Ross S. W. Walker wrote:
Nagios can start very simple, but has the ability to end up very complex.
It's configs take a modular approach, you have monitors, monitors belong in groups, groups have operators/administrators, etc.
We just finished setting up Nagios at our office. It's not that bad once you break things out to sensible filenames instead of using one big config file. We stripped it down to just the essentials and are slowly building out our configuration to monitor additional services and hosts.
The other trick that we use is FSVS, which means that we have very good records as to what configuration file changes we made on the server. (FSVS is a front-end for storing stuff like /etc in a SVN repository.) It's extremely useful to be able to log configuration changes, browse past changes, do diffs on the files, etc.