Sooo .. You are monitoring a fleet of AWS EC2 hosts via Nagios, and have yet to find an easy way to manage their host definitions .. Good news (if you happen to be using Ansible dynamic inventories) !! I created an Ansible template that loops thru all your EC2s and creates them for you ..
In addition, you can easily define Nagios service dependencies, helping you zero in on the root problem more quickly ..
Afraid of having too many AWS EC2 images and/or snapshots, thus running up your bill ?? Fear not !! I have you covered: