Before the installation we have a look at the design chart of the nrpe:
The NRPE addon consists of two pieces:
• The check_nrpe plugin, which resides on the local monitoring Host
• The NRPE daemon, which runs on the remote Linux/Unix machine
When Nagios needs to monitor a resource of service from a remote Linux/Unix machine:
• Nagios will execute the check_nrpe plugin and tell it what service needs to be checked
• The check_nrpe plugin contacts the NRPE daemon on the remote host over an (optionally) SSL protected connection
• The NRPE daemon runs the appropriate Nagios plugin to check the service or resource
• The results from the service check are passed from the NRPE daemon back to the check_nrpe plugin, which then returns the check results to the Nagios process.
Linux Client
You can install the plugin on a Linux server that will be monitored. In addition, you also need to plugin executor NRPE.
On Remote machine
1. Library installation and Account Setup:
yum install openssl openssl-devel gcc xinetd
useradd nagios
2. Install Nagios Plugins:
Download the latest nagios-plugins-x.x.x.tar.gz : http://nagios-plugins.org/download/
# tar xzf nagios-plugins-2.1.1.tar.gz # cd nagios-plugins-2.1.1
# gunzip -c nagios-plugins-2.1.1.tar.gz | tar xf -
# ./configure # make # make install
# chown nagios.nagios /usr/local/nagios # chown -R nagios.nagios /usr/local/nagios/libexec
3. Install NRPE (Nagios Remote plugin executor)
Manually:
Download Load NRPE : https://exchange.nagios.org/directory/Addons/Monitoring-Agents/NRPE–2D-Nagios-Remote-Plugin-Executor/details
tar -xvf nrpe-3.0.1.tar.gz
./configure
make all
make install-daemon
make install-init
In /etc/services add entry:
nrpe 5666/tcp #NRPE Nagios Client
Copy nrpe.xinetd from nrpe samplefiles to /etc/xinetd.d
Configure /etc/xinetd.d/nrpe.xinetd
change the only_from =xxx.xxx.xxx.xx to the IP of the nagios monitor server.
Restart xinetd:
service xinetd restart
mkdir /usr/local/nagios/etc/
Copy the nrpe.cfg from the sample-conf to /usr/local/nagios/etc/nrpe.cfg
Then configure:
allowed_hosts=127.0.0.1, xxx.xxx.xxx.xxxmak
xxx.xxx.xxx.xxx is the nagios monitoring server’s IP address.
dont_blame_nrpe=1
common out these lines (around lines 287) to disable the hard-coded command:
#command[check_users]=/usr/local/nagios/libexec/check_users -w 5 -c 10 #command[check_load]=/usr/local/nagios/libexec/check_load -w 15,10,5 -c 30,25,20 #command[check_hda1]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /dev/hda1 #command[check_zombie_procs]=/usr/local/nagios/libexec/check_procs -w 5 -c 10 -s Z #command[check_total_procs]=/usr/local/nagios/libexec/check_procs -w 150 -c 200
Uncommon these lines to allow parameters
command[check_users]=/usr/local/nagios/libexec/check_users -w $ARG1$ -c $ARG2$ command[check_load]=/usr/local/nagios/libexec/check_load -w $ARG1$ -c $ARG2$ command[check_disk]=/usr/local/nagios/libexec/check_disk -w $ARG1$ -c $ARG2$ -p $ARG3$ command[check_procs]=/usr/local/nagios/libexec/check_procs -w $ARG1$ -c $ARG2$ -s $ARG3$
Install from yum(2.15 as of now)
sudo yum install -y nrpe nagios-plugins-{ping,disk,users,procs,load,swap,ssh}
vi /etc/nagios/nrpe.cfg
# line 81: add access permission (specify Nagios server)
allowed_hosts=127.0.0.1,10.0.0.30
# line 97: permit arguments of commands
dont_blame_nrpe=1
# line 210: comment out all
# 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_hda1]=/usr/lib64/nagios/plugins/check_disk -w 20% -c 10% -p /dev/hda1
# command[check_zombie_procs]=/usr/lib64/nagios/plugins/check_procs -w 5 -c 10 -sZ
# command[check_total_procs]=/usr/lib64/nagios/plugins/check_procs -w 150 -c 200
# line 223: uncomment all
command[check_users]=/usr/lib64/nagios/plugins/check_users -w $ARG1$ -c $ARG2$
command[check_load]=/usr/lib64/nagios/plugins/check_load -w $ARG1$ -c $ARG2$
command[check_disk]=/usr/lib64/nagios/plugins/check_disk -w $ARG1$ -c $ARG2$ -p $ARG3$
command[check_procs]=/usr/lib64/nagios/plugins/check_procs -w $ARG1$ -c $ARG2$ -s $ARG3$
[root@node01 ~]# systemctl start nrpe
[root@node01 ~]# systemctl enable nrpe
Firewall settings
On legacy Linux:
Open firewall /etc/sysconfig/iptables
or On centos 7
firewall-cmd --zone=public --add-port=5666/tcp --permanenton Nagios Server
Make sure you have plugin check_nrpe in /usr/local/nagios/libexec, if not install it by the steps: https://support.nagios.com/kb/article.php?id=569
Copy template
cp /usr/local/nagios/etc/objects/localhost.cfg /usr/local/nagios/etc/objects/linuxclient.cfg
Configure /usr/local/nagios/etc/nagios.cfg
Add the new configured template ” linuxclient.cfg” to the nagios.cfg:
cfg_file=/usr/local/nagios/etc/objects/linuxclient.cfg
Modify the linuxclient.cfg file:
1. Replace the localhost with linuxclient: 1,$ s/localhost/linuxclient/g
2. Configure the resources we need to monitor:
Note that the original one is using check_local_disk, check_local_procs, etc, you need to change to check_nrpe!check_disk
Create a command definition
Before that, You’ll need to create a command definition in one of your Nagios object configuration files in order to use the check_nrpe plugin. Open the sample commands.cfg file for editing…
# vimacs /usr/local/nagios/etc/commands.cfg
and add the following definition to the file:
define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}
Configure the host file
You are now ready to start adding services that should be monitored on the remote machine to the Nagios configuration
# create new
define host{
use linux-server
host_name linuxclient
alias linuxclient
address 192.168.90.29
}
define service{
use generic-service
host_name linuxclient
service_description PING
check_command check_ping!100.0,20%!500.0,60%
}
# for free disk
define service{
use generic-service
host_name linuxclient
service_description Root Partition
check_command check_nrpe!check_disk\!20%\!10%\!/
}
# for current users
define service{
use generic-service
host_name linuxclient
service_description Current Users
check_command check_nrpe!check_users\!20\!50
}
# for total processes
define service{
use generic-service
host_name linuxclient
service_description Total Processes
check_command check_nrpe!check_procs\!250\!400\!RSZDT
}
# for current load
define service{
use generic-service
host_name linuxclient
service_description Current Load
check_command check_nrpe!check_load\!5.0,4.0,3.0\!10.0,6.0,4.0
}
Restart nagios:
service nagios restart
Add New command on the remote Linux Host:
If you want to check other disk space by new command, such as root / :
On the Remote machine:
Open the file: /usr/local/nagios/etc/nrpe.cfg
Add following line
command[check_root]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /
reload the nrpe service:
sudo service nrpe restart
On the monitoring machine:
Then ran this command on the monitoring nagios server after editing nrpe.cfg on remote machine:
/usr/local/nagios/libexec/check_nrpe -H ('linux1' ip address of linux host to monitor) -c check_root
On my remote host configuration file /usr/local/nagios/etc/object/linux.cfg, add command:
check_command check_nrpe!check_root
Reload the nagios service:
sudo service nagios restart