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).]
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 * 22.214.171.124 126.96.36.199 > set State:/Network/Service/PRIMARY_SERVICE_ID/DNS > quit
Instead of using
188.8.131.52 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.
You can use
sudo networksetup -setdnsservers <networkservice> DNS1, DNS2, DNS3
eg (having the Airport connection use Google's DNS Servers)
sudo networksetup -setdnsservers AirPort 184.108.40.206 220.127.116.11
You can find out the name of the network service by running
networksetup -listallnetworkservices. It'll be 'Wi-Fi' probably.
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))
I don't have enough points to reply to Chealion's post but to add on to it I'd start with listing the interfaces
Once you have the interface you'd like to change you can do the below (I'm using the Wi-Fi but you can do any other interface)
sudo networksetup -setdnsservers Wi-Fi empty sudo networksetup -setdnsservers Wi-Fi 18.104.22.168 22.214.171.124 sudo killall -HUP mDNSResponder
The first line of the above will empty out the DNS settings then follow it with the DNS servers we'd like to use and finely clear the DNS cache
To verify the DNS change you can do this before and after or simply after
scutil --dns | grep 'nameserver\[[0-9]*\]'
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