feature request for some future distribution: It would be grand if resolv.conf modifications supported an "always-on" set of DNS options in case the stuff provided by the local LAN is fubar or doesn't have zones you want.
in /etc/sysconfig/network one would add something like ALWAYS_ON_DNS=a.b.c.d ALWAYS_SEARCH_DNS=myzone.tld
the DHCP client would then write its new resolv.conf, after which nameserver $ALWAYS_ON_DNS would be appended. If no search domain has been specified by the DHCP server, then search $ALWAYS_SEARCH_DNS will also be appended.
Is having resolv.conf not replaced when you make a DHCP connection what you want? Are you aware of the possibility of adding the line:
PEERDNS=no
to /etc/sysconfig/network ?
This is because it's really annoying to sign onto a new LAN and have X apps unable to find themselves because your search line has been overwritten by a braindead DHCP server.
The DHCP server has no ability to write anything to your machine. The DHCP client is doing it because you let it (the thing I said above will make it not).
