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mDNSResponder(8)	  BSD 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 Resolver.

     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
     enabled 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

FILES
     /usr/sbin/mDNSResponder

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 Dis‐
     covery 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 Mac OS 9, Microsoft Windows, Linux, FreeBSD, NetBSD, Solaris,
     and other POSIX systems.

Darwin				April 27, 2024				Darwin

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