Q: Is it possible to retrieve information regarding the current internal state of mDNSResponder?A: Yes. Starting in Mac OS X 10.3, you can send a SIGINFO signal to the mDNSResponder daemon which will cause it to output its current internal state to the system log (/var/log/system.log). This allows you to retrieve information about mDNSResponder's cached DNS resource records, and it allows you to see the active DNS Service Discovery (DNS-SD) operations. You can send the SIGINFO signal from the Terminal by typing: $ sudo killall -info mDNSResponder
Listing 1: Example system.log containing mDNSResponder state info. mDNSResponder-58.4 (Jan 28 2004 16:31:36) ---- BEGIN STATE LOG ----
Active: PTR en1 26 _ftp._tcp.local. PTR Ice Cube._ftp._tcp.local.
Inactive: SRV en1 22 Ice Cube._ftp._tcp.local. SRV Ice-Cube.local.
Inactive: TXT en1 1 Ice Cube._ftp._tcp.local. TXT
Inactive: PTR en1 26 _ssh._tcp.local. PTR Ice Cube._ssh._tcp.local.
Inactive: Addr en1 4 Ice-Cube.local. Addr 10.0.1.2
Cache currently contains 5 records; 1 referenced by active questions
11251: ServiceBrowse _http._tcp.local.
10755: ServiceBrowse _ftp._tcp.local.
10499: ServiceBrowse _webdav._tcp.local.
10243: ServiceBrowse _nfs._tcp.local.
9731: ServiceBrowse _afpovertcp._tcp.local.
8195: ServiceRegistration Ice Cube._ssh._tcp.local.
7939: ServiceRegistration Ice Cube._ftp._tcp.local.
mDNSResponder-58.4 (Jan 28 2004 16:31:36) ---- END STATE LOG ----
Note: On Linux, Solaris, and FreeBSD, you send mDNSResponder (known as mdnsd on those systems) a SIGUSR1 signal instead of a SIGINFO signal. Document Revision History| Date | Notes |
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| 2006-10-03 | Updated SIGUSR1 comment for Linux, BSD, and Solaris. | | 2004-02-06 | Explains how to obtain information regarding the internal state of mDNSResponder. |
Posted: 2006-10-03
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