2

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