mDNSResponder does not start since Security Update 2020-004 High Sierra

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mDNSResponder does not start since Security Update 2020-004 High Sierra

Hello,

since installing Security Update 2020-004 High Sierra on my Macbook Pro 13" early 2011 mDNSResponder does not start anymore.

The process is simply not there:


ps aux | grep -i mdnsresponder
root              1847   0.0  0.0  4331636   5228   ??  Ss   26Jul20   0:25.01 /usr/sbin/mDNSResponderHelper

Hence, DNS resolution does not work.

I tried rebooting, disabling SIP, and loading and unloading mDNSResponder, to no avail.

I also tried enabling launchctl logging as well as capturing the startup of mDNSResponder with dtruss.

I can see that mDNSResponder shuts down, but I could not find any indication of why.

Any pointers or ideas on what might cause this issue or how to debug and/or fix it?

MacBook Pro 13″, macOS 10.13

Posted on Aug 19, 2020 9:25 PM

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Answer 1

Best reply

BDAqua

Level 10

240,215 points

Aug 20, 2020 8:09 AM in response to oggy123

Are you running any VPN, Anti-Virus, or Cleaning apps?

Safe Boot, (holding Shift key down at startup), does the problem occur in Safe Mode?

Safe mode attempts to repair Disks & clears lots of caches & loads safe Drivers, & prevents loading of 3rd party extensions, so if Safe Mode works try again in regular boot.

To find out if it's system wide or user specific, try this...

Open System Preferences>Users & Groups, unlock the lock, click on the little plus icon, make a new admin account, log out & into the new account.

Does it work in the new account?

Reinstall the OS.

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Answer 2

oggy123 Author

Level 1

8 points

Aug 21, 2020 3:55 PM in response to BDAqua

Thank you for the reply!

I do not run any VPN, Anti-Virus or Cleaning Apps. I tried safe mode as well as creating a new admin user, both did not make mDNSResponder to work.

I am really not keen on reinstalling the OS though..

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Answer 3

oggy123 Author

Level 1

8 points

Aug 31, 2020 8:34 PM in response to BDAqua

Since nothing else worked, I re-installed MacOS over the existing installation. That did not help. Finally, wiping the disk and installing MacOS from scratch did the trick. Maybe it was a bad sector on the SSD.

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Answer 4

BDAqua

Level 10

240,215 points

Aug 21, 2020 4:01 PM in response to oggy123

I know, but sadly a reinstall is needed far too often anymore, it just reinstalls the OS, it shouldn't require any of your files to need redoing, though you always want a good backup.

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Answer 5

BDAqua

Level 10

240,215 points

Aug 31, 2020 8:38 PM in response to oggy123

Good work, great news, thanks for the report, take care my friend.

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mDNSResponder does not start since Security Update 2020-004 High Sierra

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