mDNSShared/mDNSResponder.8

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  17 .Dd April 2004              \" Date
  18 .Dt mDNSResponder 8         \" Document Title
  19 .Os Darwin                  \" Operating System
  20 .\"
  21 .Sh NAME
  22 .Nm mDNSResponder
  23 .Nd Multicast and Unicast DNS daemon    \" Name Description for whatis database
  24 .\"
  25 .Sh SYNOPSIS
  26 .Nm
  27 .\"
  28 .Sh DESCRIPTION
  29 .Nm
  30 (also known as
  31 .Nm mdnsd
  32 on some systems)
  33 is a daemon invoked at boot time to implement Multicast DNS and DNS Service Discovery. On
  34 Mac OS X 10.6 (Snow Leopard),
  35 .Nm
  36 is also the system-wide Unicast DNS Resolver.
  37 .Pp
  38 .Nm
  39 listens on UDP port 5353 for Multicast DNS Query packets.
  40 When it receives a query for which it knows an answer,
  41 .Nm
  42 issues the appropriate Multicast DNS Reply packet.
  43 .Pp
  44 .Nm
  45 also performs Unicast and Multicast DNS Queries on behalf of client processes, and
  46 maintains a cache of the replies.
  47 .Pp
  48 .Nm
  49 has no user-specifiable command-line argument, and users should not run
  50 .Nm
  51 manually.
  52 .Pp
  53 .Sh LOGGING
  54 There are several methods with which to examine
  55 .Nm Ns 's internal state for debugging and diagnostic purposes. The syslog(1)
  56 logging levels map as follows:
  57 .Pp
  58 .Dl Error - Error messages
  59 .Dl Warning - Client-initiated operations
  60 .Dl Notice - Sleep proxy operations
  61 .Dl Info - Informational messages
  62 .Pp
  63 By default, only log level Error is logged.
  64 .Pp
  65 A SIGUSR1 signal toggles additional logging, with Warning and Notice
  66 enabled by default:
  67 .Pp
  68 .Dl % sudo killall -USR1 mDNSResponder
  69 .Pp
  70 Once this logging is enabled, users can additionally use syslog(1)
  71 to change the log filter for the process. For example, to enable log levels Emergency - Debug:
  72 .Pp
  73 .Dl % sudo syslog -c mDNSResponder -d
  74 .Pp
  75 A SIGUSR2 signal toggles packet logging:
  76 .Pp
  77 .Dl % sudo killall -USR2 mDNSResponder
  78 .Pp
  79 A SIGINFO signal will dump a snapshot summary of the internal state to
  80 .Pa /var/log/system.log Ns :
  81 .Pp
  82 .Dl % sudo killall -INFO mDNSResponder
  83 .Sh OPTIONAL ARGUMENTS
  84 .Nm
  85 accepts the following optional arguments:
  86 .Bl -tag -width "AlwaysAppendSearchDomains"
  87 .It Fl AlwaysAppendSearchDomains
  88 Append search domains for multi-labeled Partially Qualified Domain Name as well as single-labeled Partially Qualified Domain Name.
  89 This argument is not recommended because of the extra DNS traffic it generates and its adverse effect on battery life.
  90 .It Fl NoMulticastAdvertisements
  91 Prevent the system from advertising Bonjour services via Multicast DNS.
  92 .El
  93 .Pp
  94 To cause
  95 .Nm
  96 to run with these optional arguments when it launches on OS X 10.11 (El Capitan) and later, set the
  97 .Sy AlwaysAppendSearchDomains
  98 or
  99 .Sy NoMulticastAdvertisements
 100 boolean keys to true in /Library/Preferences/com.apple.mDNSResponder.plist and reboot.
 101 .Pp
 102 .Sh FILES
 103 .Pa /usr/sbin/mDNSResponder
 104 .Pa /Library/Preferences/com.apple.mDNSResponder.plist
 105 .Pp
 106 .Sh INFO
 107 .Pp
 108 For information on Multicast DNS, see
 109 .Pa http://www.multicastdns.org/
 110 .Pp
 111 For information on DNS Service Discovery, see
 112 .Pa http://www.dns-sd.org/
 113 .Pp
 114 For information on how to use the Multicast DNS and the
 115 DNS Service Discovery APIs on Mac OS X and other platforms, see
 116 .Pa http://developer.apple.com/bonjour/
 117 .Pp
 118 For the source code to
 119 .Nm , see
 120 .Pa http://developer.apple.com/darwin/projects/bonjour/
 121 .\"
 122 .Sh BUGS
 123 .Nm
 124 bugs are tracked in Apple Radar component "mDNSResponder".
 125 .\"
 126 .Sh HISTORY
 127 The
 128 .Nm
 129 daemon first appeared in Mac OS X 10.2 (Jaguar).
 130 .Pp
 131 Also available from the Darwin open source repository
 132 (though not officially supported by Apple) are
 133 .Nm
 134 daemons for other platforms, including Microsoft Windows,
 135 Linux, FreeBSD, NetBSD, Solaris, and other POSIX systems.