Strictly speaking, this is not an article i wrote myself. I am here simply combine this up for my conveniences and for people who visited this blog [ there are just too many article flying around for me to search each time 🙁 ]. I am using Centos 5.5
Easy way to install Nagios
Apparently there is a simple way via yum
yum install epel-release
yum install nagios nagios-devel nagios-plugins* gd gd-devel httpd php gcc glibc glibc-common
Above will install all nagios required plugins and the only thing you will need to do is to install apache to get it up.
Installing Nagios on the Monitoring server
Please refer to the quick installation guide at http://nagios.sourceforge.net/docs/3_0/quickstart-fedora.html
Nagios Monitoring Server
Downlad and Install NRPE Plugin
# mkdir -p /opt/Nagios/Nagios_NRPE
# cd /opt/Nagios/Nagios_NRPE
Save file to directory /opt/Nagios
http://www.nagios.org/download/download.php
As of this writing NRPE 2.12 (Stable)
Extract the Files:
# tar -xzf nrpe-2.12.tar.gz
# cd nrpe-2.12
Compile and Configure NRPE
# ./configure
# make all
# make install-plugin
Test Connection to NRPE daemon on Remote Server
Lets now make sure that the NRPE on our Nagios server can talk to the NRPE daemon on the remote server we want to monitor. Replace “” with the remote servers IP address. Please take note that must be a remote IP address that you wish to monitor. At this point of time, you may not have any such server. Hence, you can skip this if you wish to.
# /usr/local/nagios/libexec/check_nrpe -H
NRPE v2.12
Create NRPE Command Definition
A command definition needs to be created in order for the check_nrpe plugin to be used by nagios.
# vi /usr/local/nagios/etc/objects/commands.cfg
Add the following:
###############################################################################
# NRPE CHECK COMMAND
#
# Command to use NRPE to check remote host systems
###############################################################################
define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}
Create Linux Object template
In order to be able to add the remote linux machine to Nagios we need to create an object template file adn add some object definitions.
Create new linux-box-remote object template file:
# vi /usr/local/nagios/etc/objects/linux-box-remote.cfg
Add the following and replace the values “host_name” “alias” “address” with the values that match your setup:
** The “host_name” you set for the “define_host” section must match the “host_name” in the “define_service” section **
define host{
name linux-box-remote ; Name of this template
use generic-host ; Inherit default values
check_period 24x7
check_interval 5
retry_interval 1
max_check_attempts 10
check_command check-host-alive
notification_period 24x7
notification_interval 30
notification_options d,r
contact_groups admins
register 0 ; DONT REGISTER THIS - ITS A TEMPLATE
}
define host{
use linux-box-remote ; Inherit default values from a template
host_name Centos5 ; The name we're giving to this server
alias Centos5 ; A longer name for the server
address 192.168.0.5 ; IP address of the server
}
define service{
use generic-service
host_name Centos5
service_description CPU Load
check_command check_nrpe!check_load
}
define service{
use generic-service
host_name Centos5
service_description Current Users
check_command check_nrpe!check_users
}
define service{
use generic-service
host_name Centos5
service_description /dev/hda1 Free Space
check_command check_nrpe!check_hda1
}
define service{
use generic-service
host_name Centos5
service_description Total Processes
check_command check_nrpe!check_total_procs
}
define service{
use generic-service
host_name Centos5
service_description Zombie Processes
check_command check_nrpe!check_zombie_procs
}
Activate the linux-box-remote.cfg template:
# vi /usr/local/nagios/etc/nagios.cfg
And add:
# Definitions for monitoring remote Linux machine
cfg_file=/usr/local/nagios/etc/objects/linux-box-remote.cfg
Next you will need to add nrpe onto your command list.
[root@ns ~]# vi /etc/nagios/objects/commands.cfg
# add at the bottom
define command{
command_namecheck_nrpe
command_line$USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}
this will allow you to use the command check_nrpe.
Verify Nagios Configuration Files:
# /usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg
Total Warnings: 0
Total Errors: 0
Restart Nagios:
# service nagios restart
Check Nagios Monitoring server that the remote linux box was added and is being monitored !
Nagios Monitored Server
This is the setting for ALL of your monitored servers (Server that you want to be monitor by the central monitoring server)
Firstly, install the required package.
yum install gcc glibc glibc-common gd gd-devel openssl-devel make
Setup the users
Just setup nagios as a user to execute all nagios instruction later
useradd nagios
passwd nagios
add your own password.
Download and Install Nagios Plugins
go to your src folder and download all the required nagios stuff which is nagios plugin and nrpe. Both plugin and nrpe is located at http://www.nagios.org/download/download.php. find the link and wget it like i show below.
here's the link of the two nagios required plugins
- http://www.nagios.org/download/plugins/
- http://exchange.nagios.org/directory/Addons/Monitoring-Agents/NRPE-%252D-Nagios-Remote-Plugin-Executor/details
cd /usr/local/src/
wget http://prdownloads.sourceforge.net/sourceforge/nagiosplug/nagios-plugins-1.4.15.tar.gz
wget http://prdownloads.sourceforge.net/sourceforge/nagios/nrpe-2.12.tar.gz
Once download is completed, tar both files
tar xzf nagios-plugins-1.4.15.tar.gz
tar xzf nrpe-2.12.tar.gz
Compile and Configure Nagios Plugins
We will need to install the openssl library before installing them
yum install -y openssl-devel
Once you install and tar both files, its time to install them.
cd nagios-plugins-1.4.15
./configure --with-nagios-user=nagios --with-nagios-group=nagios
make
make install
chown nagios.nagios /usr/local/nagios
chown -R nagios.nagios /usr/local/nagios/libexec
Now, we will need to install xinetd to ensure it is secure.
yum install -y xinetd
Next, we will need to configure xinetd to allow certain port and nrpe.
Install NRPE Daemon
Time to install NRPE Daemon!
cd nrpe-2.12
./configure
make all
make install-plugin
make install-daemon
make install-daemon-config
make install-xinetd
We will need to confiure xinetd now.
Post NRPE Configuration
Edit Xinetd NRPE entry:
Add Nagios Monitoring server to the "only_from" directive
vi /etc/xinetd.d/nrpe
find only_from directive and add your nagios monitoring server ip address so that the monitoring server can access your monitored server.
only_from = 127.0.0.1
Edit services file entry:
Add entry for nrpe daemon
vi /etc/services
add nrpe into the list.
nrpe 5666/tcp # NRPE
lastly restart the service and make it start on boot time.
chkconfig xinetd on
service xinetd restart
Open Firewall port for NRPE
Next, we will need to open up the firewall
vi /etc/sysconfig/iptables
add 5666 to your whitelist
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 5666 -j ACCEPT
Its time to test!
Test NRPE Daemon Install
Check NRPE daemon is running and listening on port 5666:
netstat -at |grep nrpe
Output should be:
tcp 0 0 *:nrpe *.* LISTEN
Check NRPE daemon is functioning:
/usr/local/nagios/libexec/check_nrpe -H localhost
Output should be NRPE version:
NRPE v2.12
Monitoring MySQL Server With Nagios
Nagios Ping /bin/ping Unknown status problem
This is simply a permission problem caused by the script /bin/ping. Hence, all you need to do is the following,
chmod u+s /bin/ping
After a while, nagios should be able to ping your server ip.
TroubleShooting
NRPE ./configure error:
checking for SSL headers… configure: error: Cannot find ssl headers
Solution:
You need to install the openssl-devel package
# yum -y install openssl-devel
CHECK_NRPE: Error – Could not complete SSL handshake
Solution:
This is most likely not a probem with SSL but rather with Xinetd access restrictions.
Check the following files:
/etc/xinetd.d/nrpe
/etc/hosts.allow
/etc/hosts.deny
no acceptable c compiler found in $PATH
When I gave the ./configure command i got this error saying: no acceptable c compiler found in $PATH and then it stops.
After a quick google search I found a topic saying that i needed to install gcc so i entered:
yum install gcc glibc glibc-common gd gd-devel
Hope it helps, you if need any web hosting solutions or have any question, feel free to pm me 🙂
