Chapter 3. Installing Nagios Remote Plug-in Executor (NRPE)

NRPE requires OpenSSL. Install the following libraries first.

Execute the following:

[user@host]# yum install openssl openssl-devel gcc make git

[user@host]# apt install openssl libssl-dev gcc make git

NRPE installation requires a Nagios user. So create the user first.

[user@mon]# useradd nagios
[user@mon]# passwd nagios

Download the latest version of the Nagios plug-ins. Then, make and install them.

[user@mon]# wget http://www.nagios-plugins.org/download/nagios-plugins-2.2.1.tar.gz
[user@mon]# tar zxf nagios-plugins-2.2.1.tar.gz
[user@mon]# cd nagios-plugins-2.2.1
[user@mon]# ./configure
[user@mon]# make
[user@mon]# make install

Download the latest verion of the Ceph plug-ins. See https://github.com/valerytschopp/ceph-nagios-plugins for details.

[user@mon]# cd ~
[user@mon]# git clone --recursive https://github.com/valerytschopp/ceph-nagios-plugins.git
[user@mon]# cd ceph-nagios-plugins
[user@mon]# make dist
[user@mon]# make install

NRPE uses xinetd for communication. Install it before installing the NRPE module. Execute the following:

[user@mon]# yum install xinetd

[user@mon]# apt install xinetd

[user@mon]# cd ~
[user@mon]# wget https://github.com/NagiosEnterprises/nrpe/releases/download/nrpe-3.1.0/nrpe-3.1.0.tar.gz
[user@mon]# tar xvfz nrpe-3.1.0.tar.gz
[user@mon]# cd nrpe-3.1.0
[user@mon]# ./configure
[user@mon]# make all
[user@mon]# make install-groups-users
[user@mon]# make install
[user@mon]# make install-config
[user@mon]# make install-init

Then, add nrpe 5666/tcp to the /etc/services file.

[user@mon]# systemctl enable xinetd
[user@mon]# systemctl restart xinetd
[user@mon]# systemctl reload xinetd

[user@mon]# systemctl enable nrpe
[user@mon]# systemctl start nrpe

Open port 5666 to allow communication with NRPE.

[user@mon]# firewall-cmd --zone=public --add-port=5666/tcp
[user@mon]# firewall-cmd --zone=public --add-port=5666/tcp --permanent

[user@mon]# iptables -A INPUT -p tcp --dport 5666 -j ACCEPT
[user@mon]# apt-get install iptables-persistent

In order for the Nagios Core server to access NRPE on a remote machine, the remote machine’s xinetd and NRPE configurations must be updated with the IP address of the Nagios Core server.

Edit the xinetd configuration with the Nagios server’s IP address.

[user@mon]# vim /etc/xinetd.d/nrpe

# default: off
# description: NRPE (Nagios Remote Plugin Executor)
service nrpe
{
    disable         = yes
    socket_type     = stream
    port            = 5666
    wait            = no
    user            = nagios
    group           = nagios
    server          = /usr/local/nagios/bin/nrpe
    server_args     = -c /usr/local/nagios/etc/nrpe.cfg --inetd
    only_from       = 127.0.0.1,<ip-address-of-nagios-core>
    log_on_success  =
}

Add the IP address of the Nagios Core server to the only_from setting. Then, restart xinetd.

[user@mon]# systemctl restart xinetd

Edit the NRPE configuration with the Nagios server’s IP address.

[user@mon]# vim /usr/local/nagios/etc/nrpe.cfg

allowed_hosts=127.0.0.1,<ip-address-of-nagios-core>

Add the IP address of the Nagios Core server to the allowed_hosts setting. Then, restart nrpe.

[user@mon]# systemctl restart nrpe

Ensure that the make and install procedures worked.

[user@host]# /usr/local/nagios/libexec/check_nrpe -H localhost

The check should echo NRPE v3.1.0-rc1 if it is working correctly.