When working with more complex setups for testing and developing one often needs a way to assign multiple domain names to locally running services. This allows to use name based virtual hosting, be it with a simple Nginx based proxy or a locally running Kubernetes cluster. MacOS allows to redirect the DNS queries to different nameservers based on the queried domain.
DNS configuration in MacOS
Disclaimer: I did not follow up to the authoritative documentation about this. So please take this with a certain level caution.
It seems the way to go to configure DNS servers in MacOS is currently by using the CLI tool scutil. It seems that the information in /etc/resolv.con reflects the configured primary DNS server and is updated automatically by the system whenever this changes. There is also configuration in /etc/resolver/... which seems to be a deprecated way of configuring the DNS system.
How to do it
The man pages for the tools and the help command in the interactive shell of scutil are a good companion, they explain everything in detail.
Here is one example:
sudo scutil # Overview of commands help # List of DNS related configuration entries list .*DNS # Preparing a dataset d.init d.add ServerAddresses * 127.0.0.1 d.add SupplementalMatchDomains * test # It seems to be possible to set the port number # d.add ServerPort # 1234 set State:/Network/Service/local-dns-test-domain/DNS quit
How to verify
Dump packages via tcpdump is the best way to observe this:
sudo tcpdump -n -i lo0 port 53
If you run ping something.test then you would see the following output:
IP 127.0.0.1.55741 > 127.0.0.1.53: 584+ A? something.test. (32)
It may be required to flush a few DNS related caches:
sudo dscacheutil -flushcache sudo killall -HUP mDNSResponder
- The most relevant source of information have been the answers and the comments regarding the following question on Stackexchange: https://apple.stackexchange.com/questions/74639/do-etc-resolver-files-work-in-mountain-lion-for-dns-resolution/385218