Nagios Support Forum

Hi

I am new to Nagios, and I am getting there slowly.

I just discovered last night... check_all_disks reports only "Disk OK". I wanted to see free space so added a plugin to get the free space. Turns out check_all_disks (which uses check_disk) just checks the local disk as all my servers reported the same size! More research, found out I needed check_nrpe!check_all_disks. So now I got that working. BUT...

What about all other checks? This got me worried, are other check_xxx only reporting local server? check_cpu for example is showing a different value for each server, BUT its reporting a different value to another monitoring system I have, which is alerting me to high cpu (and nagios is not). So got me thinking, is check_cpu only checking the local server?

So do I use check_nrpe!check_xxx on all my services? Obviously we want to check remote servers, yet documentation does not detail check_nrpe!check_xx much, I eventually found it on someone else's blog.

Thanks a lot

NRPE is the Nagios Remote Plugin Executor and is not used for local checks. Some checks, such as check_cpu and check_disk, will only work on localhost. This is because you cannot check a remote machine's CPU usage without having an agent/daemon running on that machine. NRPE is that daemon.

Other checks like check_http have the -H parameter and are used typically against remote hosts. NRPE is used to run checks which would normally only work on localhost *on* the remote machines.

Does that make sense?

Yes it makes sense thanks. But is there somewhere that clearly lists when I need to use check_nrpe? For example, check_imap, check_pop. These could either be checking them via a port on a remove server (so no check_nrpe) or checking some internal process (so check_nrpe). Is there somewhere we can confirm this?

Well, think of it this way, plugins are completely standalone in many cases, however, as NRPE remotely executes them as if you were doing it by hand, and then returns that data to Nagios, you can use it with any plugin. There are no plugins that I know of that are designed specifically for NRPE. Though as you noted, many do not have the ability to remotely query a system for the data they are looking for, as it deals with the hardware or software layer directly. That is the ideal use case for NRPE or a agent like it.