[Wolves] Icinga (Nagios)

chris procter chris-procter at talk21.com
Fri May 14 23:27:41 UTC 2010

> I've setup up CentOS 5.4 --> Icinga on one of the boxes Adam Sweet gave 
> me here at work. I stuck CentOS on as I really wanted RHEL 5 (Possibly 6) 
> but have no money :-(

If you really want to try the rhel6 beta you can get it from http://www.redhat.com/rhel/beta/ and follow the links, but Centos is simply RHEL without the trademarks so unless you want a support plan your not going to gain anything. 

> Icinga is a fork of Nagios the network monitoring system allowing you to 
> monitor internal and external equipment. http://www.icinga.org/

We use nagios partially because I inherited it and partisally because its easy to customise with a bit of shell scripting to monitor anything you can think of.

> Anyway [Ron] I take it to monitor a remote machine I will need the 
> remote sites firewall to let me in? Does my firewall need to let them 
> in? If the answer is yes to my firewall I'm stuffed. :-(

There are a number of ways of doing remote monitoring with nagios, the simplest is using ssh, gtheres a pluging called check_by_ssh (or something) that runs on the master a logs into the remote machine via ssh, runs the check plugin and returns the results to the master. You obviously need to be able to get an ssh connection to the remote host and login using certificates rather then passwords, but the master initiates the connection, the remote host just listens.

Theres nrpe, which is a deamon that runs on the remote host, listening on a port for connections from the master. The master runs the check_nrpe plugin that sends a message to the nrpe deamon on the remote host asking it to run a check, nrpe runs the check and passes back the results which check_nrpe returns to the main nagios deamon. Obviously you need to be able to connect to the nrpe port on the remote host, but agaion this is initiated by the master.

Theres also a number of plugins that check network services, so say your trying to check if your website is up and working the best way to do it is to have a plugin ruuning on the master that actually pulls down http://dickturpin.con and checks if the page it gets matches what it expects, if so it passes and if it gets something different then theres a problem.  (Theres similar things for databases and pop/imap/smtp servers, I can't remember names but have a look at http://www.monitoringexchange.org/ ).   This doesn't require any access to the remote machine and if you can browse to the site through your firewall you can monitor it

Not sure any of that helps any,

chris :)


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