Nagios Support Forum

Hey all, I'm trying to get NRPE working on one of my servers and I'm not having much luck. In my spelunking I've discovered that I did a package install quite a while ago (that I had forgotten about) and a source install in the last month. AND, in my source install I followed the instructions on http://nagios.sourceforge.net/docs/nrpe/NRPE.pdf and installed xinetd.d which is NOT installed on another server that IS working with NRPE. Within xinetd.d there's a file named nrpe. Here are the contents of that file:

# default: on
# description: NRPE (Nagios Remote Plugin Executor)
service nrpe
{
flags = REUSE
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
log_on_failure += USERID
disable = no
only_from = 192.168.2.26
}

I tried running the "server" "server_args" command/parameter from the command line and nothing happens. Running ps -ef | grep nrpe shows no nrpe service running. If I run the following command from the command line the nrpe service runs:

root@srv-Backup:/etc/init.d# /usr/sbin/nrpe -c /etc/nagios/nrpe.cfg -d
root@srv-Backup:/etc/init.d# ps -ef | grep nrpe
nagios 3250 1 0 09:40 ? 00:00:00 /usr/sbin/nrpe -c /etc/nagios/nrpe.cfg -d
root 3257 1529 0 09:41 pts/0 00:00:00 grep nrpe

I tried putting that command string in the xinetd.d file but nrpe just will not start from the file. Any ideas? I was going to apt-get remove the first nrpe package but would that clean things up enough or should I remove the package install too. OR, have I torpedoed myself?

Thanks,

Joe B

You should start by trying to remove the package with apt and then follow the manual install instructions again, starting with step iv from that document.This is definitely a mistake you can recover from.

And to confirm, should I also install xinetd? As I mentioned in my original post I have another server that doesn't have xinetd installed and it's working.

Thanks,

Joe B

I believe it can be set up with or without xinetd. Do it however the doc says unless you know how to set it up otherwise.

No joy. I've tried it by using the xinetd method but running service xinetd start doesn't do anything (rebooting the server has the same result). I don't even see the command run. Running it without xinetd by using the command /usr/local/nagios/bin/nrpe -c /etc/nagios/nrpe.cfg -d DOES put nrpe up where my Nagios server can see it:

root@srv-Backup:/usr/local/nagios/etc# netstat -at | grep nrpe
tcp 0 0 *:nrpe *:* LISTEN

But Nagios can't understand what this server is saying:

NRPE: Unable to read output

Here's the .cfg half of the statement in xinetd:

-c /usr/local/nagios/etc/nrpe.cfg --inetd

Using this half in the manual command doesn't do anything.

Thanks,

Joe B

jbruyet wrote:NRPE: Unable to read output

This can indicate a problem with the plugin, rather than with NRPE per se. There may be a permission issue somewhere. Try testing your plugins as the nagios user:

Hi agriffin, here's what I'm seeing:

[root@link libexec]# su nagios -s /bin/bash -c "/usr/local/nagios/libexec/check_nrpe -H localhost"
Connection refused by host
[root@link libexec]#

Since I'm getting the "Connection refused by host" error message I think you're correct regarding a possible permission issue somewhere. I went through and installed the Nagios plugins and nrpe again thinking THAT would fix it but no joy. Check out what happens when I run these three commands from the Nagios server:

[root@link libexec]# ./check_nrpe -H 192.168.2.83
NRPE v2.13
[root@link libexec]# ./check_nrpe -H 192.168.2.83 -c check_users
NRPE: Unable to read output
[root@link libexec]# ./check_nrpe -H 192.168.2.83 -c check_cpu
NRPE: Command 'check_cpu' not defined
[root@link libexec]#

Any idea on what permission is wrong and where it might be?

Thanks,

Joe B

Can you post your nrpe.cfg file from the remote machine? After seeing your new error messages, it now seems like the issue is some kind of misconfiguration, either in addition to or instead of a permission problem.

Hi agriffin, here is the contents of my nrpe.cfg file:

#############################################################################
# Sample NRPE Config File
# Written by: Ethan Galstad ([email protected])
#
# Last Modified: 11-23-2007
#
# NOTES:
# This is a sample configuration file for the NRPE daemon. It needs to be
# located on the remote host that is running the NRPE daemon, not the host
# from which the check_nrpe client is being executed.
#############################################################################


# LOG FACILITY
# The syslog facility that should be used for logging purposes.

log_facility=daemon



# PID FILE
# The name of the file in which the NRPE daemon should write it's process ID
# number. The file is only written if the NRPE daemon is started by the root
# user and is running in standalone mode.

pid_file=/var/run/nrpe.pid



# PORT NUMBER
# Port number we should wait for connections on.
# NOTE: This must be a non-priviledged port (i.e. > 1024).
# NOTE: This option is ignored if NRPE is running under either inetd or xinetd

server_port=5666



# SERVER ADDRESS
# Address that nrpe should bind to in case there are more than one interface
# and you do not want nrpe to bind on all interfaces.
# NOTE: This option is ignored if NRPE is running under either inetd or xinetd

#server_address=127.0.0.1



# NRPE USER
# This determines the effective user that the NRPE daemon should run as.
# You can either supply a username or a UID.
#
# NOTE: This option is ignored if NRPE is running under either inetd or xinetd

nrpe_user=nagios



# NRPE GROUP
# This determines the effective group that the NRPE daemon should run as.
# You can either supply a group name or a GID.
#
# NOTE: This option is ignored if NRPE is running under either inetd or xinetd

nrpe_group=nagios



# ALLOWED HOST ADDRESSES
# This is an optional comma-delimited list of IP address or hostnames
# that are allowed to talk to the NRPE daemon. Network addresses with a bit mask
# (i.e. 192.168.1.0/24) are also supported. Hostname wildcards are not currently
# supported.
#
# Note: The daemon only does rudimentary checking of the client's IP
# address. I would highly recommend adding entries in your /etc/hosts.allow
# file to allow only the specified host to connect to the port
# you are running this daemon on.
#
# NOTE: This option is ignored if NRPE is running under either inetd or xinetd

allowed_hosts=127.0.0.1 192.168.2.26



# COMMAND ARGUMENT PROCESSING
# This option determines whether or not the NRPE daemon will allow clients
# to specify arguments to commands that are executed. This option only works
# if the daemon was configured with the --enable-command-args configure script
# option.
#
# *** ENABLING THIS OPTION IS A SECURITY RISK! ***
# Read the SECURITY file for information on some of the security implications
# of enabling this variable.
#
# Values: 0=do not allow arguments, 1=allow command arguments

dont_blame_nrpe=0



# COMMAND PREFIX
# This option allows you to prefix all commands with a user-defined string.
# A space is automatically added between the specified prefix string and the
# command line from the command definition.
#
# *** THIS EXAMPLE MAY POSE A POTENTIAL SECURITY RISK, SO USE WITH CAUTION! ***
# Usage scenario:
# Execute restricted commmands using sudo. For this to work, you need to add
# the nagios user to your /etc/sudoers. An example entry for alllowing
# execution of the plugins from might be:
#
# nagios ALL=(ALL) NOPASSWD: /usr/lib/nagios/plugins/
#
# This lets the nagios user run all commands in that directory (and only them)
# without asking for a password. If you do this, make sure you don't give
# random users write access to that directory or its contents!

# command_prefix=/usr/bin/sudo



# DEBUGGING OPTION
# This option determines whether or not debugging messages are logged to the
# syslog facility.
# Values: 0=debugging off, 1=debugging on

debug=0



# COMMAND TIMEOUT
# This specifies the maximum number of seconds that the NRPE daemon will
# allow plugins to finish executing before killing them off.

command_timeout=60



# CONNECTION TIMEOUT
# This specifies the maximum number of seconds that the NRPE daemon will
# wait for a connection to be established before exiting. This is sometimes
# seen where a network problem stops the SSL being established even though
# all network sessions are connected. This causes the nrpe daemons to
# accumulate, eating system resources. Do not set this too low.

connection_timeout=300



# WEEK RANDOM SEED OPTION
# This directive allows you to use SSL even if your system does not have
# a /dev/random or /dev/urandom (on purpose or because the necessary patches
# were not applied). The random number generator will be seeded from a file
# which is either a file pointed to by the environment valiable $RANDFILE
# or $HOME/.rnd. If neither exists, the pseudo random number generator will
# be initialized and a warning will be issued.
# Values: 0=only seed from /dev/random, 1=also seed from weak randomness

#allow_weak_random_seed=1



# INCLUDE CONFIG FILE
# This directive allows you to include definitions from an external config file.

#include=<somefile.cfg>



# INCLUDE CONFIG DIRECTORY
# This directive allows you to include definitions from config files (with a
# .cfg extension) in one or more directories (with recursion).

#include_dir=<somedirectory>
#include_dir=<someotherdirectory>



# COMMAND DEFINITIONS
# Command definitions that this daemon will run. Definitions
# are in the following format:
#
# command[<command_name>]=<command_line>
#
# When the daemon receives a request to return the results of <command_name>
# it will execute the command specified by the <command_line> argument.
#
# Unlike Nagios, the command line cannot contain macros - it must be
# typed exactly as it should be executed.
#
# Note: Any plugins that are used in the command lines must reside
# on the machine that this daemon is running on! The examples below
# assume that you have plugins installed in a /usr/local/nagios/libexec
# directory. Also note that you will have to modify the definitions below
# to match the argument format the plugins expect. Remember, these are
# examples only!


# The following examples use hardcoded command arguments...

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


# The following examples allow user-supplied arguments and can
# only be used if the NRPE daemon was compiled with support for
# command arguments *AND* the dont_blame_nrpe directive in this
# config file is set to '1'. This poses a potential security risk, so
# make sure you read the SECURITY file before doing this.

#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 $ARG3$

Try changing:
to Hope this helps.