Comment 5 for bug 72341

I found this bug (and bug https://bugs.launchpad.net/ubuntu/+source/network-manager/+bug/98928?redirection_url=https%3A%2F%2Fbugs.launchpad.net%2Fubuntu%2F%2Bsource%2Fnetwork-manager%2F%2Bbug%2F98928) while researching a similar problem. It turned out that dhclient was modifying resolv.conf every time my ISP connection was established. I fixed this by modifying /etc/dhcp3/dhclient as follows (removing the domain and
host names from the "request" line):

=== modified file 'dhcp3/dhclient.conf'
--- a/dhcp3/dhclient.conf 2008-01-14 02:03:39 +0000
+++ b/dhcp3/dhclient.conf 2008-01-14 17:36:02 +0000
@@ -16,9 +16,8 @@
 #send dhcp-lease-time 3600;
 #supersede domain-name "fugue.com home.vix.com";
 #prepend domain-name-servers 127.0.0.1;
-request subnet-mask, broadcast-address, time-offset, routers,
- domain-name, host-name,
- netbios-name-servers, netbios-scope;
+request subnet-mask, broadcast-address, time-offset, routers;
+
 #require subnet-mask, domain-name-servers;
 timeout 30;
 #retry 60;

Before this change I could modify the domain name in network manager and see the changes in /etc/resolv.conf
along with a comment saying that the file was modified by network manager (DO NOT EDIT!!!!). However when networking was started or restarted (i.e. /etc/init.d/networking restart or system boot) then resolv.conf would be overwritten,(including the comment line). After the change shown above resolv.conf is not modified.

Hope this helps