.\" Copyright (c) 1995, 1996
.\"	Bill Paul <wpaul@ctr.columbia.edu>.  All rights reserved.
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.Dd June 2, 1996
.Dt RPC.YPXFRD 8
.Os
.Sh NAME
.Nm rpc.ypxfrd
.Nd "NIS map transfer server"
.Sh SYNOPSIS
.Nm
.Op Fl p Ar path
.Sh DESCRIPTION
The
.Nm
utility is used to speed up the distribution of very large NIS maps
from NIS master to NIS slave servers.
The normal method for transferring
maps involves several steps:
.Bl -bullet -offset indent
.It
The master server calls
.Xr yppush 8
to inform the slave servers to start a transfer.
.It
The slave servers invoke
.Xr ypxfr 8 ,
which reads the entire contents of a map from the master server
using the yp_all() function.
.It
The
.Xr ypxfr 8
program then creates a new map database file by using the
.Xr db 3
library hash method to store the data that it receives from the server.
.It
When all the data has been retrieved,
.Xr ypxfr 8
moves the new file into place and sends
.Xr ypserv 8
on the local machine a YPPROC_CLEAR to tell it to refresh its
database handles.
.El
.Pp
This process can take several minutes when there are very large
maps involved.
For example: a passwd database with several tens of
thousands of entries can consume several megabytes of disk space,
and it can take the
.Xr db 3
library package a long time to sort and store all the records
in a hash database.
Consider also that there are two sets of map
files:
.Pa master.passwd.by{name,uid}
and
.Pa passwd.by{name,uid} .
.Pp
The
.Nm
utility speeds up the transfer process by allowing NIS slave servers to
simply copy the master server's map files rather than building their
own from scratch.
Simply put,
.Nm
implements an RPC-based file transfer protocol.
Transferring even
a multi-megabyte file in this fashion takes only a few seconds compared
to the several minutes it would take even a reasonably fast slave server
to build a new map from scratch.
.Pp
The
.Nm
utility uses the same access restriction mechanism as
.Xr ypserv 8 .
This means that slave servers will only be permitted to transfer
files if the rules in the
.Pa securenets
database permit it (see
.Xr ypserv 8
for more information on
.Pa securenets ) .
Furthermore, only slave servers using reserved
ports will be allowed to transfer the
.Pa master.passwd
maps.
.Sh OPTIONS
The following option is available:
.Bl -tag -width indent
.It Fl p Ar path
This option can be used to override the default path to
the location of the NIS
map databases.
The compiled-in default path is
.Pa /var/yp .
.El
.Sh FILES
.Bl -tag -width Pa -compact
.It Pa /var/yp/[domainname]/[maps]
The NIS maps for a particular NIS domain.
.El
.Sh SEE ALSO
.Xr yp 8 ,
.Xr yppush 8 ,
.Xr ypserv 8 ,
.Xr ypxfr 8
.Sh AUTHORS
.An Bill Paul Aq Mt wpaul@ctr.columbia.edu
.Sh BUGS
The
.Fx
.Nm ypxfrd
protocol is not compatible with that used by SunOS.
This is unfortunate
but unavoidable: Sun's protocol is not freely available, and even if it
were it would probably not be useful since the SunOS NIS v2 implementation
uses the original ndbm package for its map databases whereas the
.Fx
implementation uses Berkeley DB.
These two packages use vastly different
file formats.
Furthermore, ndbm is byte-order sensitive and not very
smart about it, meaning that am ndbm database created on a big endian
system cannot be read on a little endian system.