I have an internet-facing linux system which uses DHCP for its internet interface. The DHCP client re-writes my /etc/resolv.conf, which prevents me from using the nameserver installed on it. I don't want to use the DHCP-provided nameservers, I want to use the local one.
Make your change to /etc/resolv.conf, then mark it as immutable:
# chattr +i /etc/resolv.conf
# lsattr /etc/resolv.conf
Kind of a hack, but it works.
RedHat users might enjoy Stop DHCP from changing resolv.conf