MDNSD(8) | System Manager's Manual | MDNSD(8)

# NAME

`mdnsd` —
Multicast and Unicast DNS daemon

# SYNOPSIS

`mdnsd` |

# DESCRIPTION

`mdnsd` (also known as `mDNSResponder` 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), `mdnsd` is also the system-wide Unicast DNS Resolver.

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

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

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

## LOGGING

There are several methods with which to examine `mdnsd`'s internal state for debugging and diagnostic purposes. The syslogd(8) 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:

`# pkill -USR1 mdnsd`

A SIGUSR2 signal toggles packet logging:

`# pkill -USR2 mdnsd`

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

`# pkill -INFO mdnsd`

# FILES

/usr/sbin/mdnsd

# SEE ALSO

dns-sd(1), pkill(1), syslogd(8)

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 Discovery APIs on Mac OS X and other platforms, see http://developer.apple.com/bonjour/

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

# HISTORY

The `mdnsd` daemon first appeared in Mac OS X 10.2 (Jaguar).

Also available from the Darwin open source repository (though not officially supported by Apple) are `mdnsd` daemons for other platforms, including Mac OS 9, Microsoft Windows, Linux, FreeBSD, NetBSD, Solaris, and other POSIX systems.

# BUGS

`mdnsd` bugs are tracked in Apple Radar component "mDNSResponder".

February 27, 2011 | NetBSD 9.4