Nagios Support Forum • check_nrpe -c check_procs Not Working

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check_nrpe -c check_procs Not Working

Posted: Mon Aug 17, 2020 1:46 pm

by wrobj0

I've read through at least ten different threads, and I cannot get this to work.

In the UI, the check is configured as such:

$USER1$/check_nrpe -2 -H $HOSTADDRESS$ -t 30 -c $ARG1$
ARG1 = check_procs -a '-c 1:1024 -Csshd'

This was working for a couple of years; I have no idea when it stopped working, but I discovered it today when trying to add a check for ns-slapd. It doesn't matter what process I choose, sshd, httpd, ntpd, etc., they all fail.

When I run the command from the UI, it returns nothing (just the full command, no error or anything). When I run it from the CLI, I get this:

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# /usr/local/nagios/libexec/check_nrpe -H <TARGET HOST> -t 30 -c check_procs -a "'-C sshd' '-c 1:'"
Usage:
check_procs -w <range> -c <range> [-m metric] [-s state] [-p ppid]
 [-u user] [-r rss] [-z vsz] [-P %cpu] [-a argument-array]
 [-C command] [-k] [-t timeout] [-v]

These are all the combinations I tried:

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# /usr/local/nagios/libexec/check_nrpe -H <TARGET_HOST> -c check_procs -a "'sshd' '1:'"
CHECK_NRPE: Receive header underflow - only 0 bytes received (4 expected).

# /usr/local/nagios/libexec/check_nrpe -H <TARGET_HOST> -c check_procs -a '"sshd" "1:"'
CHECK_NRPE: Receive header underflow - only 0 bytes received (4 expected).

# /usr/local/nagios/libexec/check_nrpe -H <TARGET_HOST> -c check_procs -a '"-C sshd" "-c 1:"'
CHECK_NRPE: Receive header underflow - only 0 bytes received (4 expected).

# /usr/local/nagios/libexec/check_nrpe -H <TARGET_HOST> -c check_procs -a '"-C sshd" "-c 1:'
CHECK_NRPE: Receive header underflow - only 0 bytes received (4 expected).

# /usr/local/nagios/libexec/check_nrpe -H <TARGET_HOST> -c check_procs -a "'-C sshd' '-c 1:'"
CHECK_NRPE: Receive header underflow - only 0 bytes received (4 expected).


# /usr/local/nagios/libexec/check_nrpe -H <TARGET_HOST> -c check_procs -a ''-C sshd' '-c 1:''
Usage:
check_procs -w <range> -c <range> [-m metric] [-s state] [-p ppid]
 [-u user] [-r rss] [-z vsz] [-P %cpu] [-a argument-array]
 [-C command] [-k] [-t timeout] [-v]

In the client's /etc/nagios/nrpe.cfg, I have this:

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command[check_procs]=/usr/lib64/nagios/plugins/check_procs -C $ARG1$ -c $ARG2$

If I change the client's nrpe.cfg file to this:

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command[check_procs]=/usr/lib64/nagios/plugins/check_procs -C $ARG1$

The command works.

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# /usr/local/nagios/libexec/check_nrpe -H <TARGET HOST> -c check_procs -a "sshd"
PROCS OK: 3 processes with command name 'sshd' | procs=3;;;0;

Why?

Re: check_nrpe -c check_procs Not Working

Posted: Tue Aug 18, 2020 2:30 pm

by benjaminsmith

Hi,

Not quite why it was working before or what changes were made, but the following error is related to the arguments not getting passed correctly.

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 /usr/local/nagios/libexec/check_nrpe -H <TARGET HOST> -t 30 -c check_procs -a "'-C sshd' '-c 1:'"
Usage:
check_procs -w <range> -c <range> [-m metric] [-s state] [-p ppid]
[-u user] [-r rss] [-z vsz] [-P %cpu] [-a argument-array]
[-C command] [-k] [-t timeout] [-v

One way to simplify this is to just use a single argument in your command definition and pass all the options in quote to the check_proces command for example. Change the command in nrpe.cfg to this:

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command[check_procs]=/usr/lib64/nagios/plugins/check_procs $ARG1$

And then run setup your command as follows:

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./check_nrpe -H 192.168.23.144 -c check_procs '-a  -C sshd -c 1:'

If you make any changes to nrpe.cfg, be sure to restart the nrpe service or xinetd, depending how it was installed. Let me know if that will work you.

Re: check_nrpe -c check_procs Not Working

Posted: Wed Aug 19, 2020 2:11 pm

by wrobj0

Unfortunately, I still can't quite get this working.

I forgot to put this in the original post, but here's the relevant version information:
Nagios Server:
Red Hat Enterprise Linux Server release 7.8 (Maipo)
Nagios XI 5.6.14

TARGET_HOSTs:
NRPE: Version: 2.15 OS: RHEL 6.10 and RHEL 7.7
NRPE: Version: 4.0.3 OS: CentOS8

Our Nagios configuration has this in it from some time long before I joined the team. If I add a new Linux host using the configuration wizard, it uses this check_nrpe command (I added the -2 a few months back because it was filling our logs with version errors, and I found some thread on here that said to do that).

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define command {
    command_name    check_nrpe
    command_line    $USER1$/check_nrpe -2 -H $HOSTADDRESS$ -t 30 -c $ARG1$
}

$ARG1$ = check_$CMD '-$OPTS'

In this specific instance, ARG1 = check_procs -a '-c 1:1024 -Csshd', but the vast majority of our services are configured in this way, like checking time drift is ARG1 = check_time -a '-w 15 -c 30'. Particularly troubling is that

Like I said, that worked for years, and I have no idea why or when it stopped. This is particularly worrisome because it was by chance that I caught this. That all services report OK in Nagios despite that almost 0 of the commands work is a massive failure from Nagios. My boards should be glowing red, and my email should be flooded with service failures, but it took me adding and testing a new check to find this. I'm not sure if you work for them, or if I should submit this feedback another way, but this needs to get fixed even if the syntax I'm using is no longer valid.

Some relevant excerpts from TARGET_HOST's nrpe config file
dont_blame_nrpe=1
include_dir=/etc/nrpe.d/

Contents of the config file in /etc/nrpe.d

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command[check_swap]=/usr/lib64/nagios/plugins/check_swap $ARG1$
command[check_disk]=/usr/lib64/nagios/plugins/check_disk $ARG1$
command[check_load]=/usr/lib64/nagios/plugins/check_load $ARG1$
command[check_procs]=/usr/lib64/nagios/plugins/check_procs $ARG1$
command[check_time]=/usr/lib64/nagios/plugins/check_ntp_time -H net-ntp00.uchicago.edu $ARG1$
command[check_zombie_procs]=/usr/lib64/nagios/plugins/check_procs -s Z $ARG1$
command[check_mem]=/etc/nagios/scripts/check_mem.sh $ARG1$
command[check_mount]=/etc/nagios/scripts/check_mount.sh
command[check_disk_stat]=/etc/nagios/scripts/check_diskstat.sh $ARG1$
command[check_network_stats]=/etc/nagios/scripts/stat_net.pl
command[check_cpu_stats]=/etc/nagios/scripts/check_cpu_stats.sh $ARG1$
command[check_openmanage]=/etc/nagios/scripts/check_openmanage $ARG1$

Trying your suggestion from the CLI:

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[root@nagios]#/usr/local/nagios/libexec/check_nrpe -H $TARGET_HOST -c check_procs '-a -C sshd -c 1:'
PROCS WARNING: 1 process with args '-C' | procs=1;sshd;1:;0;

This is incorrect, though. Actual sshd processes running on TARGET_HOST

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[root@TARGET_HOST]# pgrep sshd | wc -l
3

Figuring it probably sees options as arguments, I moved the first apostrophe over, and it works.

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[root@nagios]#/usr/local/nagios/libexec/check_nrpe -H $TARGET_HOST -c check_procs -a '-C sshd -c 1:'
PROCS OK: 3 processes with command name 'sshd' | procs=3;;1:;0;

Replicating this in the WebUI:

This fails no matter how I try to structure the syntax using this command

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define command {
    command_name    check_nrpe
    command_line    $USER1$/check_nrpe -2 -H $HOSTADDRESS$ -t 30 -c $ARG1$
}

So I created a new command called check_procs. I did this through the WebUI, after which I applied the conifguration.

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define command {
    command_name    check_procs
    command_line    $USER1$/check_nrpe -H $HOSTADDRESS$ -c check_procs $ARG1$ 
}

ARG1 = '-a -C sshd -c 1:'

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SQL Error [nagiosxi] : ERROR:  syntax error at or near "sshd"
LINE 1: ...TARGET_HOST -c check_procs \'-a -C sshd -c 1:...
                                                             ^

[nagios@nagios ~]$ /usr/local/nagios/libexec/check_nrpe -H aaaTARGET_HOST -c check_procs '-a -C sshd -c 1:'
Error submitting command

.

ARG1 = -a '-C sshd -c 1:'

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SQL Error [nagiosxi] : ERROR:  syntax error at or near "sshd"
LINE 1: ...TARGET_HOST -c check_procs -a \'-C sshd -c 1:...
                                                             ^

[nagios@nagios ~]$ /usr/local/nagios/libexec/check_nrpe -H aaaTARGET_HOST -c check_procs -a '-C sshd -c 1:'
Error submitting command.

So I modified this in TARGET_HOST's nrpe.cfg

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command[check_procs]=/usr/lib64/nagios/plugins/check_procs -a $ARG1$

I then updated the command in Nagios and applied the config again.

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define command {
    command_name    check_procs
    command_line    $USER1$/check_nrpe -H $HOSTADDRESS$ -c check_procs -a $ARG1$ 
}

ARG1 = -C sshd -c 1:

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[nagios@nagios ~]$ /usr/local/nagios/libexec/check_nrpe -H aaaTARGET_HOST -c check_procs -a -C sshd -c 1:

ARG1 = '-C sshd -c 1:'

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SQL Error [nagiosxi] : ERROR:  syntax error at or near "sshd"
LINE 1: ...TARGET_HOST -c check_procs -a \'-C sshd -c 1:...
                                                             ^

[nagios@nagios ~]$ /usr/local/nagios/libexec/check_nrpe -H aaaTARGET_HOST -c check_procs -a '-C sshd -c 1:'
Error submitting command.

That's broken from the CLI, too, so I guess it's just not good syntax.

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[root@nagios]#/usr/local/nagios/libexec/check_nrpe -H $TARGET_HOST -c check_procs -a '-C sshd -c 1:'
PROCS CRITICAL: 0 processes with args '-Csshd' | procs=0;;1:;0;

Re: check_nrpe -c check_procs Not Working

Posted: Wed Aug 19, 2020 2:17 pm

by wrobj0

I was trying to track down the date on which this stopped working, and I discovered that I received a critical notification on August 9.

I then decided to test alerting on a non-critical service, and found that the services are being monitored, it's just the check command part that's broken.

Re: check_nrpe -c check_procs Not Working

Posted: Thu Aug 20, 2020 3:13 pm

by benjaminsmith

Hi,

It's very close but there are a few things with the syntax to modify. On the host side,npre.cfg, set your command as follows:

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command[check_procs]=/usr/local/nagios/libexec/check_procs $ARG1$

Next in Nagios XI, change the check_nrpe command back to the default. You can add the -2 option to force version 2 packest in case you are setting up checks with systems running older versions of the NRPE agent. For example:

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$USER1$/check_nrpe -2 -H $HOSTADDRESS$ -t 30 -c $ARG1$ $ARG2$

We tested the command with the following syntax, and they are working.

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[root@main-nagios-xi libexec]# ./check_nrpe -H <ip address> -c check_procs -a '-C sshd -c 1:'
PROCS OK: 2 processes with command name 'sshd' | procs=2;;1:;0;

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[root@main-nagios-xi libexec]# ./check_nrpe -H <ip address> -c check_procs -a '-C sshd' -c 1:
PROCS OK: 2 processes with command name 'sshd' | procs=2;;;0;

In the CCM, the arguments should look like this in the Nagios XI CCM.

check-procs.png

Let us know if you get it working.

Re: check_nrpe -c check_procs Not Working

Posted: Tue Aug 25, 2020 5:54 pm

by wrobj0

It appears there's either a bug in the "Run Check Command" function causing it to fail when I use it, or there's something else somewhere in the configurations creating this problem.

I modified the command to work the way you suggested, and I get the same error.

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SQL Error [nagiosxi] : ERROR:  syntax error at or near "sshd"
LINE 1: ...2 -H TARGET_HOST -t 30 -c check_procs  -a \'-C sshd -c 1:...
                                                             ^

[[email protected] ~]$ /usr/local/nagios/libexec/check_nrpe -2 -H TARGET_HOST -t 30 -c check_procs  -a '-C sshd -c 1:'
Error submitting command.

So our existing monitoring is fine, at least in terms of service checks (our check_total_procs check is definitely broken on some hosts, but that check is pointless in our environment).

It's still super inconvenient to go back and forth between the WebUI and CLI, though, so what might cause the check command function to fail, despite identical configurations to yours?

Re: check_nrpe -c check_procs Not Working

Posted: Wed Aug 26, 2020 1:03 pm

by lmiltchev

I am not sure why this command is not working for you. It works for me just fine with the same arguments.

On the target machine, I have check_procs command defined as this:

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command[check_procs]=/usr/local/nagios/libexec/check_procs $ARG1$

Testing the plugin on the remove box:

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/usr/local/nagios/libexec/check_procs -C sshd -c 1:
PROCS OK: 2 processes with command name 'sshd' | procs=2;;1:;0;

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pgrep sshd | wc -l
2

On the Nagios XI, I have:

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define command {
    command_name    check_nrpe
    command_line    $USER1$/check_nrpe -2 -u -H $HOSTADDRESS$ -t 60 -c $ARG1$ $ARG2$
}

Testing from the CLI:

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/usr/local/nagios/libexec/check_nrpe -2 -u -H 192.168.x.x -t 60 -c check_procs -a '-C sshd -c 1:'
PROCS OK: 2 processes with command name 'sshd' | procs=2;;1:;0;

In the GUI:

example-01.jpg

example-02.jpg

Try the following:

1. Check your db log for errors/crashed tables, and repair the db.
https://assets.nagios.com/downloads/nag ... tabase.pdf

2. Make sure your plugin works locally (on the target machine):

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/usr/lib64/nagios/plugins/check_procs -C sshd -c 1:

3. Make sure that your command is defined as this:

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command[check_procs]=/usr/lib64/nagios/plugins/check_procs $ARG1$

and there are no other definitions of the same command in the include directory (/etc/nrpe.d) or any other place.

4. Restart NRPE daemon on the target machine after making the changes. If NRPE is not running as a standalone daemon, you may need to restart xinetd instead.

5. Test your command from the CLI and the GUI on the Nagios XI server.

If you continue to have issues, we may need to move this to our ticketing system, and schedule a remote session.