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Nagios NRPE

 

Downloading Nagios Core:

https://www.nagios.org/downloads/nagios-core/thanks/?t=1500128149

Installing Nagios Core:

Installation is really easy just follow the guide:

https://assets.nagios.com/downloads/nagioscore/docs/Installing_Nagios_Core_From_Source.pdf#_ga=2.210947287.396962911.1500126138-104828703.1500126138

Once it's installed, create a host and a service and the commands.

Lets start by making sure nagios sees the files we are going to create for our hosts and services.

vi /usr/local/nagios/etc/nagios.cfg
cfg_file=/usr/local/nagios/etc/servers/hosts.cfg
cfg_file=/usr/local/nagios/etc/servers/services.cfg
mkdir /usr/local/nagios/etc/servers/

We will start by creating a template we can use for our hosts, then below we will create the host and then create the services for that host.

vim /usr/local/nagios/etc/servers/hosts.cfg
define host{
name                            linux-box               ; 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 ; Inherit default values from a template host_name linux-server-01 ; The name we're giving to this server alias Linux Server 01 ; A longer name for the server address 192.168.1.100 ; IP address of Remote Linux host }
vim /usr/local/nagios/etc/servers/services.cfg
define service{
use                     generic-service
host_name               linux-server-01
service_description     CPU Load
check_command           check_nrpe!check_load
}
vi /usr/local/nagios/etc/objects/commands.cfg

The -H will be for the host it will connect to (192.168.1.100) defined in the host.cfg, the -c will be the name specified on the remote host inside the /etc/nrpe.cfg

define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}

Verify nagios config for errors before restarting.

/usr/local/nagios/bin/nagios -v /usr/local/nagios/etc/nagios.cfg

Restart the service

service nagios restart
Remote host:

now lets install the NRPE plugins and add a few plugins to the config file.

To view the list of plugins you can install:

yum --enablerepo=epel -y list nagios-plugins*
yum install nrpe nagios-plugins-dns nagios-plugins-load nagios-plugins-swap nagios-plugins-disk nagios-plugins-procs

Now we need to add the nagios server (192.168.1.101) and the commands it can execute

vim /etc/nagios/nrpe.cfg
command[check_load]=/usr/local/nagios/libexec/check_load -w 15,10,5 -c 30,25,20

allowed_hosts=127.0.0.1,192.168.1.101

systemctl enable nrpe
systemctl restart nrpe

Now go back to the nagios server and check if it connects.

check_nrpe -H 192.168.1.100

Other NRPE commands:

command[check_ping]=/usr/local/nagios/libexec/check_ping 8.8.8.8 -w 50,50% -c 100,90%
command[check_diskusage]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /dev/disk/by-uuid/[DISK UUID]
command[check_swap]=/usr/local/nagios/libexec/check_swap -w 10% -c 5%
command[check_raid]=/usr/local/nagios/libexec/check_raid