NRPE README

For installation instructions and information on the design overview of the NRPE addon, please read the PDF documentation that is found in this directory: docs/NRPE.pdf

If you are upgrading from a previous version, run 'update-cfg.pl' to add the new SSL parameters to your config file.

Purpose

The purpose of this addon is to allow you to execute Nagios plugins on a remote host in as transparent a manner as possible.

Contents

There are two pieces to this addon:

1. NRPE - This program runs as a background process on the remote host and processes command execution requests from the check_nrpe plugin on the Nagios host. Upon receiving a plugin request from an authorized host, it will execute the command line associated with the command name it received and send the program output and return code back to the check_nrpe plugin

2. check_nrpe - This is a plugin that is run on the Nagios host and is used to contact the NRPE process on remote hosts. The plugin requests that a plugin be executed on the remote host and wait for the NRPE process to execute the plugin and return the result. The plugin then uses the output and return code from the plugin execution on the remote host for its own output and return code.

Compiling

The code is very basic and may not work on your particular system without some tweaking. If you are having any problems compiling on your system, please let us know, hopefully with fixes. Most users should be able to compile NRPE and the check_nrpe plugin with the following commands...

./configure
make all

The binaries will be located in the src/ directory after you run make all and will have to be installed manually somewhere on your system.

NOTE: Since the check_nrpe plugin and nrpe daemon run on different machines (the plugin runs on the Nagios host and the daemon runs on the remote host), you will have to compile the nrpe daemon on the target machine.

Installing

The check_nrpe plugin should be placed on the Nagios host along with your other plugins. In most cases, this will be in the /usr/local/nagios/libexec directory.

The nrpe program and the configuration file nrpe.cfg should be placed somewhere on the remote host. Note that you will also have to install some plugins on the remote host if you want to make much use of this addon.

Configuring

Sample config files for the NRPE daemon are located in the sample-config/ subdirectory.

Running Under INETD or XINETD

If you plan on running nrpe under inetd or xinetd and making use of TCP wrappers, you need to add a line to your /etc/services file as follows (modify the port number as you see fit)

 nrpe            5666/tcp    # NRPE

The run make install-inetd to copy the appropriate file, or add the appropriate line to your /etc/inetd.conf.

NOTE: If you run nrpe under inetd or xinetd, the server_port and allowed_hosts variables in the nrpe configuration file are ignored.

INETD

After running make install-inetd, your /etc/inetd.conf file will contain lines similar to the following:

	#
	# Enable the following entry to enable the nrpe daemon
	#nrpe stream tcp nowait nagios /usr/local/nagios/bin/nrpe nrpe -c /usr/local/nagios/etc/nr
	# Enable the following entry if the nrpe daemon didn't link with libwrap
	#nrpe stream tcp nowait nagios /usr/sbin/tcpd /usr/local/nagios/bin/nrpe -c /usr/local/nag

Un-comment the appropriate line, then Restart inetd:

/etc/rc.d/init.d/inet restart

OpenBSD users can use the following command to restart inetd:

kill -HUP `cat /var/run/inet.pid`

Then add entries to your /etc/hosts.allow and /etc/hosts.deny file to enable TCP wrapper protection for the nrpe service. This is optional, although highly recommended.

XINETD

If your system uses xinetd instead of inetd, make install-inetd will create a file called nrpe in your /etc/xinetd.d directory that contains a file similar to this:

    # default: off
    # description: NRPE (Nagios Remote Plugin Executor)
    service nrpe
    {
        disable         = yes
        socket_type     = stream
        port            = @NRPE_PORT@
        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
        log_on_failure  += USERID
    }

• Replace disable = yes with disable = no
• Replace the 127.0.0.1 field with the IP addresses of hosts which are allowed to connect to the NRPE daemon. This only works if xinetd was compiled with support for tcpwrappers.
• Add entries to your /etc/hosts.allow and /etc/hosts.deny file to enable TCP wrapper protection for the nrpe service. This is optional, although highly recommended.

Restart xinetd:

/etc/rc.d/init.d/xinetd restart

Configuring Things On The Nagios Host

Examples for configuring the nrpe daemon are found in the sample nrpe.cfg file included in this distribution. That config file resides on the remote host(s) along with the nrpe daemon. The check_nrpe plugin gets installed on the Nagios host. In order to use the check_nrpe plugin from within Nagios, you will have to define a few things in the host config file. An example command definition for the check_nrpe plugin would look like this:

define command{
    command_name    check_nrpe
    command_line    /usr/local/nagios/libexec/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
    }

In any service definitions that use the nrpe plugin/daemon to get their results, you would set the service check command portion of the definition to something like this (sample service definition is simplified for this example):

define service{
    host_name           someremotehost
    service_description someremoteservice
    check_command       check_nrpe!yourcommand
    ... etc ...
    }

where yourcommand is a name of a command that you define in your nrpe.cfg file on the remote host (see the docs in the sample nrpe.cfg file for more information).

Questions?

If you have questions about this addon, or problems getting things working, first try searching the nagios-users mailing list archives. Details on searching the list archives can be found at http://www.nagios.org

If you don't find an answer there, post a message in the Nagios Plugin Development forum at https://support.nagios.com/forum/viewforum.php?f=35