DNS server address no longer stored in resolv.conf; where is it now?

I sometimes switch DNS servers, using the NetworkManager indicator in the taskbar; this worked fine with previous versions, and actually works fine with 12.04, too, except for one thing: I use Conky to display some system information, including the DNS address, and I noticed that it is now always displaying 127.0.0.1.

I looked in resolv.conf, which is where it gets this address, and sure enough, that's what it always says. I has a single line, with the admonishment not to edit the file by hand:

nameserver 127.0.0.1

The only way I know to check the DNS server address now is to open the network manager GUI to check the info page. So, where is this information stored now?

The information is managed internally by Network Manager. You can get this information on the command line using the included nmcli tool.

You can retrieve Network Manager's information for a particular network interface with the following command:

nmcli dev list iface eth0

(replace eth0 with the interface you are connecting with). The output will include information about the interface and the currently active connection on that interface:

GENERAL.DEVICE:                         eth0
GENERAL.TYPE:                           802-3-ethernet
...
IP4.DNS[1]:                             192.168.0.1
...

It shouldn't be too difficult to extract the information you are after from this output.

If you need a programmatic method of accessing this data that doesn't rely on the output of nmcli, this information should also be available from Network Manager's D-Bus interface.

Ubuntu developers should document these changes in /etc/resolv.conf, but have not.

Here is a list of quick commands to get you going.

1. Show the current DNS servers

   nm-tool | grep DNS
   

2. Define a static DNS server in /etc/dhcp/dhclient.conf. Add the following line, and restart local resolver:

   supersede domain-search "sub.mydomain.com", "domain.com";
   prepend domain-name-servers 192.168.0.1;
   

   From the command prompt:

   invoke-rc.d network-manager restart
   

Be aware that using nmcli may not always give you the full answer. e.g. if you use openconnect (or vpnc, presumably) to start a VPN, and if you have the resolvconf package installed (to take care of automatically managing /etc/resolv.conf), you'll find that it can still automatically insert the VPN's DNS settings into /etc/resolv.conf ahead of 127.0.0.1. In this circumstance, just checking (e.g.) "nmcli -f IP4 dev list" won't give you the true current DNS list. Not sure if this scenario affects you, but figured it worth mentioning.