I just upgraded a MacMini to Ventura 13.2.1 and DNS resolution failed. Browsers wouldn’t open and pinging a domain was failing. However, nslookup and dig continued to work fine…which was the clue as those tools don’t use mDNSResponder.
To cut a long story short (and I won’t bitch about how painful and useless was my call to Apple Support) I discovered that if I kill -9 the mDNSResponder process and its helper process, they immediately restart and DNS works properly. This is 100% reproducible (I shut down/restarted the Mac Mini four times)
I’ve seen numerous reports of this problem online - I don’t know what are the circumstances that make this happen as it clearly works for many users. In any case, here’s how to fix the problem.
In a terminal window, run the command ps aux | grep -i mdns and you’ll get a result like the following – the actual process id numbers will of course be different for each user
Then type the following, replacing those two numbers with the numbers displayed when you run the ps command above
sudo kill -9 284 275
You’ll be prompted for your password, type it in.
That fixes it…until the next time you start your Mac.
Obviously, I don’t know why this problem occurs but I speculate that the mDNSResponder process is starting before the computer has an active IP address available and the mDNSResponder is just hanging.
I’ve also had the same problem with the mDNSResponder since upgrading to Ventura (and yes, I’ve the current version of Ventura, and have even tried reinstalling)–it kicks in and takes over 97%+ of the CPU processes, causing excessive heat and then excessive fan usage. Killing the process is only temporary. Even the above ps and sudo kill -9 suggestion doesn’t stop it from coming back on again and again. I have to kill it every few minutes just to keep the fans from over-running. I thought of downgrading back to Monterey but that’s not an easy process. I’d even try an automator script if I could come up with one that would kill just this process when it shows up in activity monitor, but my scripting skills don’t seem up to the…task. BTW, this is a Intel i9 2019 16" MBP.
mDNSResponder definitely is killing the pleasure of using a Mac
An Apple-certified friend visiting this week offered to take a look at the problem. I was skeptical, particularly since a 2-hour session with a second-level Apple tech didn’t solved the problem last month.
However, my friend solved the problem, doing something I should have thought of but didn’t.
He just deleted the Ethernet and WiFi interfaces and then added them in again. Problem completely solved (tested by rebooting several times).
So the thought is that somehow the configuration files associated with those devices were somehow corrupted and the actions above created new configuration files.
