Nagios/NRPE relationship

[Martyn]

Marc it makes perfect sense now, thanks for the detailed explanation.

Thanks again!

Martyn

-----Original Message-----
From: Marc Powell [mailto:marc at ena.com] 
Sent: 05 March 2009 16:29
To: Nagios Users
Subject: Re: [Nagios-users] Nagios/NRPE relationship


On Mar 4, 2009, at 5:26 PM, Martyn wrote:

> Hi all, hope you do no think this is a stupid question; however I have 
> to ask it anyway for a better understanding
>

> Command[check_smtp]=/usr/local/nagios/libexec/check_smtp -H localhost
>
> Do they have to use the -H localhost directive or is there something  
> different they can use, the localhost just does not seem right  
> looking at the other examples above.
>

Yes, check_smtp connects to a 'remote' smtp server and verifies that  
it answers so it needs to know what IP to connect to. It doesn't need  
NRPE to do that. If this remote server answers on port 25 on an IP  
reachable from your nagios host, you could just as easily run it from  
your nagios host and probably have more reliable results. The only  
scenario where the check above makes sense is if the SMTP server only  
accepts connections from the local machine.

You can always run 'check_<plugin> --help' to see what parameters are  
required and available.

NRPE is only needed for checking things that don't expose external  
services. Things like disk space, cpu utilization, memory use, etc..  
Any network aware daemons like sendmail, postfix, apache, sshd, etc  
can generally be checked without using NRPE.
> Then on my Nagios Server, under the .cfg box I want to monitor I  
> define the command:
>
> define service{
>         use                              generic-service
>         host_name                   linux-server
>         service_description       SSH
>         check_command          check_nrpe!check_ssh
>         }
>

This is another one that doesn't really make sense to run through  
NRPE. check_ssh tries to connect to port 22 on a specified host (-H)  
to see if sshd is listening. You'd want to perform that test from a  
different box than sshd is running on to make sure it's listening  
publicly. Running directly from nagios is better.

define service{
         use                              generic-service
         host_name                   linux-server
         service_description       SSH
         check_command          check_ssh
         }

Assuming your check_ssh command definition looks something like --

define command {
     command_name                   check_ssh
     command_line                   $USER1$/check_ssh -t 30 -H  
$HOSTADDRESS$
     }

--
Marc


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------------------------------------------------------------------------------
Open Source Business Conference (OSBC), March 24-25, 2009, San Francisco, CA
-OSBC tackles the biggest issue in open source: Open Sourcing the Enterprise
-Strategies to boost innovation and cut costs with open source participation
-Receive a $600 discount off the registration fee with the source code: SFAD
http://p.sf.net/sfu/XcvMzF8H
_______________________________________________
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::: Please include Nagios version, plugin version (-v) and OS when reporting any issue. 
::: Messages without supporting info will risk being sent to /dev/null