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mDNSResponder(8)	     System Manager's Manual		mDNSResponder(8)

NAME
     mDNSResponder -- Multicast and Unicast DNS daemon

SYNOPSIS
     mDNSResponder

DESCRIPTION
     mDNSResponder  (also known as mdnsd on some systems) is a daemon invoked at
     boot time to implement Multicast DNS and DNS Service Discovery. On Mac OS X
     10.6 (Snow Leopard), mDNSResponder is also the system-wide Unicast DNS  Re-
     solver.

     mDNSResponder  listens  on  UDP  port 5353 for Multicast DNS Query packets.
     When it receives a query for which it knows an answer, mDNSResponder issues
     the appropriate Multicast DNS Reply packet.

     mDNSResponder also performs Unicast and Multicast DNS Queries on behalf  of
     client processes, and maintains a cache of the replies.

     mDNSResponder  has  no  user-specifiable  command-line  argument, and users
     should not run mDNSResponder manually.

LOGGING
     There are several methods with which to  examine  mDNSResponder's	internal
     state  for  debugging and diagnostic purposes. The syslog(1) logging levels
     map as follows:

	   Error - Error messages
	   Warning - Client-initiated operations
	   Notice - Sleep proxy operations
	   Info - Informational messages

     By default, only log level Error is logged.

     A SIGUSR1 signal toggles additional logging, with Warning	and  Notice  en-
     abled by default:

	   % sudo killall -USR1 mDNSResponder

     Once  this  logging  is  enabled,	users  can additionally use syslog(1) to
     change the log filter for the process. For example, to  enable  log  levels
     Emergency - Debug:

	   % sudo syslog -c mDNSResponder -d

     A SIGUSR2 signal toggles packet logging:

	   % sudo killall -USR2 mDNSResponder

     A	SIGINFO  signal  will  dump  a snapshot summary of the internal state to
     /var/log/system.log:

	   % sudo killall -INFO mDNSResponder

OPTIONAL ARGUMENTS
     mDNSResponder accepts the following optional arguments:

     -AlwaysAppendSearchDomains
				Append search  domains	for  multi-labeled  Par-
				tially	Qualified Domain Name as well as single-
				labeled Partially Qualified Domain  Name.   This
				argument is not recommended because of the extra
				DNS  traffic it generates and its adverse effect
				on battery life.

     -NoMulticastAdvertisements
				Prevent the system from advertising Bonjour ser-
				vices via Multicast DNS.

     To cause mDNSResponder  to  run  with  these  optional  arguments	when  it
     launches	 on   OS   X   10.11   (El   Capitan)	and   later,   set   the
     AlwaysAppendSearchDomains or NoMulticastAdvertisements boolean keys to true
     in /Library/Preferences/com.apple.mDNSResponder.plist and reboot.

FILES
     /usr/sbin/mDNSResponder /Library/Preferences/com.apple.mDNSResponder.plist

INFO
     For information on Multicast DNS, see http://www.multicastdns.org/

     For information on DNS Service Discovery, see http://www.dns-sd.org/

     For information on how to use the Multicast DNS and the DNS Service Discov-
     ery    APIs    on	  Mac	 OS    X    and     other     platforms,     see
     http://developer.apple.com/bonjour/

     For       the	 source       code	 to	 mDNSResponder,      see
     http://developer.apple.com/darwin/projects/bonjour/

BUGS
     mDNSResponder bugs are tracked in Apple Radar component "mDNSResponder".

HISTORY
     The mDNSResponder daemon first appeared in Mac OS X 10.2 (Jaguar).

     Also available from the Darwin open source  repository  (though  not  offi-
     cially  supported	by Apple) are mDNSResponder daemons for other platforms,
     including Microsoft Windows, Linux, FreeBSD,  NetBSD,  Solaris,  and  other
     POSIX systems.

Darwin				   April 2004			mDNSResponder(8)
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