# nagios NRPE: Unable to read output

I currently set up a script to restart my http servers + php5 fpm but can't get it to work. I have googled and have found that mostly permissions are the problems of my error but can't figure it out.

I start my script using

/usr/lib/nagios/plugins/check_nrpe -H bart -c restart_http


This is the output in my syslog on the node I want to restart

 Jun 27 06:29:35 bart nrpe[8926]: Connection from 192.168.133.17 port 25028
Jun 27 06:29:35 bart nrpe[8926]: Host address is in allowed_hosts
Jun 27 06:29:35 bart nrpe[8926]: Handling the connection...
Jun 27 06:29:35 bart nrpe[8926]: Host is asking for command 'restart_http' to be run...
Jun 27 06:29:35 bart nrpe[8926]: Running command: /usr/bin/sudo /usr/lib/nagios/plugins/http-restart
Jun 27 06:29:35 bart nrpe[8926]: Command completed with return code 1 and output:
Jun 27 06:29:35 bart nrpe[8926]: Return Code: 1, Output: NRPE: Unable to read output
Jun 27 06:29:35 bart nrpe[8926]: Connection from 192.168.133.17 closed.


If I run the command myself it runs fine (but asks for a password) (nagios user)

This are the script permission and the script contents.

-rwxrwxrwx 1 nagios nagios 142 Jun 26 21:41 /usr/lib/nagios/plugins/http-restart

#!/bin/bash
echo "ok"
/etc/init.d/nginx stop
/etc/init.d/nginx start
/etc/init.d/php5-fpm stop
/etc/init.d/php5-fpm start
echo "done"


I also added this line to visudo

nagios ALL=(ALL) NOPASSWD: /usr/lib/nagios/plugins/

My local nagios nrpe.cfg

#############################################################################
# Sample NRPE Config File
# Written by: Ethan Galstad (nagios@nagios.org)
#
#
# 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/nagios/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

# 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

# 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.
#
# 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=127.0.0.1,192.168.133.17

# 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=1

# 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/[u]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/lib/nagios/plugins/check_users -w 5 -c 10
command[check_hda1]=/usr/lib/nagios/plugins/check_disk -w 20% -c 10% -p /dev/hda1
command[check_zombie_procs]=/usr/lib/nagios/plugins/check_procs -w 5 -c 10 -s Z
command[check_total_procs]=/usr/lib/nagios/plugins/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/lib/nagios/plugins/check_users -w $ARG1$ -c $ARG2$
#command[check_load]=/usr/lib/nagios/plugins/check_load -w $ARG1$ -c $ARG2$
#command[check_disk]=/usr/lib/nagios/plugins/check_disk -w $ARG1$ -c $ARG2$ -p $ARG3$
#command[check_procs]=/usr/lib/nagios/plugins/check_procs -w $ARG1$ -c $ARG2$ -s $ARG3$
command[restart_http]=/usr/lib/nagios/plugins/http-restart

#
# local configuration:
#   if you'd prefer, you can instead place directives here
include=/etc/nagios/nrpe_local.cfg

#
# you can place your config snipplets into nrpe.d/
include_dir=/etc/nagios/nrpe.d/


My Sudoers files

# /etc/sudoers
#
# This file MUST be edited with the 'visudo' command as root.
#
# See the man page for details on how to write a sudoers file.
#

Defaults    env_reset

# Host alias specification

# User alias specification

# Cmnd alias specification

# User privilege specification
root    ALL=(ALL) ALL
nagios  ALL=(ALL) NOPASSWD: /usr/lib/nagios/plugins/

# Allow members of group sudo to execute any command
# (Note that later entries override this, so you might need to move
# it further down)
%sudo ALL=(ALL) ALL
#
#includedir /etc/sudoers.d


Hopefully someone can help!

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Never chmod 777 for a shell script, 755 is enough. What is the output of su - nagios -c 'sudo /usr/lib/nagios/plugins/http-restart'? –  quanta Jun 27 '12 at 5:18
@quanta su - nagios -c 'sudo /usr/lib/nagios/plugins/http-restart' Password: ok Stopping nginx: nginx. Starting nginx: nginx. done => It executes fine but I need to give my passwd –  wloockx Jun 27 '12 at 5:21
Post your full /etc/sudoers file? –  quanta Jun 27 '12 at 5:30
@quanta added it to the post. –  wloockx Jun 27 '12 at 5:58
Move the nagios... line to the end of /etc/sudoers file and try again. –  quanta Jun 27 '12 at 6:07

Since I see there is no problem with the line you added to /etc/sudoers file:

nagios  ALL=(ALL) NOPASSWD: /usr/lib/nagios/plugins/


I suspect that there is a later entry in /etc/sudoers that override NOPASSWD option and that is reason for http-restart still asking for a password. With your above config, is nagios user a member of sudo group?

Just try to move this line to the end of /etc/sudoers file to exclude this possibility. Also make sure the nrpe user does not need a tty, by setting Defaults:nrpe !requiretty.

UPDATE Wed Jun 27 21:24:21 ICT 2012

To make the NRPE work, you also need to add sudo to your command definition in nrpe.cfg:

command[restart_http]=/usr/bin/sudo /usr/lib/nagios/plugins/http-restart

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Be aware of the fact that if you pass argument to NRPE, the Dont_blame option need to be 1

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