I get tired of trying to figure out all the various ways /etc/resolve.conf can get modified, for all my static hosts,
if it's a link, I replace it with the file with the contents I want, then run:
chattr +i /etc/resolve/conf
That prevents any further messing with the file. It does mean you are on the hook for any needed updates.
The alternative is figuring out who (which process(es)) is maintaining the file and get the configs to those files
straightened out. I manage my own DNS and DHCP servers so I know what resolve.conf needs to have, but the
various OS's drive me nuts, so I remove their ability to screw things up.
Chris