[Nagiosplug-help] NRPE: Unable to read output

Brian Tomjack btomjack at suretytek.com
Fri Feb 20 16:54:45 CET 2009

Yesterday during my troubleshooting i thought maybe that would be a 
helpful item to try as well. i killed nrpe via xinetd and just ran it 
manually with no ssl and then tried that. with no avail. i also ran a 
traffic dump at the same time through the core router that they have in 
common and it looks like the request is being sent out just fine. the 
remote nrpe is sending back the unable to read output to nagios so it is 
not the check_nrpe plugin on the nagios server that is having the problem.

So i decided to downgrade the plugins and nrpe to a version that i had 
been using successfully on other servers thinking maybe it was just an 
incompatibility. So i downgraded recompiled and reconfigured, just in 
case. Unfortunately this did not yield a changed result either.

This server will only be a mail server for about 6-9 months more so, i 
may just live with not knowing.


Andreas Wehrmann wrote:
> hmm strange, does it work without encryption?
> Andreas
> Brian Tomjack wrote:
>> Unfortunately i think that nrpe thinks its just fine as well. the only 
>> thing in the logs (with debugging set to 1 in the nrpe.cfg) are lines 
>> of the following every 10 minutes when nagios checks the load and the 
>> mailq
>> Feb 19 11:39:38 ns1 xinetd[27766]: START: nrpe pid=9248 
>> from=nagios.server.ip.address
>> Feb 19 11:39:38 ns1 nrpe[9248]: INFO: SSL/TLS initialized. All network 
>> traffic will be encrypted.
>> Feb 19 11:39:39 ns1 xinetd[27766]: EXIT: nrpe status=0 pid=9248 
>> duration=1(sec)
>> Feb 19 11:39:42 ns1 xinetd[27766]: START: nrpe pid=9256 
>> from=nagios.server.ip.address
>> Feb 19 11:39:42 ns1 nrpe[9256]: INFO: SSL/TLS initialized. All network 
>> traffic will be encrypted.
>> Feb 19 11:39:42 ns1 xinetd[27766]: EXIT: nrpe status=0 pid=9256 
>> duration=0(sec)
>> good thought though,
>> Brian
>> Andreas Wehrmann wrote:
>>> Stupid questions, but have you looked into the log messages?
>>> I had some similiar problem and the log told me that the machine that's
>>> trying to get information via nrpe is not allowed.
>>> Hopefully it's just as easy as that.
>>> Regards,
>>> Andreas
>>> Brian Tomjack wrote:
>>>> Well i think this is the right place for this, since it seems plugin 
>>>> related to me.
>>>> Here is the setup, my nagios server is on the same network, behind 
>>>> the core router. The server i am trying to monitor is behind an 
>>>> outlying firewall. I have configured both to work over port 5666 and 
>>>> have opened the appropriate firewall port to the remote host.
>>>> I know that nagios i working fine because it has several hundred 
>>>> other hosts on it all working fine. and i know that nrpe must be 
>>>> (mostly) working ok on the remote host in question because the 
>>>> check_load via nrpe is working fine to that remote host.
>>>> My problem is that when the nagios server checks the mailq on the 
>>>> remote host it gets back:
>>>> [root at ns1 ~]# /usr/local/nagios/libexec/check_nrpe -H 
>>>> remote.server.ip.address -c check_mailq
>>>> NRPE: Unable to read output
>>>> on the remote host, in the nrpe config:
>>>> command[check_mailq]="sudo /usr/local/nagios/libexec/check_mailq -w 
>>>> 120 -c 175"
>>>> from the remote host /etc/sudousers:
>>>> nagios ALL=NOPASSWD: /usr/local/nagios/libexec/check_mailq
>>>> now, on the remote host, i can run it manually and get:
>>>> [nagios at ns1 ~]$ sudo /usr/local/nagios/libexec/check_mailq -w 120 -c 
>>>> 175
>>>> CRITICAL: mailq is 194 (threshold c = 175)|unsent=194;120;175;0
>>>> and finally, on the remote host. if i configure it to allow requests 
>>>> from and run the nrpe command i get this:
>>>> [nagios at ns1 ~]$ /usr/local/nagios/libexec/check_nrpe -H -c 
>>>> check_mailq
>>>> NRPE: Unable to read output
>>>> (the same result as when run from the nagios server)
>>>> so im stumped. the plugin is working on the remote host, and nrpe is 
>>>> working because i can execute the check_load via nrpe from the 
>>>> nagios server to the remote host and it works just fine. its only 
>>>> when i run the check_mailq via nrpe do i get a output read error. 
>>>> the nagios server is a fedora server, the remote host is a centos 
>>>> server. im not sure what else to check on so any suggestions are 
>>>> appreciated, as this is the only machine that i am having problems 
>>>> monitoring the mailq on.
>>>> Brian
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