Creating a custom Nagios function

Nagios Exit Codes
Exit Code Status
0 OK
1 WARNING
2 CRITICAL
3 UNKNOWN
Create the Script to be added as the Plugin

#!/bin/bash
used_space=`df -h / | grep -v Filesy | awk '{print $5}' | sed 's/%//g'`
case $used_space in
[1-84]*)
echo "OK - $used_space% of disk space used."
exit 0
;;
[85]*)
echo "WARNING - $used_space% of disk space used."
exit 1
;;
[86-100]*)
echo "CRITICAL - $used_space% of disk space used."
exit 2
;;
*)
echo "UNKNOWN - $used_space% of disk space used."
exit 3
;;
esac

try to put the script in same plugin directory with the other ones
/usr/lib/nagios/plugins/

make it executable
Add Your New Command to Nagios Checks on Nagios Monitoring Server

Define new command in /etc/nagios/objects/commands.cfg
define command{
command_name usedspace_bash
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c usedspace_bash
}
Add Your Script to NRPE configuration on client host
command[usedspace_bash]=/usr/lib/nagios/plugins/usedspace.sh

 

adding to configuration
/etc/nagios/servers/<name-0f-config>.cfg
define service {
use generic-service
host_name Hostname
service_description Custom Disk Checker In Bash
check_command usedspace_bash
}

 

 

Adding ESXI to Nagios

yum install perl-Pod-Perldoc perl-CPAN openssl-devel
# wget http://dl.fedoraproject.org/pub/epel/6/i386/perl-Nagios-Plugin-0.35-1.el6.noarch.rpm
# wget http://mirror.centos.org/centos/6/os/i386/Packages/perl-Config-Tiny-2.12-7.1.el6.noarch.rpm
# wget http://mirror.centos.org/centos/6/os/i386/Packages/perl-Params-Validate-0.92-3.el6.i686.rpm
# rpm -ivh perl-Nagios-Plugin-0.35-1.el6.noarch.rpm perl-Config-Tiny-2.12-7.1.el6.noarch.rpm perl-Params-Validate-0.92-3.el6.i686.rpm
# cd /root
# tar xvzf VMware-vSphere-Perl-SDK-4.1.0-254719.i386.tar.gz
# cd vmware-vsphere-cli-distrib/
# ./vmware-install.pl

# cd /usr/lib/nagios/plugins/
Download check_esx3.pl and make it executable
http://exchange.nagios.org/components/com_mtree/attachment.php?link_id=2154&cf_id=29
chmod +x check_esx3.pl


vim /usr/local/nagios/etc/objects/vmware.cfg
First define all your hosts as shown below

# Host esx01
define host{
use vmware-server
host_name esxi01
alias VMWare ESXi 01
address IP Address
}
define host{
use vmware-server
host_name esxi02
alias VMWare ESXi 02
address IP Address
}
# Similarly you can define all the hosts

# Now define a hostgroup for your Esxi Hosts:

define hostgroup{
hostgroup_name Esxi-Servers ; The name of the hostgroup

alias Vmware Servers ; Long name of the group

members esxi01,esxi02
}

# Now create the service definition as shown below
# check cpu
define service{
use generic-service
host_name esxi01
service_description ESXi CPU Load
check_command check_esx_cpu!80!90
}

# check memory usage
define service{
use generic-service
host_name esxi01
service_description ESXi Memory usage
check_command check_esx_mem!80!90
}

# check net
define service{
use generic-service
host_name esxi01
service_description ESXi Network usage
check_command check_esx_net!102400!204800
}

# check runtime status
define service{
use generic-service
host_name esxi01
service_description ESXi Runtime status
check_command check_esx_runtime
}

# check io read
define service{
use generic-service
host_name esxi01
service_description ESXi IO read
check_command check_esx_ioread!40!90
}

# check io write
define service{
use generic-service
host_name esxi01
service_description ESXi IO write
check_command check_esx_iowrite!40!90
}

Define the commands related to ESXi in the /usr/local/nagios/etc/objects/command.cfg file

vim /usr/local/nagios/etc/objects/commands.cfg
# check vmware esxi machine
# check cpu
define command{
command_name check_esx_cpu
command_line $USER1$/check_esx -H $HOSTADDRESS$ -u $USER11$ -p $USER12$ -l cpu -s usage -w $ARG1$ -c $ARG2$
}

# check memory usage
define command{
command_name check_esx_mem
command_line $USER1$/check_esx -H $HOSTADDRESS$ -u $USER11$ -p $USER12$ -l mem -s usage -w $ARG1$ -c $ARG2$
}

# check net usage
define command{
command_name check_esx_net
command_line $USER1$/check_esx -H $HOSTADDRESS$ -u $USER11$ -p $USER12$ -l net -s usage -w $ARG1$ -c $ARG2$
}

# check runtime status
define command{
command_name check_esx_runtime
command_line $USER1$/check_esx -H $HOSTADDRESS$ -u $USER11$ -p $USER12$ -l runtime -s status
}

# check io read
define command{
command_name check_esx_ioread
command_line $USER1$/check_esx -H $HOSTADDRESS$ -u $USER11$ -p $USER12$ -l io -s read -w $ARG1$ -c $ARG2$
}

# check io write
define command{
command_name check_esx_iowrite
command_line $USER1$/check_esx -H $HOSTADDRESS$ -u $USER11$ -p $USER12$ -l io -s write -w $ARG1$ -c $ARG2$
}

Adding configuration to nagios

vim /usr/local/nagios/etc/nagios.cfg
cfg_file=/usr/local/nagios/etc/objects/vmware.cfg

Nagios- Setting up

This guide explains how to set up a client server to be monitored by Nagios. We'll cover installing the necessary Nagios plugins and the NRPE (Nagios Remote Plugin Executor) agent, which allows the Nagios server to run checks on the client.

---

PREREQUISITES

Before you start, make sure you have:

• A Linux-based client server.

• Root access or sudo privileges.

• Basic understanding of the Linux command line.

---

INSTALLING NAGIOS PLUGINS

Nagios plugins are scripts that perform checks on various aspects of your server, like disk space, CPU usage, or running services.

1. Prepare the Environment:

   • Navigate to a temporary directory: cd /usr/local/src/

   • Create a directory for Nagios files: mkdir nagios

   • Move into the new directory: cd nagios

   • Create a nagios user: useradd nagios

2. Download and Extract Plugins:

   • Download the plugins: wget http://pkgs.fedoraproject.org/repo/pkgs/nagios-plugins/nagios-plugins-1.4.16.tar.gz/862f5e44fb5bc65ce7e5d86d654d4da0/nagios-plugins-1.4.16.tar.gz

   • Extract the downloaded file: tar -xzf nagios-plugins-1.4.16.tar.gz

   • Change into the extracted directory: cd nagios-plugins-1.4.16

3. Compile and Install Plugins:

   • Set a required environment variable: export LDFLAGS=-ldl

   • Configure the installation: ./configure --with-nagios-user=nagios --with-nagios-group=nagios --enable-redhat-pthread-workaround --enable-ssl

   • Compile the plugins: make

   • Install them: make install

   • Go back to the parent directory: cd ..

---

INSTALLING NRPE (NAGIOS REMOTE PLUGIN EXECUTOR)

NRPE allows your Nagios server to execute the plugins you just installed on this client.

1. Download and Extract NRPE:

   • Download NRPE: wget http://sourceforge.net/projects/nagios/files/nrpe-2.x/nrpe-2.13/nrpe-2.13.tar.gz/download

   • Extract the file: tar -xzf nrpe-2.13.tar.gz

   • Change into the extracted directory: cd nrpe-2.13

2. Compile and Install NRPE:

   • Configure NRPE: ./configure

   • Compile all components: make all

   • Install the NRPE plugin for the Nagios server (even though this is a client, it's good practice): make install-plugin

   • Install the NRPE daemon (the service that runs on the client): make install-daemon

   • Install the default NRPE configuration file: make install-daemon-config

   • Install NRPE to run under xinetd (a service that manages other services): make install-xinetd

---

CONFIGURE XINETD AND NRPE

NRPE often runs through xinetd, which listens for incoming connections and starts the NRPE daemon when needed.

1. Install and Restart Xinetd:

   • Install xinetd if it's not already present: yum install xinetd (or apt-get install xinetd for Debian/Ubuntu)

   • Restart xinetd to apply changes: service xinetd restart

2. Add NRPE Service to System Services:

   • Add the NRPE service and its default port (5666) to the /etc/services file: echo "nrpe 5666/tcp # NRPE" >> /etc/services

---

FIREWALL CONFIGURATION

You need to open port 5666 on the client's firewall so the Nagios server can communicate with NRPE.

• For CSF (Config Server Firewall) Users:

  • Edit the CSF configuration file: /etc/csf/csf.conf

  • Find the TCP_IN section and add 5666 to the list of allowed incoming TCP ports.

  • Restart CSF: This usually involves csf -r or service csf restart.

---

NRPE CONFIGURATION AND SECURITY

You must specify which Nagios servers are allowed to connect to this NRPE agent.

• Allow Nagios Server IP:

  • Edit the xinetd configuration for NRPE: /etc/xinetd.d/nrpe

  • Edit the main NRPE configuration file: /usr/local/nagios/etc/nrpe.cfg

  • In both files, locate the allowed_hosts directive and add the IP address of your Nagios monitoring server. For example: allowed_hosts = 127.0.0.1, <YOUR_NAGIOS_SERVER_IP>

---

SETTING A PASSWORD FOR THE NAGIOS USER (Optional but Recommended)

It's good practice to set a password for the nagios user created earlier.

• Set password: passwd nagios

---

NAGIOS SERVER CONFIGURATION EXAMPLE (for MySQL Monitoring)

This section shows an example of how you would configure a service check on your Nagios server to monitor a MySQL database on this client. This is done on the Nagios server, not the client.

define service{
    use                     local-service       ; Name of service template to use
    host_name               sample.example.com  ; The hostname of your client server
    service_description     mySQL               ; A description of the service being monitored
    is_volatile             0
    check_period            24x7
    max_check_attempts      20
    normal_check_interval   5                   ; Check every 5 minutes
    retry_check_interval    1                   ; Retry every 1 minute on failure
    notification_options    w,u,c,r             ; Notify on warning, unknown, critical, recovery
    notification_interval   960                 ; Notify every 960 minutes (16 hours)
    notification_period     24x7
    check_command           check_mysql!nagios!password@666# ; The command to run, 

                    ;including username and password
}

Note: Replace sample.example.com with your client's hostname and adjust nagios and password@666# if your MySQL user or password differs.