Using dhclient to automatically change IP addresses of Raspberry Pi on start-up

So, in my previous post I dealt with changing IP addresses on my Pi cluster by scp'ing the new IP addresses after the Pi had started up and established a network, and creating an ssh/config file from that info.

This is fine for most occasions. But I have one instance set-up to run zookeeper. I'd have to go around and change the config files on all my other Pi's. Ansible could cure this, and I'll get there one of these days. But I'm not there today. And actually - I think I'll use the script I wrote previously to update ansibles' hosts file. I just now thought of that.

Anyway - I want the zookeeper Pi to always have the same address.