CHECK_NRPE: Error - Could not connect to . Check system logs

[npolovenko]

Also, on the Solaris server please run this command and show me the output:

ls -l /usr/local/nagios/libexec/

[anilgupta]

Save the file and restart the nrpe service on the Solaris server one more time.

Executed the action plan as suggested.

Also, on the Solaris server please run this command and show me the output:

Please find below the output

Code: Select all

bash-3.2# uname -a
SunOS csbtipdcapmdw07 5.10 Generic_150400-63 sun4v sparc sun4v
bash-3.2# ls -l /usr/local/nagios/libexec/
total 29690
-rwxr-xr-x   1 wassrv   wassrv       844 Sep  4  2013 check_alertlog
-rwxr-xr-x   1 wassrv   wassrv      1860 May 16  2012 check_app_disk
-rwxr-xr-x   1 wassrv   wassrv    267532 Sep 11  2012 check_apt
-rwxr-xr-x   1 wassrv   wassrv      2245 Sep 11  2012 check_breeze
-rwxr-xr-x   1 wassrv   wassrv    113688 Sep 11  2012 check_by_ssh
-rwxr-xr-x   1 wassrv   wassrv    167508 Sep 11  2012 check_clamd
-rwxr-xr-x   1 wassrv   wassrv     85956 Sep 11  2012 check_cluster
-rwxr-xr-x   1 wassrv   wassrv    107492 Sep 11  2012 check_dig
-rwxr-xr-x   1 wassrv   wassrv    328424 Sep 11  2012 check_disk
-rwxr-xr-x   1 wassrv   wassrv      9148 Sep 11  2012 check_disk_smb
-rwxr-xr-x   1 wassrv   wassrv    113656 Sep 11  2012 check_dns
-rwxr-xr-x   1 wassrv   wassrv      2670 Oct 20  2015 check_ds
-rwxr-xr-x   1 wassrv   wassrv     65824 Sep 11  2012 check_dummy
-rwxr-xr-x   1 wassrv   wassrv      3056 Sep 11  2012 check_file_age
-rwxr-xr-x   1 wassrv   wassrv      6318 Sep 11  2012 check_flexlm
-rwxr-xr-x   1 wassrv   wassrv    167508 Sep 11  2012 check_ftp
-rwxr-xr-x   1 wassrv   wassrv      1815 May 24  2012 check_gosecadmin
-rwxr-xr-x   1 wassrv   wassrv       797 Nov 13  2012 check_gosecenrol
-rwxr-xr-x   1 wassrv   wassrv       839 Jun 21  2013 check_gosecenrol_log
-rwxr-xr-x   1 wassrv   wassrv    407748 Sep 11  2012 check_http
-rwxr-xr-x   1 wassrv   wassrv      1510 May  6  2012 check_https
-rwxr-xr-x   1 wassrv   wassrv     15137 Sep 11  2012 check_ifoperstatus
-rwxr-xr-x   1 wassrv   wassrv     12601 Sep 11  2012 check_ifstatus
-rwxr-xr-x   1 wassrv   wassrv    167508 Sep 11  2012 check_imap
-rwxr-xr-x   1 wassrv   wassrv      6890 Sep 11  2012 check_ircd
-rwxr-xr-x   1 wassrv   wassrv    167508 Sep 11  2012 check_jabber
-rwxr-xr-x   1 wassrv   wassrv    110804 Sep 11  2012 check_ldap
-rwxr-xr-x   1 wassrv   wassrv    110804 Sep 11  2012 check_ldaps
-rwxr-xr-x   1 wassrv   wassrv      2317 May 14  2013 check_load
-rwxr-xr-x   1 wassrv   wassrv      6320 Apr 30  2013 check_log
-rwxr-xr-x   1 wassrv   wassrv      6014 Nov 19  2012 check_log.orig
-rwxr-xr-x   1 wassrv   wassrv     20287 Sep 11  2012 check_mailq
-rwxr-xr-x   1 wassrv   wassrv     89868 Sep 11  2012 check_mrtg
-rwxr-xr-x   1 wassrv   wassrv     89268 Sep 11  2012 check_mrtgtraf
-rwxr-xr-x   1 wassrv   wassrv     95840 Sep 11  2012 check_nagios
-rwxr-xr-x   1 wassrv   wassrv    167508 Sep 11  2012 check_nntp
-rwxr-xr-x   1 wassrv   wassrv    167508 Sep 11  2012 check_nntps
-rwxrwxr-x   1 wassrv   wassrv     71476 Sep  6  2013 check_nrpe
-rwxr-xr-x   1 wassrv   wassrv    113188 Sep 11  2012 check_nt
-rwxr-xr-x   1 wassrv   wassrv    116256 Sep 11  2012 check_ntp
-rwxr-xr-x   1 wassrv   wassrv    110856 Sep 11  2012 check_ntp_peer
-rwxr-xr-x   1 wassrv   wassrv    108720 Sep 11  2012 check_ntp_time
-rwxr-xr-x   1 wassrv   wassrv    132300 Sep 11  2012 check_nwstat
-rwxr-xr-x   1 wassrv   wassrv      1697 May  6  2012 check_oam
-rwxr-xr-x   1 wassrv   wassrv       820 Jan  8  2013 check_oid_log
-rwxr-xr-x   1 wassrv   wassrv      2079 Oct 20  2015 check_oim
-rwxr-xr-x   1 wassrv   wassrv      1949 Nov 14  2012 check_oimnull
-rwxr-xr-x   1 wassrv   wassrv      1591 Sep 26  2012 check_ora
-rwxr-xr-x   1 wassrv   wassrv      8325 Sep 11  2012 check_oracle
-rwxr-xr-x   1 wassrv   wassrv      1442 May  3  2012 check_ovd
-rwxr-xr-x   1 wassrv   wassrv    102688 Apr 30  2012 check_overcr
-rwxr-xr-x   1 wassrv   wassrv    100200 Sep 11  2012 check_pgsql
-rwxr-xr-x   1 wassrv   wassrv    117912 Sep 11  2012 check_ping
-rwxr-xr-x   1 wassrv   wassrv    167508 Sep 11  2012 check_pop
-rwxr-xr-x   1 wassrv   wassrv    293360 Sep 11  2012 check_procs
-rwxr-xr-x   1 wassrv   wassrv    100104 Sep 11  2012 check_real
-rwxr-xr-x   1 wassrv   wassrv      9584 Sep 11  2012 check_rpc
-rwxr-xr-x   1 wassrv   wassrv      1414 Sep 11  2012 check_sensors
-rwxr-xr-x   1 wassrv   wassrv    167508 Sep 11  2012 check_simap
-rwxr-xr-x   1 wassrv   wassrv    353292 Sep 11  2012 check_smtp
-rwxr-xr-x   1 wassrv   wassrv    167508 Sep 11  2012 check_spop
-rwxr-xr-x   1 wassrv   wassrv     96764 Sep 11  2012 check_ssh
-rwxr-xr-x   1 wassrv   wassrv    167508 Sep 11  2012 check_ssmtp
-rwxr-xr-x   1 wassrv   wassrv    167508 Sep 11  2012 check_tcp
-rwxr-xr-x   1 wassrv   wassrv     99328 Sep 11  2012 check_time
-rwxr-xr-x   1 wassrv   wassrv    167508 Sep 11  2012 check_udp
-rwxr-xr-x   1 wassrv   wassrv    108308 Sep 11  2012 check_ups
-rwxr-xr-x   1 wassrv   wassrv     83308 Sep 11  2012 check_users
-rwxr-xr-x   1 wassrv   wassrv      2939 Sep 11  2012 check_wave
-rwxr-xr-x   1 wassrv   wassrv      1461 May  6  2012 check_weblogic
-rw-r--r--   1 wassrv   wassrv    143872 Sep 11  2012 checks.tar
-rw-r--r--   1 wassrv   wassrv       276 Mar 14  2013 enrolscriptenv
drwxr-xr-x   2 wassrv   wassrv         4 Dec 20  2012 eventhandlers
-rwxr-xr-x   1 wassrv   wassrv     96260 Sep 11  2012 negate
-rw-r--r--   1 wassrv   wassrv       176 May 29  2012 newmail
-rwxr-xr-x   1 wassrv   wassrv      2526 Jun 30  2015 notify.pl
-rwxr-xr-x   1 wassrv   wassrv       504 Jan 25  2013 restart-oid
-rw-r--r--   1 wassrv   wassrv       315 Jan  8  2013 scriptenv
-rw-r--r--   1 wassrv   wassrv   6656000 Sep  6  2013 scripts.tar
-rwxr-xr-x   1 wassrv   wassrv      1563 Apr 30  2013 sendmail
-rw-r--r--   1 wassrv   wassrv       584 Dec 20  2012 setenv
-rwxr-xr-x   1 wassrv   wassrv     92524 Sep 11  2012 urlize
-rwxr-xr-x   1 wassrv   wassrv      1938 Sep 11  2012 utils.pm
-rwxr-xr-x   1 wassrv   wassrv      2728 Oct 17  2013 utils.sh
bash-3.2# 

After the nrpre restart I do not see any change in error message.

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[guptaa@cacbigdcapmdw51 log]$ date;/usr/local/nagios/libexec/check_nrpe -H 10.92.34.66 -t 30 -c check_disk -a '-w 20% -c 10% -p /'
Tue Apr  9 15:43:07 EDT 2019
CHECK_NRPE: Receive header underflow - only 0 bytes received (4 expected).

[anilgupta]

nrpe.cfg file after the change, just for your reference.

Code: Select all

bash-3.2# uname -a
SunOS csbtipdcapmdw07 5.10 Generic_150400-63 sun4v sparc sun4v
bash-3.2# cat nrpe.cfg
#############################################################################
# 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/tmp/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=10.92.34.66



# 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=wassrv



# 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=wassrv



# 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=127.0.0.1,10.92.34.51,10.92.34.49,10.92.34.53,10.92.34.52,cacbigdcapmdw51.mgmt.cihs.gov.on.ca
allowed_hosts=127.0.0.1,10.92.34.51,10.92.34.49,10.92.34.53,10.92.34.52,cacbigdcapmdw51.mgmt.cihs.gov.on.ca, 10.194.78.208, 10.194.78.206
 


# 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/[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/local/nagios/libexec/check_users -w 5 -c 10
command[check_app_disk]=/usr/local/nagios/libexec/check_app_disk -w 80 -c 90
command[check_load]=/usr/local/nagios/libexec/check_load -w 6 -c 10 
command[check_oid_log]=/usr/local/nagios/libexec/check_oid_log
command[check_gosecenrol_log]=/usr/local/nagios/libexec/check_gosecenrol_log
command[check_disk]=/usr/local/nagios/libexec/check_disk $ARG1$
bash-3.2# 

[anilgupta]

@npolovenko,

Could you please suggest alternate way to expedite the troubleshooting?
I work 8:30 AM till 4:30PM EST. I get less time to work on the issue.

The production deployment is waiting on fix of this issue.

Please suggest.

[npolovenko]

@anilgupta, Let's try the following. In the nrpe.cfg file change the check_disk command to look like this:

command[check_disk]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /

Save the file, restart the nrpe agent again and run these commands from the nagios server.

/usr/local/nagios/libexec/check_nrpe -H 10.92.34.66 -t 30 -c check_disk

/usr/local/nagios/libexec/check_nrpe -2 -H 10.92.34.66 -t 30 -c check_disk

And show me the output.

For faster assistance you can escalate this issue to a support ticket:
https://support.nagios.com/tickets/
That way we'll be able to organize a screen sharing session to resolve this.

[anilgupta]

And show me the output.

After making the change, the command is working as expected.

Code: Select all

[guptaa@cacbigdcapmdw51 libexec]$ /usr/local/nagios/libexec/check_nrpe -H 10.92.34.66 -t 30 -c check_disk
DISK OK - free space: / 35654 MB (71% inode=99%);| /=14338MB;39993;44992;0;49992
[guptaa@cacbigdcapmdw51 libexec]$ /usr/local/nagios/libexec/check_nrpe -2 -H 10.92.34.66 -t 30 -c check_disk
DISK OK - free space: / 35654 MB (71% inode=99%);| /=14338MB;39993;44992;0;49992
[guptaa@cacbigdcapmdw51 libexec]$

Additionally, I created command similar to "check_nrpe" with command_line as "

Code: Select all

$USER1$/check_nrpe -H $HOSTADDRESS$ -t 30 -c $ARG1$

". Now this new check_nrpe is working for Check_Disk.

Till here, we are satisfied.

However, we are encountering below issues:
1) I need to monitor CPU on the same server. I did below :
(a) added

Code: Select all

"command[check_cpu_stats]=/usr/local/nagios/libexec/check_cpu_stats -w 70,40,30 -c 90,60,40"

in nrpe.cfg
(b) Restarted nrpe
(c) Below command shows "Unable to read output"

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/usr/local/nagios/libexec/check_nrpe -H 10.92.34.66 -t 30 -c check_cpu_stats       
NRPE: Unable to read output

I don't see CPU related file under

Code: Select all

/usr/local/nagios/libexec/

on target Solaris server. Could that be the reason for this error, please suggest.

2) Host Status is showing down with status information as "CRITICAL - 10.92.34.66: rta nan, lost 100%"

[npolovenko]

@anilgupta

After making the change, the command is working as expected.

Great. I think the previous version of the command didn't work because you have the following option disabled in the nrpe.cfg:

dont_blame_nrpe=0

You should change it to:

dont_blame_nrpe=1

And restart the nrpe agent.

I don't see CPU related file under /usr/local/nagios/libexec/ on target Solaris server. Could that be the reason for this error, please suggest.

Yep, that's the problem. Because all this command does is it points to the plugin installed locally on the solaris server.

command[check_cpu_stats]=/usr/local/nagios/libexec/check_cpu_stats -w 70,40,30 -c 90,60,40

You can download the actual plugin from here:

https://exchange.nagios.org/directory/P ... sh/details

And place it into the /usr/local/nagios/libexec/ folder on the Solaris server. Use WinSCP or FileZilla to upload files.
After that you should give executable permissions to the plugin:

chmod 777 /usr/local/nagios/libexec/check_cpu_stats

I'm not 100% sure if this plugin is fully compatible with the version of your server. After you upload it and set permission run this command in the command line, on the Solaris server and make sure the plugin works OK:

/usr/local/nagios/libexec/check_cpu_stats -w 70,40,30 -c 90,60,40

[anilgupta]

Thanks npolovenko!

Great. I think the previous version of the command didn't work because you have the following option disabled in the nrpe.cfg:

I enabled the option by changing

Code: Select all

dont_blame_nrpe=1

changed the command as:

Code: Select all

command[check_disk]=/usr/local/nagios/libexec/check_disk $ARG1$

After nrpe restart, I get below message for the check_disk

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[guptaa@cacbigdcapmdw51 ~]$ /usr/local/nagios/libexec/check_nrpe -H 10.92.34.66 -t 30 -c check_disk -a '-w 20% -c 10% -p /'
CHECK_NRPE: Receive header underflow - only 0 bytes received (4 expected).

Yep, that's the problem. Because all this command does is it points to the plugin installed locally on the solaris server.

I downloaded the file under libexec and executed chmod 777 against the file. The result is not as expected.

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[guptaa@cacbigdcapmdw51 ~]$  /usr/local/nagios/libexec/check_nrpe -H 10.92.34.66 -t 30 -c check_cpu_stats -a '-w 70,40,30 -c 90,60,40'
CHECK_NRPE: Receive header underflow - only 0 bytes received (4 expected).

Please suggest.

[npolovenko]

@anilgupta, Please put the following option somewhere in the middle of the nrpe.cfg file:

allow_bash_command_substitution=1

And restart the nrpe agent. Try running the check_disk command again.
It could also be that this particular nrpe agent is old and was initially configured not to accept arguments.


As far as check_cpu_stats, please run the command I suggested in the previous message:

/usr/local/nagios/libexec/check_cpu_stats -w 70,40,30 -c 90,60,40

And let me know if it works. This command needs to be executed on the Solaris server.

[anilgupta]

And restart the nrpe agent. Try running the check_disk command again.
It could also be that this particular nrpe agent is old and was initially configured not to accept arguments.

After adding

Code: Select all

allow_bash_command_substitution=1

in nrpe.cfg and restarting nrpe. I see same error message, please see attached nrpe.cfg

Code: Select all

[guptaa@cacbigdcapmdw51 ~]$ /usr/local/nagios/libexec/check_nrpe -H 10.92.34.66 -t 30 -c check_disk -a '-w 20% -c 10% -p /'
CHECK_NRPE: Receive header underflow - only 0 bytes received (4 expected).

As far as check_cpu_stats, please run the command I suggested in the previous message:

I get the output when I run it on Solaris server.

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bash-3.2# /usr/local/nagios/libexec/check_cpu_stats -w 70,40,30 -c 90,60,40
CPU STATISTICS OK : user=0% system=0%, iowait=0%, idle=100%, nice=0.00%, steal=0.00% | CpuUser=0%;70;90;0; CpuSystem=0%;40;60;0; CpuIowait=0%;30;40;0; CpuIdle=100%;0;0;0; CpuNice=0.0%;0;0;0; CpuSteal=0.0%;0;0;0;
bash-3.2# 

however, it is breaking from Nagios Server.

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[guptaa@cacbigdcapmdw51 ~]$ /usr/local/nagios/libexec/check_nrpe -H 10.92.34.66 -t 30 -c check_cpu_stats -a '-w 70,40,30 -c 90,60,40'
CHECK_NRPE: Receive header underflow - only 0 bytes received (4 expected).