System Monitoring with OpenBSD - PhxBUG

Nagios - Active vs. Passive Checks

Active = the box running the nagios daemon does the check
Passive = the client runs the check and reports to the server

This requires some additional software

NRPE
Active checks
Used to run commands on remote machines
daemon runs on client, listens for requests from the server
NSCA
Passive checks
Requires an additional daemon on your nagios server

These require more setup. They can be complex, so I won't really get into them too much, other than show you their results.

We use NRPE to check disk usage.

NSCA ... it's kind of a different beast. Personally, I think it's best for things that don't change that often. OpenBSD users? Think NSCA + sensorsd(8) for when your CPU temperature hits 95 degrees