NSCA Server - CentOS 6.5 and Nagios Core 4.0.x

Overview

This guide will show you how to install NSCA on a Nagios Core 4.0.x host running on CentOS 6.5.

At the end of this guide, Nagios will be listening for check results submitted from external hosts.

Install NSCA

Establish an ssh session to your Nagios host as the user root

Type:

yum -y install gcc xinetd

Wait while the components are downloaded/updated

Type:

cd /tmp

Type:

wget http://prdownloads.sourceforge.net/sourceforge/nagios/nsca-2.9.1.tar.gz

Wait while the file is downloaded

Type:

tar xzf nsca-2.9.1.tar.gz

Type:

cd nsca-2.9.1

Type:

./configure

Wait while the "configure" procedure is run

Type:

make all

Wait while the "make all" procedure is run

Type:

cp src/nsca /usr/local/nagios/bin

Type:

cp sample-config/nsca.cfg /usr/local/nagios/etc

Type:

chown nagios.nagcmd /usr/local/nagios/etc/nsca.cfg

Type:

chmod g+r /usr/local/nagios/etc/nsca.cfg

Type:

cp src/send_nsca /usr/local/nagios/libexec

Type:

cp sample-config/send_nsca.cfg /usr/local/nagios/etc

Type:

cp sample-config/nsca.xinetd /etc/xinetd.d/nsca

The following three commands allow inbound TCP traffic on port 5667.

Type:

echo 'nsca    5667/tcp    #NSCA' >> /etc/services

Type:

iptables -I INPUT -p tcp --destination-port 5667 -j ACCEPT

Type:

service iptables save

Type:

chkconfig xinetd on

At this point NSCA is installed, but still needs to be configured.

Configure NSCA

Before we can start the NSCA service we need to define some configuration settings.

These are the security settings:

Type:

nano /usr/local/nagios/etc/nsca.cfg

A password needs to be defined that the sending clients use

Change:

#password=

To:

password=Passw0rd

That's a pretty basic password, you should pick something better!

A decryption method also needs to be defined, however the default is 1 (Simple XOR) and we'll leave it at that for the moment

decryption_method=1

Press Ctrl + X

Type:

Y

Press Enter to save changes

These are the service settings:

Type:

nano /etc/xinetd.d/nsca

You need to allow what hosts can submit results.

This can be an IP Address:

10.25.254.16

It it could be a Subnet:

10.25.0.0/16

In my scenario I'm allowing the localhost AND a subnet.

Change:

only_from    = 127.0.0.1

To:

only_from    = 127.0.0.1 10.25.0.0/16

Press Ctrl + X

Type:

Y

Press Enter to save changes

Start NSCA

Type:

service xinetd start

Test NSCA

A simple NSCA client is also installed as part of NSCA so we can do a simple test to ensue it works. First it needs configuring:

Type:

nano /usr/local/nagios/etc/send_nsca.cfg

A password needs to be defined that the sending clients use

Change:

#password=

To:

password=Passw0rd

That's a pretty basic password, you should pick something better!

A encryption method also needs to be defined, however the default is 1 (Simple XOR) and we'll leave it at that for the moment

encryption_method=1

Press Ctrl + X

Type:

Y

Press Enter to save changes

Now we are going to create a simple check result in a file

Type:

nano /tmp/nsca_test

Type:

localhost

Press TAB key

Type:

Test Result

Press TAB key

Type:

1

Press TAB key

Type:

This is the test result with a WARNING status

NOTE: Those are tabs separating the fields, what you typed is:

localhost[TAB]Test Service[TAB]1[TAB]This is the test result with a WARNING status

Press Ctrl + X

Type:

Y

Press Enter to save changes

Now we are going to submit that simple check result

Type:

/usr/local/nagios/libexec/send_nsca -H 127.0.0.1 -p 5667 -c /usr/local/nagios/etc/send_nsca.cfg < /tmp/nsca_test

You should receive a response like:

1 data packet(s) sent to host successfully.

In addition to this, you will see the passive check result in the nagios log:

[1419031130] EXTERNAL COMMAND: PROCESS_SERVICE_CHECK_RESULT;localhost;Test Service;1;This is the test result with a WARNING status
[1419031130] Warning:  Passive check result was received for service 'Test Service' on host 'localhost', but the service could not be found!
[1419031130] Error: External command failed -> PROCESS_SERVICE_CHECK_RESULT;localhost;Test Service;1;This is the test result with a WARNING status
[1419031130] External command error: Command failed

The errors are simply because there is no passive service called "Test Service" for the host localhost, this is expected.

Summary

At this point NSCA is now installed and configured. In the example above, it will accept checks from 127.0.0.1 AND the subnet 10.25.0.0/16.

Final Thoughts

For any support related questions please visit the Nagios Support Forums at:

http://support.nagios.com/forum/