I recently went back to a Mac laptop and encountered an interesting issue. I needed to make some changes to /etc/resolv.conf to reflect a modified search path and since /etc/resolv.conf is a symlink to /private/etc/resolv.conf I edited the latter file. All was well until I connected to a different network. Now my /private/etc/resolv.conf file, which clearly states that it's an auto-generated file, wasn't updated resulting in the "host" command (among other things) breaking. After posting on Apple's forums I ended up answering my own question.
/private/etc/resolv.conf is itself a symlink to /var/run/resolv.conf which is the file that is auto-generated. I ended up discovering that after looking at the /private/etc/resolv.conf file in my oldest Time Machine backup. That'll learn me.