freebsd/libexec/ypxfr/ypxfr.8

.\" Copyright (c) 1995
.\"	Bill Paul <wpaul@ctr.columbia.edu>.  All rights reserved.
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.Dd February 5, 1995
.Dt YPXFR 8
.Os
.Sh NAME
.Nm ypxfr
.Nd "transfer NIS database from remote server to local host"
.Sh SYNOPSIS
.Nm ypxfr
.Op Fl f
.Op Fl c
.Op Fl d Ar target domain
.Op Fl h Ar source host
.Op Fl s Ar source domain
.Op Fl p Ar path
.Op Fl C Ar taskid program-number ipaddr port
.Ar mapname
.Sh DESCRIPTION
.Nm ypxfr
copies an NIS database (or
.Pa map )
from one NIS server to another using NIS services. In FreeBSD,
.Nm ypxfr
is generally invoked by
.Xr ypserv 8
when it receives a map transfer request from
.Xr yppush 8 .
.Nm ypxfr
is used primarily in environments where several NIS servers
are in use in a single domain. One server, the NIS master, maintains
the canonical copies of all NIS maps, and all the other servers,
the NIS slaves, copy new versions of the maps from the master whenever
any updates are made (i.e. when a user updates their password via
.Xr yppasswd 1
).
.Pp
When run,
.Nm ypxfr
creates a temporary database file in
.Pa /var/yp/[domainmame] ,
and fills it with the contents of
.Ar mapname
as supplied by the specified
.Ar source host .
When the entire map has been transfered,
.Nm ypxfr
deletes the original copy of
.Ar mapname
and moves the temporary copy into its place. When the transfer is
complete,
.Nm ypxfr
will attempt to send a 'clear current map' request to the local
.Xr ypserv 8
process to clear any possible references it may still have to the
stale map.
.Pp
Note that all files created by
.Nm ypxfr
are owner readable and writable only for security reasons. Since the
NIS maps and the directory in which they reside are normally owned by
root, this prevents non-privleged users from making unauthorized
modifications.
.Pp
In order to maintain consistency across all NIS servers,
.Nm ypxfr
can be run periodically in a
.Xr cron 8
job. Maps which change infrequently
need only be updated once a day (preferably late at night when system
usage is lowest), whereas those that are subject to frequent changes
(such a
.Pa passwd.byname
and
.Pa passwd.byuid )
should be updated perhaps once every hour. Using
.Xr cron 8
to automatically
update the NIS maps is not strictly mandatory since all updates should
be propagated by
.Xr yppush 8
when
.Pa /var/yp/Makefile
is run on the NIS master server, however it is good practice
on large networks where possible outages could cause NIS servers to
fall out of sync with each other.
.Pp
When
.Nm ypxfr
is invoked without a controlling terminal, e.g. from inside
.Xr ypserv 8 ,
it logs all its output using the
.Xr syslog 3
facility.
.Sh NOTES
The FreeBSD version of
.Nm ypxfr
has support for a special map transfer protocol which works in
conjunction with the FreeBSD
.Xr rpc.ypxfrd 8
server. This protocol allows it to transfer raw map database files from
the NIS master server and can be many times faster than the standard
transfer method, particularly for very large NIS maps. The
.Nm ypxfr
command will check to see if the
.Xr rpc.ypxfrd 8
server is registered on the NIS master server and attempt to use
it if it is present. If it isn't it will fall back to the standard
transfer method, copying the map contents from
.Xr ypserv 8
and creating new maps instead.
.Pp
Note that while the FreeBSD ypxfrd protocol is conceptually similar
to the SunOS ypxfrd protocol, FreeBSD's protocol is not compatible with
Sun's, therefore it will not work with Sun's ypxfrd server. FreeBSD
slave systems can still transfer maps from any non-FreeBSD NIS server,
however they will only be able to take advantage of the faster protocol
if the master server is also running FreeBSD.
.Sh OPTIONS
The following options and flags are supported by
.Nm ypxfr :
.Bl -tag -width flag
.It Fl f
Force a map transfer. Normally,
.Nm ypxfr
will not transfer a map if it determines that the NIS master's copy
is not newer than the existing copy already on the local host: the
.Fl f
flag forces a transfer regardless of which server's version is more recent.
.It Fl c
Do not send a 'clear current map' request to the
.Xr ypserv 8
process running on the local host. This flag is normally used when
invoking
.Nm ypxfr
manually on a machine that is not yet running
.Xr ypserv 8 .
Without this flag, failure to contact the local NIS server will cause
.Nm ypxfr
to abort the transfer.
.It Fl d Ar target domain
Specify a target domain other than the current NIS domain.
.It Fl h Ar source host
Specify the name of the host from which to copy the NIS maps. This option
is used to insure that
.Nm ypxfr
only copies maps from the NIS master server.
.It Fl s Ar source domain
Specify the domain from which to transfer a map, in the event that
the transfer is being done across two different NIS domains.
.It Fl p Ar path
Specify the top level directory containing the NIS maps. By
default, this path is
.Pa /var/yp .
The
.Fl p
flag allows you to specify an alternate path should you wish to
store your NIS maps in a different part of the filesystem. The
NIS server,
.Xr ypserv 8 ,
passes this flag to
.Nm ypxfr
if it too has been told to use an alternate path.
.It Fl C Ar taskid program-number ipaddr port
These options are used only when
.Nm ypxfr
is invoked by
.Xr ypserv 8
in response to a map transfer request initiated by
.Xr yppush 8 .
In this instance,
.Nm ypxfr
needs to 'callback' to the
.Xr yppush 8
process and interact with it, so
.Xr yppush 8
passes to it an IP address
.Ar ipaddr ,
port number
.Ar port ,
registered program number
.Ar program-number
and a transaction ID
.Ar taskid
that it can use to contact the waiting
.Xr yppush 8
process on the master server.
.It Ar mapname
The name of the map to transfer.
.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 4 ,
.Xr yppush 8 ,
.Xr ypserv 8
.Sh AUTHOR
Bill Paul <wpaul@ctr.columbia.edu>