nagios-nrpe/README.md

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