How to Create Own Nagios Plugin using Bash Shell Script

    RahulBy 2 Mins ReadUpdated:

    How to Create Own Nagios Plugin using Bash Shell Scripts. This is useful for monitoring infrastructure as your own setup. This tutorial will help you to understand, how to write a script and use them with NRPE and Nagios for monitoring.

    Step 1 – Understand Return Codes

    Every Nagios plugin must return with a status code which is called return code. On the basis of return codes, Nagios core service takes decisions and appropriate action for the corresponding host or service.

    Hosts:

    Return Code / Host status
    0 => UP
    1 => DOWN
    Other Maintains last known state

    Services:
    Return code / Service status
    0 => OK
    1 => WARNING
    2 => CRITICAL
    3 => UNKNOWN
    Other CRITICAL : unknown return code

    Step 2 – Install NRPE Client

    Let’s install the NRPE client on your system using the following commands.

    sudo apt-get update
sudo apt-get install nagios-nrpe-server nagios-plugins

    The above commands are for Debian based systems. To install NRPE on Redhat based system, visit this tutorial.

    Step 3 – Write A Shell Script

    Now the time to write a shell script to monitor any service on your system. For this example below script will monitor the disk space uses.

    vim /usr/lib/nagios/plugins/check_disk_uses.sh

    Add the below script.

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    #!/bin/bash
     
    ### ======================================================================= ###
    ###     A nagios plugin to check disk uses for given disk or mountpoint     ###
    ###     Uses: ./check_disk_uses.sh /                                        ###
    ###           ./check_disk_uses.sh /mnt                                     ###
    ###           ./check_disk_uses.sh /dev/sda1                                ###
    ### ======================================================================= ###
     
    ### ======================================================================= ###
    ###                         FUNCTIONS                                       ###
    ### ======================================================================= ###
     
    calculate_disk_uses(){
    USED_DISK_SPACE=`df -h ${MOUNT_POINT} | grep -v Filesystem | awk '{print $5}' | sed 's/%//g'`
    case ${USED_DISK_SPACE} in
    [1-80]*)
    echo "OK - ${USED_DISK_SPACE}% of disk space used."
    exit 0
    ;;
    [81-85]*)
    echo "WARNING - ${USED_DISK_SPACE}% of disk space used."
    exit 1
    ;;
    [86-100]*)
    echo "CRITICAL - ${USED_DISK_SPACE}% of disk space used."
    exit 2
    ;;
    *)
    echo "UNKNOWN - ${USED_DISK_SPACE}% of disk space used."
    exit 3
    ;;
    esac
    }
     
    ### ======================================================================= ###
    ###                         SCRIPT EXECUTION START HERE                     ###
    ### ======================================================================= ###
     
    if [[ -z "$1" ]]
    then
            echo "Missing parameters! Syntax: ./`basename $0` mount_point/disk"
            exit 3
    else
            MOUNT_POINT=$1
    fi
     
    calculate_disk_uses
     
    ### ======================================================================= ###
    ###                         END OF SCRIPT                                   ###
    ### ======================================================================= ###

    Now set the execute permission on the new script.

    chmod +x /usr/lib/nagios/plugins/check_disk_uses.sh

    Step 4 – Update NRPE Configuration

    Now edit NRPE configuration file /etc/nagios/nrpe.cfg and add your command to monitor some disk of your system.

    command[check_disk_uses]=/usr/lib/nagios/plugins/check_disk_uses.sh /dev/sda1

    You can call check_disk_uses command from Nagios server using check_nrpe command and get the results back.

    Step 5 – Test with Check_Nrpe Command

    Now, run the below command from your Nagios server, where 192.168.1.100 is the IP of the NRPE client system.

    ./check_nrpe -H 192.168.1.100 -c check_disk_uses

OK - 22% of disk space used.
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    1 Comment

    1. Dupont on

      Hello,

      I have a problem with this tutorial. I have a version 3 for check_nrpe. I have a message “check_disk_uses not defined since the server centreon.I have add the command on the file nrpe.cfg, enable to 1 to “dont_blame_nrpe” . Since the client machine (debian) our command works proprely.
      Do you have a solution ?

      Thanks for our answer.

      Reply

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