Change DNS Server From Terminal (or script) on Mac OS X

Question

How can I change my DNS server from the Terminal on Mac OS X? [I need this because my DNS is not working correctly with my VPN. Sometimes it's using the DNS for my main connection, and sometimes it's using the DNS specified for the VPN (which it should).]

Answer 1

You can use scutil interactively from the terminal. Run sudo scutil and run these commands, swapping your DNS servers in where appropriate:

> open
> d.init
> d.add ServerAddresses * 8.8.8.8 9.9.9.9
> set State:/Network/Service/PRIMARY_SERVICE_ID/DNS
> quit

Instead of using 8.8.8.8 and 9.9.9.9 use your DNS servers.

The only problem is this is not persistent across reboots. If you want permanent changes, you'll want ncutil. The reason editing /etc/resolv.conf isn't sufficient in newer versions of OS X is because configd now uses a database to store information of current settings, which other applications read. Certain applications will still read /etc/resolv.conf (host for example), although that is not the case for all applications.

Answer 2

You can use networksetup:

sudo networksetup -setdnsservers <networkservice> DNS1, DNS2, DNS3

eg (having the Airport connection use Google's DNS Servers)

sudo networksetup -setdnsservers AirPort 8.8.8.8, 8.8.4.4

You can find out the name of the network service by running networksetup -listallnetworkservices.

This is the same as if you were to edit the entires in the Network Preference Pane in System Preferences, so it is persistent across reboots.

You may be running into a DNS issue on Snow Leopard that occurs when the order DNS servers are queried changes (see question 84144))

Answer 3

You should be able to do it by editing /etc/resolv.conf (remember resolv.conf is reset after reboot), hope it helps - http://developer.apple.com/mac/library/documentation/Darwin/Reference/ManPages/man5/resolver.5.html