Nagios Core - threshold settings?

[supermop2000]

Hi all,

First off, I would like to say that I am very new to Nagios - I didnt even know it existed and I've been a systems engineer for around 12 years.

I have recently moved to a company which use Nagios Core as their main monitoring platform for servers and network devices. It's a fairly basic setup, but I'm REALLY struggling to understand how Nagios works at all. It's very fiddly and relies entirely on the Linux file system. I've lost count how many times I've broken the whole system just by mis-aligning some of the config files or the odd typo.

Anyway I didnt come here to rant.

I have been trying to figure out, for the past 6 months, how to change the Nagios reporting thresholds - for example, our disk thresholds that our previous sysadmin setup are now no longer relevant due to expanding disk sizes. We need to tweak the warn and critical threshold, but I cannot figure out where I set this. The online documentation is sporadic and somewhat ambiguous.

Can anyone point me in the right direction here?

The most progress I've made so far, is finding the NRPE.CFG file on the Nagios host, but the thresholds in there are all defined as $ARG1, $ARG2 etc and I have no idea where these $ARG variable values are defined. I've spent months searching and found nothing to help.

Cheers
Greg

[gormank]

I think the first thing you need to do is locate your nagios config files. Assuming you use Nagios Core, the .cfg files will have info on hosts, services, hostgroups, etc. A service in nagios-speak is a check of something such as disk usage, memory, etc. You should see in the web interface if you use Nagios core or XI. It makes a big difference you you need to know. XI store config info in a DB so you shouldn't manually edit nagios .cfg files in XI.
The nrpe.cfg file you found is the config for nrpe which is a service running in monitored hosts that listens for requests from the nagios server to do checks. Nrpe isn't the only way to run checks, and it may not be in use on your system.
Nagios is almost infinitely configurable so no one can say how your system checks things without more info.

You can use
ps -ef | grep nagios
to see processes, or
locate nagios | grep cfg$
to look for related config files. It's crude, but quick...

Arguments for checks could be in the services .cfg files, or in templates.

Once you find out which nagios you use and your .cfg files you can start by concentrating on how disk usage is checked to get a feel for things.

[gormank]

Sorry, the subject said core. Forget anything I said about XI...

[snapier3]

New to core, gonna be diving deep, you should probably own this;

Nagios Core Administration Cookbook Second Edition
ISBN-13: 978-1785889332
ISBN-10: 1785889338

“Never memorize something that you can look up.”
~Alert Einstein