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alexus
Asked: 2014-05-17 12:37:37 +0800 CST

nagios nrpe unable to read output

  • 772

I'm trying to use check_nrpe to check on a remote server, but it's not working and I can't figure out what am I missing...

# /usr/lib/nagios/plugins/check_nrpe -H XXX -c check_load -a 6,5,4 8,7,6
NRPE: Unable to read output
#

remote's server syslog message:

nrpe[18058]: Connection from XX.XX.XX.XX port 16267
nrpe[18058]: Host address is in allowed_hosts
nrpe[18058]: Handling the connection...
nrpe[18058]: Host is asking for command 'check_load' to be run...
nrpe[18058]: Running command: /usr/bin/sudo /usr/lib64/nagios/plugins/check_load -w 6,5,4 -c 8,7,6
nrpe[18058]: Command completed with return code 1 and output: 
nrpe[18058]: Return Code: 1, Output: NRPE: Unable to read output
nrpe[18058]: Connection from XX.XX.XX.XX closed.

to verify it manually, I issue same command on a remote shell:

bash-4.1$ id
uid=497(nrpe) gid=497(nrpe) groups=497(nrpe) context=unconfined_u:unconfined_r:unconfined_t:s0-s0:c0.c1023
bash-4.1$ /usr/bin/sudo /usr/lib64/nagios/plugins/check_load -w 6,5,4 -c 8,7,6
OK - load average: 0.21, 0.23, 0.19|load1=0.210;6.000;8.000;0; load5=0.230;5.000;7.000;0; load15=0.190;4.000;6.000;0; 
bash-4.1$
sudo

3 Answers

  1. Best Answer

    ... the issue was even though nrpe_user inside of /etc/nagios/nrpe.cfg was set to nrpe, for whatever reason nrpe was running as nagios user instead, so I had to readjust sudoers.d file and it's start working right away ...

    # grep nrpe_user /etc/nagios/nrpe.cfg
nrpe_user=nrpe
# ps auxwww | grep nrpe
nagios   25388  0.0  0.0  41332  1240 ?        Ss   11:32   0:00 /usr/sbin/nrpe -c /etc/nagios/nrpe.cfg -d
root     26230  0.0  0.0 103252   828 pts/3    S+   11:47   0:00 grep nrpe
# cat /etc/sudoers.d/01_nagios 
Defaults:nagios !requiretty
nagios      ALL=(ALL)   NOPASSWD:   /usr/lib64/nagios/plugins/
#
    • 6

  2. This can be caused by sudo's "requiretty" setting. The real question, though, is why you're running check_load through sudo anyway.

    So, to fix this: either disable requiretty (just for the nagios/nrpe user) or stop running the plugin through sudo.

    • 1

  3. On the machine being checked, locate the nrpe.cfg file and inside that, the entry for "check_load". It will look something like this:

    command[check_load]=/usr/lib64/nagios/plugins/check_load -w 15,10,5 -c 30,25,20

    Try running the command on that machine - everything to the right of the equals sign above and see what you get.

    /usr/lib64/nagios/plugins/check_load -w 15,10,5 -c 30,25,20

    I'll bet its looking for check_load in /usr/lib/nagios/plugins instead of /usr/lib64 or something like that.

    • -1