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YPBIND(8)               FreeBSD System Manager's Manual              YPBIND(8)

     ypbind -- NIS domain binding daemon

     ypbind [-ypset] [-ypsetme] [-s] [-m] [-S domainname,server1,server2,...]

     The ypbind 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 domainname(1) command) using net-
     work broadcasts.  Once it receives a reply, it will store the address of
     the server and other information in a special file located in
     /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

     After a binding has been established, ypbind 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, ypbind assumes that the server
     is no longer running and resumes its network broadcasts until another
     binding is established.  The ypbind utility will also log warning mes-
     sages using the syslog(3) facility each time it detects that a server has
     stopped responding, as well as when it has bound to a new server.

     The following options are available:

     -ypset  It is possible to force ypbind to bind to a particular NIS server
             host for a given domain by using the ypset(8) command.  However,
             ypbind refuses YPBINDPROC_SETDOM requests by default since it has
             no way of knowing exactly who is sending them.  Using the -ypset
             flag causes ypbind 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.

             This is similar to the -ypset flag, except that it only permits
             YPBINDPROC_SETDOM requests to be processed if they originated
             from the local host.

     -s      Cause ypbind 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).

     -S domainname,server1,server2,server3,...
             Allow the system administrator to lock ypbind to a particular
             domain and group of NIS servers.  Up to ten servers can be speci-
             fied.  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 speci-
             fied 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 -ypset or -ypsetme options, which are often considered to be
             security holes.  The specified servers must have valid entries in
             the local /etc/hosts file.  IP addresses may be specified in
             place of hostnames.  If ypbind cannot make sense out of the argu-
             ments, it will ignore the -S flag and continue running normally.

             Note that ypbind will consider the domainname specified with the
             -S flag to be the system default domain.

     -m      Cause ypbind to use a 'many-cast' rather than a broadcast for
             choosing a server from the restricted mode server list.  In many-
             cast mode, ypbind 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 sub-
             nets where no local NIS servers are available.  The -m flag can
             only be used in conjunction with the -S flag above (if used with-
             out the -S flag, it has no effect).

     The ypbind utility will not make continuous attempts to keep secondary
     domains bound.  If a server for a secondary domain fails to respond to a
     ping, ypbind will broadcast for a new server only once before giving up.
     If a client program attempts to reference the unbound domain, ypbind will
     try broadcasting again.  By contrast, ypbind will automatically maintain
     a binding for the default domain whether client programs reference it ot

                   the files used to hold binding information for each NIS
     /etc/rc.conf  system configuration file where the system default domain
                   and ypbind startup options are specified

     domainname(1), syslog(3), yp(8), ypserv(8), ypset(8)

     Theo de Raadt <>

FreeBSD 6.2                      April 9, 1995                     FreeBSD 6.2


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