In the first article, we have explained how to install and configure Nagios core on Amazon Linux Server. In this blog, we will show you how to add Linux host to Nagios monitoring server using nrpe plugin. Assuming you have already installed Nagios Server and running properly, if not please check Step By Step method for installing Nagios in Amazon Linux Once you have setup/installed Nagios Monitoring Server. Now you are ready to add remote Linux host for monitoring. Steps on Remote Linux Host which you want to monitor in Nagios monitoring server.
Install NRPE Add-on and Nagios Plugins on remote Linux host:
rpm -ivh https://dl.fedoraproject.org/pub/epel/epel-release-latest-6.noarch.rpm yum install -y nrpe nagios-plugins-all
Add Nagios servers IP address, separated by a comma as mention below.
vim /etc/nagios/nrpe.cfg allowed_hosts=127.0.0.1,Nagios_Server_IP
Configure Nagios Monitoring Checks:
How to monitor CPU usage, disk usage and total process in Nagios monitoring server. In this example, we will monitor Root Partition, Another disk usage like /mnt (additional disk), CPU load, User logged in, Total processes Login to your Linux host and edit nrpe.cfg file
vi /etc/nagios/nrpe.cfg command[check_users]=/usr/lib64/nagios/plugins/check_users -w 5 -c 10 command[check_load]=/usr/lib64/nagios/plugins/check_load -w 15,10,5 -c 30,25,20 command[check_disk]=/usr/lib64/nagios/plugins/check_disk -w 20% -c 10% -p /dev/sda1 command[check_mnt_disk]=/usr/lib64/nagios/plugins/check_mnt_disk -w 20% -c 10% -p /dev/xvdf command[check_zombie_procs]=/usr/lib64/nagios/plugins/check_procs -w 5 -c 10 -s Z command[check_total_procs]=/usr/lib64/nagios/plugins/check_procs -w 150 -c 200
#Note: In the above command definition -w stands for warning and -c stands for critical
Verify Nagios plugin:
/usr/lib64/nagios/plugins/check_procs -w 150 -c 200
Output PROCS WARNING: 190 processes | procs=190;150;200;0;
Command to start nrpe service on Linux host:
service nrpe start/restart/stop
Auto start nrpe service after reboot on Linux host:
chkconfig nrpe on
Steps to be done on Nagios Monitoring Server Login to your Nagios Monitoring Server.
Steps to Install NRPE Plugins on Nagios Server
rpm -ivh https://dl.fedoraproject.org/pub/epel/epel-release-latest-6.noarch.rpm yum install -y nrpe nagios-plugins-all
Verify NRPE plugins can communicate with your remote Linux host
/usr/lib64/nagios/plugins/check_nrpe -H ---Output---- NRPE v2.15
You will get output with NRPE version which is installed on a remote Linux host Tip:
- Make sure your firewall allows the communication between remote Linux host and Nagios monitoring host (vice versa)
- Check NRPE plugins installed properly with all dependency
How to add remote Linux host to Nagios Monitoring Server
Login to your Nagios monitoring server
Step 1: Uncomment below the line in “nagios.cfg” file
Here we specify the location of all your remote host file.
vi /usr/local/nagios/etc/nagios.cfg ... #Uncomment below the line cfg_dir=/usr/local/nagios/etc/servers ...
Step 2: Update/Add host definition in “templates.cfg”
vi /usr/local/nagios/etc/objects/templates.cfg
# Linux host definition template - This is NOT a real host, just a template!
define host{
name linux-server ; The name of this host template
use generic-host ; This template inherits other values from the generic-host template
check_period 24x7 ; By default, Linux hosts are checked round the clock
check_interval 5 ; Actively check the host every 5 minutes
retry_interval 1 ; Schedule host check retries at 1 minute intervals
max_check_attempts 10 ; Check each Linux host 10 times (max)
check_command check-host-alive ; Default command to check Linux hosts
notification_period workhours ; Linux admins hate to be woken up, so we only notify during the day
; Note that the notification_period variable is being overridden from
; the value that is inherited from the generic-host template!
notification_interval 120 ; Resend notifications every 2 hours
notification_options d,u,r ; Only send notifications for specific host states
contact_groups admins ; Notifications get sent to the admins by default
register 0 ; DONT REGISTER THIS DEFINITION - ITS NOT A REAL HOST, JUST A TEMPLATE!
}
# Local service definition template - This is NOT a real service, just a template!
define service{
name local-service ; The name of this service template
use generic-service ; Inherit default values from the generic-service definition
max_check_attempts 4 ; Re-check the service up to 4 times in order to determine its final (hard) state
check_interval 10 ; Check the service every 5 minutes under normal conditions
retry_interval 1 ; Re-check the service every minute until a hard state can be determined
register 0 ; DONT REGISTER THIS DEFINITION - ITS NOT A REAL SERVICE, JUST A TEMPLATE!
notification_interval 60
notification_period 24x7
notification_options c,u,r,w
contact_groups admins
}
Step 3: Create service file in “/usr/local/nagios/etc/servers/” and add below lines in that.
Eg: Monitor Linux host with CPU load, Users, process, disk usage.
define host{
use linux-server
host_name enter-your-host-name
alias enter-your-host-name
address IP-address
hostgroups LinuxServers
}
define service{
use local-service
host_name enter-your-host-name
service_description Root / Partition
check_command check_nrpe!check_disk
}
define service{
use local-service
host_name enter-your-host-name
service_description /mnt Partition
check_command check_nrpe!check_mnt_disk
}
define service{
use local-service
host_name enter-your-host-name
service_description Current Users
check_command check_nrpe!check_users
}
define service{
use local-service
host_name enter-your-host-name
service_description Total Processes
check_command check_nrpe!check_total_procs
}
define service{
use local-service
host_name enter-your-host-name
service_description Current Load
check_command check_nrpe!check_load
}
NRPE Command definition needs to add in “command.cfg” file
vi /usr/local/nagios/etc/objects/command.cfg
# .check_nrpe. command definition
define command{
command_name check_nrpe
command_line /usr/lib64/nagios/plugins/check_nrpe -H $HOSTADDRESS$ -t 30 -c $ARG1$
}
Now test/verify Nagios configuration file for any errors in Nagios Server:
/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg Total Warnings: 0 Total Errors: 0
Now reload your Nagios configuration.
Commands to restart or reload Nagios service
service nagios reload Or service nagios restart
From all these steps you have added a remote Linux host in the Nagios monitoring server. Now goto Nagios monitoring web interface at http://<ipaddress>/nagios and provide username and password and check now the Linux host added, and it is monitoring in Nagios Monitoring Server. This is how to add a Linux host to Nagios monitoring server using nrpe plugin.
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