Error with check_uptime: NRPE: Unable to read output

[xerez]

This error appear when I try monitoring a Linux host with check_uptime:

In Nagios:
In my "linux.cfg" I have:

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define service{
        use                     generic-service
        host_name               name
        service_description     Uptime
        check_command           check_nrpe!check_uptime
        }

In my "commands.cfg" I added:

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# 'check_nrpe' command definition
define command{
        command_name    check_nrpe
        command_line    $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
        }

# 'check_uptime' command definition
define command{
        command_name    check_uptime
        command_line    $USER1$/check_uptime -H $HOSTADDRESS$
        }

In my "nrpe.cfg" I added:

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command[check_uptime]=/usr/local/nagios/libexec/check_uptime -w 5 -c 10

In the Linux host:
In my "nrpe.cfg" I added:

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command[check_uptime]=/usr/local/nagios/libexec/check_uptime -w 5 -c 10

In addition, when I execute this:

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./libexec/check_nrpe -H <host ip> -c check_uptime

The output is the same:

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NRPE: Unable to read output

But if I execute this:

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./libexec/check_nrpe -H localhost -c check_uptime

The output is:

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Uptime CRITICAL: 9 day(s) 1 hour(s) 37 minute(s) | uptime=13057.000000;5.000000;10.000000;

What's wrong or what's missing? Thanks.

[jdalrymple]

NRPE on your remote host is not communicating with check_nrpe on your localhost. Your 2nd test is irrelevant, very rarely is there a need to `check_nrpe -H localhost`

Verify that the firewall port 5666 is open on the remote host
Verify that nrpe is running on the remote host
Verify that the nagios server's IP is listed in allowed_hosts in the remote host's nrpe.cfg

[xerez]

All are correct. Also, others services like "check_load" work fine.

In the Linux client, I see in "/usr/lib/nagios/plugins/" that don't there "check_uptime", can be the problem?

Thanks.

[jdalrymple]

You will need that plugin there, so put it there and see if that solves your issue. Generally it's a different error seen when plugins are missing, but it's worth a shot.

You can get all the Nagios plugins here:

http://www.nagios.org/download/plugins

[xerez]

Nothing, appear the same error.

[jdalrymple]

Can the uptime command and see if you are even communicating with NRPE:

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[jdalrymple@localhost ~]$ /usr/local/nagios/libexec/check_nrpe -H <host ip>
I (0.4.3.131 2015-02-15) seem to be doing fine...

This was a windows host, but you should get some output similar just saying NRPE instead of the "0.4.3" business.

Also:

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[jdalrymple@localhost ~]$ nmap -p 5666 <host ip>
Starting Nmap 6.40 ( http://nmap.org ) at 2015-05-08 09:16 CDT
Nmap scan report for <host ip>
Host is up (0.0033s latency).
PORT     STATE SERVICE
5666/tcp open  nrpe

Nmap done: 1 IP address (1 host up) scanned in 1.25 seconds

If it doesn't say "open" under state - you have a service, network or firewall problem.

[xerez]

From Nagios server:

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nagios@localhost:~$ /usr/local/nagios/libexec/check_nrpe -H <host ip>
NRPE v2.13

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nagios@localhost:~$ nmap -p 5666 <host ip>

Starting Nmap 6.00 ( http://nmap.org ) at 2015-05-11 10:29 CEST
Nmap scan report for <host ip>
Host is up (0.0011s latency).
PORT     STATE SERVICE
5666/tcp open  nrpe

Nmap done: 1 IP address (1 host up) scanned in 0.38 seconds

[jdalrymple]

From Nagios server:

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nagios@localhost:~$ /usr/local/nagios/libexec/check_nrpe -H <host ip>
NRPE v2.13

This means your NRPE is working great and there is something haywire when it tries to execute the remote plugin.

Please post the relevent portion of your nrpe.cfg

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command[check_uptime]=<plugin path>check_uptime

and also

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ll <plugin path>

[xerez]

nrpe.cfg in Nagios:

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command[check_uptime]=/usr/local/nagios/libexec/check_uptime

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nagios@localhost:/usr/local/nagios/libexec$ ls -l check_uptime
-rwxr-xr-x 1 root nagios 129224 mar 28  2014 check_uptime

[jdalrymple]

Weird.

As I go back through the post I don't see where that we've tested check_uptime since you put it on the remote server. Can you su to nagios and then run check_uptime from there?

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[jdalrymple@localhost ~]$ sudo su nagios
[sudo] password for jdalrymple:
[nagios@localhost jdalrymple]$ cd /usr/local/nagios/libexec
[nagios@localhost libexec]$ ./check_uptime
Uptime OK: 50 day(s) 17 hour(s) 7 minute(s) | uptime=73027.000000;;;