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.\" $FreeBSD$
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.Dd April 9, 1995
.Dt YPBIND 8
.Os
.Sh NAME
.Nm ypbind
.Nd "NIS domain binding daemon"
.Sh SYNOPSIS
.Nm
.Op Fl ypset
.Op Fl ypsetme
.Op Fl s
.Op Fl m
.Oo
.Fl S
.Sm off
.Ar domainname , server1 , server2 , ...
.Sm on
.Oc
.Sh DESCRIPTION
The
.Nm
utility is the process that maintains NIS binding information.
At startup,
it searches for an NIS server responsible for serving the system's
default domain (as set by the
.Xr domainname 1
command) using network broadcasts.
Once it receives a reply,
it will store the address of the server and other
information in a special file located in
.Pa /var/yp/binding .
The NIS routines in the standard C library can then use this file
when processing NIS requests.
There may be several such files
since it is possible for an NIS client to be bound to more than
one domain.
.Pp
After a binding has been established,
.Nm
will send DOMAIN_NONACK requests to the NIS server at one minute
intervals.
If it fails to receive a reply to one of these requests,
.Nm
assumes that the server is no longer running and resumes its network
broadcasts until another binding is established.
The
.Nm
utility will also log warning messages using the
.Xr syslog 3
facility each time it detects that a server has stopped responding,
as well as when it has bound to a new server.
.Pp
The following options are available:
.Bl -tag -width indent
.It Fl ypset
It is possible to force
.Nm
to bind to a particular NIS server host for a given domain by using the
.Xr ypset 8
command.
However,
.Nm
refuses YPBINDPROC_SETDOM requests by default since it has no way of
knowing exactly who is sending them.
Using the
.Fl ypset
flag causes
.Nm
to accept YPBINDPROC_SETDOM requests from any host.
This option should only
be used for diagnostic purposes and only for limited periods since allowing
arbitrary users to reset the binding of an NIS client poses a severe
security risk.
.It Fl ypsetme
This is similar to the
.Fl ypset
flag, except that it only permits YPBINDPROC_SETDOM requests to be processed
if they originated from the local host.
.It Fl s
Cause
.Nm
to run in secure mode: it will refuse to bind to any NIS server
that is not running as root (i.e., that is not using privileged
TCP ports).
.It Fl S Xo
.Sm off
.Ar domainname , server1 , server2 , server3 , ...
.Sm on
.Xc
Allow the system administrator to lock
.Nm
to a particular
domain and group of NIS servers.
Up to ten servers can be specified.
There must not be any spaces between the commas in the domain/server
specification.
This option is used to insure that the system binds
only to one domain and only to one of the specified servers, which
is useful for systems that are both NIS servers and NIS
clients: it provides a way to restrict what machines the system can
bind to without the need for specifying the
.Fl ypset
or
.Fl ypsetme
options, which are often considered to be security holes.
The specified
servers must have valid entries in the local
.Pa /etc/hosts
file.
IP addresses may be specified in place of hostnames.
If
.Nm
can't make sense out of the arguments, it will ignore
the
.Fl S
flag and continue running normally.
.Pp
Note that
.Nm
will consider the domainname specified with the
.Fl S
flag to be the system default domain.
.It Fl m
Cause
.Nm
to use a 'many-cast' rather than a broadcast for choosing a server
from the restricted mode server list.
In many-cast mode,
.Nm
will transmit directly to the YPPROC_DOMAIN_NONACK procedure of the
servers specified in the restricted list and bind to the server that
responds the fastest.
This mode of operation is useful for NIS clients on remote subnets
where no local NIS servers are available.
The
.Fl m
flag can only be used in conjunction with the
.Fl S
flag above (if used without the
.Fl S
flag, it has no effect).
.El
.Sh NOTES
The
.Nm
utility will not make continuous attempts to keep secondary domains bound.
If a server for a secondary domain fails to respond to a ping,
.Nm
will broadcast for a new server only once before giving up.
If a
client program attempts to reference the unbound domain,
.Nm
will try broadcasting again.
By contrast,
.Nm
will automatically maintain a binding for the default domain whether
client programs reference it ot not.
.Sh FILES
.Bl -tag -width /etc/rc.conf -compact
.It Pa /var/yp/binding/[domainname].[version]
the files used to hold binding information for each NIS domain
.It Pa /etc/rc.conf
system configuration file where the system default domain and
ypbind startup options are specified
.El
.Sh SEE ALSO
.Xr domainname 1 ,
.Xr syslog 3 ,
.Xr yp 8 ,
.Xr ypserv 8 ,
.Xr ypset 8
.Sh AUTHORS
.An Theo de Raadt Aq deraadt@fsa.ca