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](https://assets.nagios.com/downloads/nagioscore/docs/Installing_Nagios_Core_From_Source.pdf#_ga=2.210947287.396962911.1500126138-104828703.1500126138)When installing nagios on an ubuntu 17.04 server i had to cp /usr/lib/nagios/plugins/check\_nrpe /usr/local/nagios/libexec/check\_nrpe and apt-get install nagios-nrpe-plugin
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. **On Ubuntu:** ``` apt-get install nagios-nrpe-server nagios-plugins-basic ``` **For CentOS:** 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 On Ubuntu: ``` systemctl enable nagios-nrpe-server systemctl restart nagios-nrpe-server ``` On Centos: ``` systemctl enable nrpe systemctl restart nrpe ``` **Check in CLI** ```shell /usr/local/nagios/libexec/check_nrpe -n -H 10.1.1.1 ``` Or on older versions ```shell /usr/lib/nagios/plugins/check_nrpe ``` ##### **Other NRPE commands:** > command\[check\_ping\]=/usr/local/nagios/libexec/check\_ping 8.8.8.8 -w 50,50% -c 100,90% > command\[check\_vda\]=/usr/lib64/nagios/plugins/check\_disk -w 20% -c 10% -p /dev/vda1 > command\[check\_swap\]=/usr/local/nagios/libexec/check\_swap -w 10% -c 5% > command\[check\_raid\]=/usr/local/nagios/libexec/check\_raid ##### **tcp\_check** > define service{ > use generic-service > host\_name media-server > service\_description Check Emby > check\_command check\_tcp!8096 > }