NRPE Error – Unable to Read Output: Troubleshooting

nagiosnrpe

I have this problem with NRPE, all the stuff I've found so far on the net seems to point me at things I've already tried.

# /usr/local/nagios/plugins/check_nrpe -H nrpeclient

gives

NRPE v2.12

as expected.

Running the command by hand (as defined in nrpe.cfg on "nrpeclient", gives the expected response

nrpe.cfg:

command[check_openmanage]=/usr/lib/nagios/plugins/additional/check_openmanage -s -e   -b ctrl_driver=0 bat_charge

"Expected response"

But if I try to run the command from the Nagios server I get the following:

# /usr/local/nagios/plugins/check_nrpe -H comxps -c check_openmanage
NRPE: Unable to read output

Can anyone think of anywhere else I might have made a mistake with this? I've done the same thing on multiple other servers with no problem. The only difference I can think of with this is that this box is RHEL 5 based, whereas the others are RHEL 4 based.

Those two bits above that I've tested are the what most people seem to suggest when people have had this problem.

I should mention that I get a weird error in the logs when I restart nrpe:

nrpe[14534]: Unable to open config file '/usr/local/nagios/etc/nrpe.cfg' for reading 
nrpe[14534]: Continuing with errors...
nrpe[14535]: Starting up daemon
nrpe[14535]: Warning: Daemon is configured to accept command arguments from clients!
nrpe[14535]: Listening for connections on port 5666 
nrpe[14535]: Allowing connections from: bodbck,combck,nam-bck

Even though, it's plainly reading that /usr/local/nagios/etc/nrpe.cfg file to get the stuff it's talking about further down..

Best Answer

You have a rights problem.

Change the command to:

command[check_openmanage]=sudo /usr/lib/nagios/plugins/additional/check_openmanage -s -e -b ctrl_driver=0 bat_charge

(add sudo)

Then, add the nagios-user to the sudoers:

nagios ALL=(ALL) NOPASSWD:/usr/lib/nagios/plugins/additional/check_openmanage

Or you could just chmod the file... That also works.

If you are using CentOS, Red Hat, Scientific or Fedora, make sure to disable Defaults requiretty in the sudoers file.

Related Solutions

Linux – NRPE: Unable to read output

One good way to debug why the command being executed is not returning any valid output is to use strace. For example, I just had a problem running the check_linux_raid command via NRPE.

Run strace -f -p <nrpe pid>, and then execute the command manually from the system running nagios (e.g. /usr/lib64/nagios/plugins/check_nrpe -H remotename -c commandname -a arg1 arg2 ...).

Scan the output of strace for errors, such as permission denied or other similar errors that may occur. For example, in my case, selinux was denying permission to a file when running from the remote machine, even though that user has local access to that file.

Nagios NRPE: Unable to read output

Since I see there is no problem with the line you added to /etc/sudoers file:

nagios  ALL=(ALL) NOPASSWD: /usr/lib/nagios/plugins/

I suspect that there is a later entry in /etc/sudoers that override NOPASSWD option and that is reason for http-restart still asking for a password. With your above config, is nagios user a member of sudo group?

Just try to move this line to the end of /etc/sudoers file to exclude this possibility. Also make sure the nrpe user does not need a tty, by setting Defaults:nrpe !requiretty.

UPDATE Wed Jun 27 21:24:21 ICT 2012

To make the NRPE work, you also need to add sudo to your command definition in nrpe.cfg:

command[restart_http]=/usr/bin/sudo /usr/lib/nagios/plugins/http-restart

Best Answer

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Linux – NRPE: Unable to read output

Nagios NRPE: Unable to read output

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