Nagios

Install Server

From: https://help.ubuntu.com/lts/serverguide/nagios.html.en

sudo apt install nagios3 nagios-nrpe-plugin

Install Client

apt-get install nagios-nrpe-server nagios-plugins-basic -y

Client Important Files

/etc/nagios/nrpe.cfg           <- allowed_hosts of server goes here
/usr/lib/nagios/plugins 	<- specific checks go here

Server Important Files

/usr/lib/nagios/plugins		<- nothing important here, actually
/etc/nagios3/config.d                  <- everything goes here

Nagios Config

• make sure IPs, ports, security groups allow communication
• client: in /etc/nagios/nrpe.cfg:

allowed_hosts <should include the server ip>
command[echo_ok3]=/usr/lib/nagios/plugins/echo_ok3

• client: restart service

sudo kill -9 `ps aux | grep nr | grep -v color | awk '{print $2}'` ; /usr/sbin/nrpe -c /etc/nagios/nrpe.cfg -d 

• server:

define command {
  command_name echo-ok3
  command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c echo_ok3
}
define service {
  service_description echo-ok3
  hostgroup_name microsites3_api
  check_command echo-ok3
  use default-service
}

Nagios Utils

Setup Client

apt-get install -y nagios-plugins nagios-nrpe-server

Change password

htpasswd -c -b  /etc/nagios/htpasswd.users nagiosadmin admin

Nagios Custom Plugin

CHECK_NRPE: Error – Could not complete SSL handshake

From: https://geekpeek.net/could-not-complete-ssl-handshake/

Add a new custom check

Implement a new custom check:

• assume nagios3 server is already installed
• install nagios-nrpe-server on the client (sudo apt-get install nagios-nrpe-server -y)
• make sure allowed hosts are correct, as per https://geekpeek.net/could-not-complete-ssl-handshake/ (/etc/nagios/nrpe.conf)
• create the entry for the command on client in /etc/nagios/nrpe.conf (command[check_mongod]=/usr/lib/nagios/plugins/check_mongod)
• create /usr/lib/nagios/plugins/check_mongod
• restart nagios-nrpe-server
• check that you can connect on the server: ( root@utils:/usr/lib/nagios/plugins# ./check_nrpe -H 10.138.224.158 -c check_mongod )
• add this check to this host

root@utils:/etc/nagios3/conf.d# cat dev_mongo2.cfg | grep mongod -B 3 -A 7
define service{
  use generic-service
  host_name dev-mongo2.operaevent
  service_description mongod service
  check_command check_mongod
  }

• restart server ( root@utils:/etc/nagios3/conf.d# sudo service nagios3 restart )

Notes

https://geekpeek.net/could-not-complete-ssl-handshake/

verify configuration:

nagios3 -v /etc/nagios3/nagios.cfg

on client:

sudo service nagios-nrpe-server  restart

on server:

sudo service nagios3 restart