Goodbye, discoveryd. Hello again, mDNSResponder.

Posted on in System Administration

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Once again, Apple has made a change in how DNS is handled in Mac OS X. Originally, Yosemite (10.10) had replaced mDNSResponder with discoveryd. This meant that all of those who had made a change to force mDNSResponder to always append search domains to DNS lookups had to make a new change to accommodate discoveryd.

Lo and behold, with 10.10.4, discoveryd is out and mDNSResponder is in. Below is the new process you'll need to follow to get your DNS lookups working as expected.

  1. Before you do anything, make sure you have updated to at least OS X 10.10.4.
  2. You will need to edit /System/Library/LaunchDaemons/ Add <string>-AlwaysAppendSearchDomains</string> to the list of strings in the ProgramArguments \<array>. Please note that the argument only has a single leading dash.
  3. Restart mDNSResponder to see your changes take effect.

    sudo launchctl unload -w /System/Library/LaunchDaemons/
    sudo launchctl load -w /System/Library/LaunchDaemons/
  4. Profit!

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