1.\" -*- tab-width: 4 -*- 2.\" 3.\" Copyright (c) 2003-2012 Apple Inc. All Rights Reserved. 4.\" 5.\" Licensed under the Apache License, Version 2.0 (the "License"); 6.\" you may not use this file except in compliance with the License. 7.\" You may obtain a copy of the License at 8.\" 9.\" http://www.apache.org/licenses/LICENSE-2.0 10.\" 11.\" Unless required by applicable law or agreed to in writing, software 12.\" distributed under the License is distributed on an "AS IS" BASIS, 13.\" WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 14.\" See the License for the specific language governing permissions and 15.\" limitations under the License. 16.\" 17.Dd Feb 25, 2018 \" 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 32on some systems) 33is a daemon invoked at boot time to implement Multicast DNS and DNS Service Discovery. On 34Mac OS X 10.6 (Snow Leopard), 35.Nm 36is also the system-wide Unicast DNS Resolver. 37.Pp 38.Nm 39listens on UDP port 5353 for Multicast DNS Query packets. 40When it receives a query for which it knows an answer, 41.Nm 42issues the appropriate Multicast DNS Reply packet. 43.Pp 44.Nm 45also performs Unicast and Multicast DNS Queries on behalf of client processes, and 46maintains a cache of the replies. 47.Pp 48.Nm 49has no user-specifiable command-line argument, and users should not run 50.Nm 51manually. 52.Pp 53.Sh LOGGING 54There are several methods with which to examine 55.Nm Ns 's internal state for debugging and diagnostic purposes. The syslog(1) 56logging 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 63By 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 70Once this logging is enabled, users can additionally use syslog(1) 71to 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 79A SIGUSR1 signal will dump a snapshot summary of the internal state to 80.\" .Pa /var/log/system.log Ns : 81.Xr syslog 8 . 82.Pp 83.Dl % sudo killall -INFO mDNSResponder 84.Sh OPTIONAL ARGUMENTS 85.Nm 86accepts the following optional arguments: 87.Bl -tag -width "AlwaysAppendSearchDomains" 88.It Fl AlwaysAppendSearchDomains 89Append search domains for multi-labeled Partially Qualified Domain Name as well as single-labeled Partially Qualified Domain Name. 90This argument is not recommended because of the extra DNS traffic it generates and its adverse effect on battery life. 91.It Fl NoMulticastAdvertisements 92Prevent the system from advertising Bonjour services via Multicast DNS. 93.El 94.Pp 95To cause 96.Nm 97to run with these optional arguments when it launches on OS X 10.11 (El Capitan) and later, set the 98.Sy AlwaysAppendSearchDomains 99or 100.Sy NoMulticastAdvertisements 101boolean keys to true in /Library/Preferences/com.apple.mDNSResponder.plist and reboot. 102.Pp 103.Sh FILES 104.Pa /usr/sbin/mDNSResponder 105.Pa /Library/Preferences/com.apple.mDNSResponder.plist 106.Pp 107.Sh INFO 108.Pp 109For information on Multicast DNS, see 110.Pa http://www.multicastdns.org/ 111.Pp 112For information on DNS Service Discovery, see 113.Pa http://www.dns-sd.org/ 114.Pp 115For information on how to use the Multicast DNS and the 116DNS Service Discovery APIs on Mac OS X and other platforms, see 117.Pa http://developer.apple.com/bonjour/ 118.Pp 119For the source code to 120.Nm , see 121.Pa http://developer.apple.com/darwin/projects/bonjour/ 122.\" 123.Sh BUGS 124.Nm 125bugs are tracked in Apple Radar component "mDNSResponder". 126.\" 127.Sh HISTORY 128The 129.Nm 130daemon first appeared in Mac OS X 10.2 (Jaguar). 131.Pp 132Also available from the Darwin open source repository 133(though not officially supported by Apple) are 134.Nm 135daemons for other platforms, including Microsoft Windows, 136Linux, FreeBSD, NetBSD, Solaris, and other POSIX systems. 137