NRPE README

** UPDATED DOCUMENTATION!

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

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. I just haven't put a lot of effort into this addond. Most Linux 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 do the following things:

1) Add a line to your /etc/services file as follows (modify the port number as you see fit)

nrpe            5666/tcp    # NRPE

2) Add entries for the NRPE daemon to either your inetd or xinetd configuration files. Which one your use will depend on which superserver is installed on your system. Both methods are described below. NOTE: If you run nrpe under inetd or xinetd, the server_port and allowed_hosts variables in the nrpe configuration file are ignored.

INETD If your system uses the inetd superserver WITH tcpwrappers, add an entry to /etc/inetd.conf as follows:

nrpe    stream  tcp     nowait  <user> /usr/sbin/tcpd <nrpebin> -c <nrpecfg> --inetd

If your system uses the inetd superserver WITHOUT tcpwrappers, add an entry to /etc/inetd.conf as follows:

nrpe    stream  tcp     nowait  <user> <nrpebin> -c <nrpecfg> --inetd

• Replace with the name of the user that the nrpe server should run as. Example: nagios

• Replace with the path to the nrpe binary on your system. Example: /usr/local/nagios/nrpe

• Replace with the path to the nrpe config file on your system. Example: /usr/local/nagios/nrpe.cfg

  XINETD If your system uses xinetd instead of inetd, you'll probably want to create a file called 'nrpe' in your /etc/xinetd.d directory that contains the following entries:

  default: on

  description: NRPE

  service nrpe { flags = REUSE socket_type = stream
  wait = no user = server = server_args = -c --inetd log_on_failure += USERID disable = no only_from = ... }

• Replace with the name of the user that the nrpe server should run as.

• Replace with the path to the nrpe binary on your system.

• Replace with the path to the nrpe config file on your system.

• Replace the fields 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.

3) Restart inetd or xinetd will the following command (pick the on that is appropriate for your system:

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

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

OpenBSD users can use the following command to restart inetd:

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

4) 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.

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'll 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 all else fails, you can email me and I'll try and respond as soon as I get a chance.

-- Ethan Galstad ([email protected])