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How to Clear DNS Cache with discoveryutil in Mac OS X Yosemite

by 5 Comments

A lot of OS X Yosemite users are complaining that dscacheutil is not helping with clearing DNS cache. Here is quick guide to try with discoveryutil.

To completely clear all DNS caches in OS X Yosemite, target both MDNS (Multicast DNS) and UDNS (Unicast DNS) with two different commands.

Step 1.  Open Terminal.app

Step 2. Insert this command to terminal to

Clear MDNS Cache

sudo discoveryutil mdnsflushcache

Hit return and enter the admin password when requested.

Clear MDNS Cache-2

Step 3. Insert this command to terminal to

Clear UDNS Cache

sudo discoveryutil udnsflushcaches

Hit return and enter the admin password when requested.

Note that caches is plural with the latter command, a subtle but important syntax difference.

Clear UDNS Cache-2

You can also string the above two commands together if you want, the following will even verbally announce when the caches have been cleared.

sudo discoveryutil mdnsflushcache;sudo discoveryutil udnsflushcaches;say flushed

Clear MDNS UDNS Cache-2

Indeed MDNS and UDNS caches are different, but I’ve found that for functional DNS cache to actually clear in OS X Yosemite both commands are necessary. It’s entirely possible that you only need to clear one or the other for your own needs.

 

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Comments

  2. Shinmaikeru says

    With Yosemite 10.5.5, editing the hosts file has no effect, and the command you give above returns just “sudo: discoveryutil: command not found”.

    You can’t do web dev if you cannot use the hosts file as a local DNS override. Do you have a solution?

    Reply

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