Nagios Support Forum

Hello. I have been working with Nagios Xi for a short time. I am trying to setup monitoring of our ERP system and I am running into a problem when I try running a check_disk command. Here are the software versions.
Server OS: centos:linux:6:GA
Client Host OS: RHEL 4
libmcrypt-2.5.0.52-49.ent.src.rpm
linux-nrpe-agent-el4

NRPE seems to work OK.
From the client: check_nrpe -H localhost returns NRPE v2.12
From the server: ./check_nrpe -H 10.206.201.25 returns NRPE v2.12

The check_disk command seems to work OK on the client: check_disk -w 20% -c 10% returns DISK OK - free space / 21211 MB (69% inode=96%); ...... etc.

But when I try to run the check_disk command with the check_nrpe command on the client check_nrpe -H localhost check_disk -a '-w 20% -c 10% -p /' -n
I get the error message: CHECK_NRPE: Error receiving data from daemon.

When I check the /var/log/messages file on the client I see:
May 7 15:50:45 trans4m nrpe[30987]: Error: Could not complete SSL handshake. 1

I thought that the -n option on the check_nrpe command told nrpe to not use SSL. So why is it complaining about an incomplete SSL handshake?

Any help would be greatly appreciated.

You need to define the host address for the remote host, as well as (-c) for the check command, like so:
Or depending on if you are using SSL or not:

I am testing this logged in to the client as nagios. I have set a path to the check_nrpe command directory for nagios so I ran this command

check_nrpe -H localhost -c check_disk -a '-w 20% -c 10% -p /' -n (I think I was using the -c option before, but missed it when I submitted the question)

Still got the CHECK_NRPE: Error receiving data from daemon.
Checked the /var/log/messages file with a tail and see Error: Could not complete SSL handshake. 1

If I try the command without the -n option I get the error NRPE: Unable to read output
But the error in the /var/log/messages is still Could not complete SSL handshake.

Am I misunderstanding the -n option? I am thinking that it should tell check_nrpe not to try and use SSL. I thought that using nrpe made it unnecessary to use SSL.

How is the "check_disk" command defined on the remote box?

There is a non-text file in /usr/local/nagios/libexec.
-bash-3.00# ls -al check_disk
-rwxr-xr-x 1 nagios nagios 280566 May 6 15:19 check_disk

I can run it with no problem.
bash-3.00# ./check_disk -w 20% -c 10%
ISK OK - free space: / 20998 MB (68% inode=96%); /NTN 25722 MB (39% inode=94%); /boot 83 MB (88% inode=99%); /dev/shm 1013 MB (100%
inode=99%);| /=9533MB;25732;28948;0;32165 /NTN=39167MB;54689;61525;0;68362 /boot=10MB;78;88;0;98 /dev/shm=0MB;810;911;0;1013

The problem occurs when I run it through the check_nrpe command.
-bash-3.00# ./check_nrpe -H localhost -c check_disk -a '-w 20% -c 10%' -n
CHECK_NRPE: Error receiving data from daemon.

The system logs say
-bash-3.00# tail /var/log/messages
May 15 09:08:06 trans4m nrpe[11116]: Error: Could not complete SSL handshake. 1
May 15 09:08:08 trans4m nrpe[11122]: Error: Could not complete SSL handshake. 1
May 15 09:08:17 trans4m nrpe[11155]: Error: Could not complete SSL handshake. 1
May 15 09:08:17 trans4m nrpe[11156]: Error: Could not complete SSL handshake. 1
May 15 09:08:27 trans4m nrpe[11185]: Error: Could not complete SSL handshake. 1
May 15 09:08:58 trans4m nrpe[11233]: Error: Could not complete SSL handshake. 1
May 15 09:08:59 trans4m nrpe[11238]: Error: Could not complete SSL handshake. 1
May 15 09:09:37 trans4m nrpe[11335]: Error: Could not complete SSL handshake. 1

I thought that the -n option made SSL unnecessary?

Checked the /usr/local/nagios/etc/
command[check_disk]=/usr/local/nagios/libexec/check_disk -w $ARG1$ -c $ARG2$ -p $ARG3$

Made sure that the allowed_hosts in /usr/local/nagios/etc/nrpe.cfg contained the localhost and the server.

Made sure that the only_from line in the /etc/xinetd.d/nrpe file includes the localhost and the server.

Tried it again and got the same result.
-bash-3.00# ./check_nrpe -H localhost -c check_disk -a '-w 20% -c 10%' -n
CHECK_NRPE: Error receiving data from daemon.
-bash-3.00# tail /var/log/messages
May 15 10:07:06 trans4m snmpd[2420]: transport socket = 12
May 15 10:07:09 trans4m nrpe[21056]: Error: Could not complete SSL handshake. 1
May 15 10:08:06 trans4m nrpe[21200]: Error: Could not complete SSL handshake. 1
May 15 10:08:08 trans4m nrpe[21201]: Error: Could not complete SSL handshake. 1
May 15 10:08:13 trans4m nrpe[21204]: Error: Could not complete SSL handshake. 1
May 15 10:08:17 trans4m nrpe[21222]: Error: Could not complete SSL handshake. 1
May 15 10:08:17 trans4m nrpe[21224]: Error: Could not complete SSL handshake. 1
May 15 10:08:27 trans4m nrpe[21256]: Error: Could not complete SSL handshake. 1

Closing this thread as you have a duplicate open in the Customer Forums. Please do not create two threads for the same issue.