I have been playing around a bit with running Nagios on the Raspberry Pi for a while now and it works pretty well.
Even though I did the simplest kind of install of Nagios 3 with apt-get there was a couple of things that needed poking at to get external commands running.
Firs make sure that your webserver user is a member of the nagios group, and secondly change the group permissions lite below.
construct:/usr/lib/nagios/plugins# chmod g+w /var/lib/nagios3/rw
The above should be pretty self explanatory. I have no memory of actually adding the www-data user to the nagios group, but make sure that is done or the external commands wont work.
I’m currently monitoring 16 hosts – with a total of just about 30 checks which has to be seen as very little – and so far there has been no issues due to the Pies limitations.
Though it’s mostly just to test it still gives me some situational awareness which is always nice.