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dnsosx-elcapitanoscache

How to view DNS cache in OSX?

To list the entries of DNS cache in OSX 10.11.6, I tried dscacheutil -statistics but that didn't work.

$ sudo dscacheutil -statistics
Unable to get details from the cache node

How can I just print what is there in the DNS cache without flushing it?

Solution

  • mDNSResponder (multicast DNS daemon) SIGINFO signal can dump a snapshot summary of the internal state to /var/log/system.log, including the cache details. To do this:

    Keep system log opened in one terminal:

    tail -f /private/var/log/system.log

    Send a SIGINFO signal to mDNSResponder from another terminal:

    sudo killall -INFO mDNSResponder

    Then check the logs in first terminal, you would be able to see cache dump:

    mDNSResponder[98]: ------------ Cache -------------
mDNSResponder[98]: Slt Q     TTL if     U Type rdlen
mDNSResponder[98]:  52      1827 -U-      CNAME   17 www.sublimetext.com. CNAME sublimetext.com.
...
...
mDNSResponder[98]: Cache currently contains 154 entities; 3 referenced by active questions

    (For more info: man mDNSResponder)