The document details the NRPE (Nagios Remote Plugin Executor) which allows the execution of plugins and scripts on client machines by a Nagios server. It outlines the components, installation processes, daemon configuration, variable handling, and command definitions associated with NRPE across different Linux distributions. Additionally, it includes installation scripts, configuration file locations, and examples of service checks and commands used in Nagios monitoring.

1. NRPE
Nagios Remote Plugin Executor
Mike Weber
mweber@spidertools.com

2. NRPE Concepts
Agent Required on Client
* plugin or script executes locally
* daemon runs on client (port 5666)
Nagios
* check_nrpe connects to client
Direct Checks
* connect and collect data from client
Indirect Checks
* connect to client, execute plugin to connect to second client
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3. Basic Concepts
2012 3

4. NRPE: Active and Indirect Checks
2012 4

5. NRPE Components: Client
NRPE Daemon
* daemon managed by xinetd
* security based on allowed_hosts
* runs on port 5666
* open firewall
NRPE Commands File (nrpe.cfg)
* check_nrpe connects to client
* command definitions
Plugins
* connect and collect data from client
2012 5

6. NRPE Components: Server
One Plugin
* check_nrpe (installed by default in XI)
Host and Service Definitions
* define the host
* define each service
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7. NRPE Variables

8. NRPE Variables: Client
Agent Install
* repository (CentOS, SUSE,Ubuntu, Debian, etc.)
* XI agent from wizard
* compile
Daemon Install
* repository (CentOS, SUSE,Ubuntu, Debian, etc.)
* compile
nrpe.cfg
* repository (CentOS, SUSE,Ubuntu, Debian, etc.)
* compile
Command Definitions
2012 8

9. Client Variables: Daemon and Config
Program
/usr/local/nagios/bin/nrpe
/usr/sbin/nrpe
Daemon Config
/etc/xinet.d/nrpe
/etc/nagios/nrpe
/etc/nagios3/nrpe (Ubuntu)
2012 9

10. NRPE: Daemon Config - nrpe
# 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 = 127.0.0.1 192.168.5.99
}
2012 10

11. Client Variables: Commands File
Location
/usr/local/nagios/etc/nrpe.cfg (compile)
/usr/local/nagios/etc/nrpe/common.cfg (XI Agent)
/etc/nagios/nrpe.cfg (SUSE)
/etc/nagios3/nrpe.cfg (Ubuntu)
Definitions
* able to use arguments
* dont_blame_nrpe=1
command[check_users]=/usr/local/nagios/libexec/check_users -w $ARG1$ -c $ARG2$
* unable to use arguments
* dont_blame_nrpe=0
command[check_users]=/usr/local/nagios/libexec/check_users -w 2 -c 4
2012 11

12. Client Variables: Plugins Location
/usr/local/nagios/libexec
/usr/lib/nagios/plugins
/usr/lib64/nagios/plugins
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13. NRPE Compile

14. Why Compile NRPE and Plugins?
Eliminate Variables Across Distribution
* same daemon settings and location
* same nrpe definitions
* same commands locations and configuration (nrpe.cfg)
* same location for plugins
* same versions
Uniform Troubleshooting
* standards across distributions
* easier for multiple administrators
Uniform Upgrades
* method of upgrade the same
* upgrades will be the latest
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15. NRPE: Install Script
#!/bin/bash
if [[ $EUID -ne 0 ]]; then
echo "This script must be run as root" 1>&2
exit 1
fi
cd /tmp
wget http://sourceforge.net/projects/nagios/files/nrpe-2.x/nrpe-2.13/nrpe-2.13.tar.gz/download
tar zxvf nrpe-2.13.tar.gz
cd nrpe-2.13
yum install -y mod_ssl openssl-devel xinetd gcc make
./configure --with-ssl=/usr/bin/openssl --with-ssl-lib=/usr/lib
make
make install
make install-daemon
make install-daemon-config
make install-xinetd
cp sample-config/nrpe.cfg /usr/local/nagios/etc/
2012 15

16. Plugins: Install Script
#!/bin/bash
if [[ $EUID -ne 0 ]]; then
echo "This script must be run as root" 1>&2
exit 1
fi
cd /tmp
wget http://sourceforge.net/projects/nagiosplug/files/nagiosplug/1.4.16/nagios-plugins-
1.4.16.tar.gz/download
yum install -y gcc make mysql-devel mysql net-snmp
useradd nagios
groupadd nagcmd
usermod -a -G nagcmd nagios
tar zxvf nagios-plugins-1.4.16.tar.gz
cd nagios-plugins-1.4.16
./configure --with-nagios-user=nagios --with-nagios-group=nagios
make
make install
exit 0
2012 16

17. NRPE: Locations When Compiled
Daemon Configuration
/etc/xinetd.d/nrpe
Daemon Binary
/usr/local/nagios/bin/nrpe
Configuration File
/usr/local/nagios/etc/nrpe.cfg
Plugins
/usr/local/nagios/libexec
2012 17

18. NRPE: XI Agent

19. CentOS Agent: XI
cd /tmp
wget http://assets.nagios.com/downloads/nagiosxi/agents/linux-nrpe-agent.tar.gz
tar zxvf linux-nrpe-agent.tar.gz
cd linux-nrpe-agent
./fullinstall
Allow from: 192.168.5.184
Stopping xinetd: [ OK ]
Starting xinetd: [ OK ]
Subcomponents installed OK
RESULT=0
##########################################################
### ###
### Nagios XI Linux Agent Installation Complete! ###
### ###
##########################################################
2012 19

20. NRPE: Locations XI Agent
Daemon Configuration
/etc/xinetd.d/nrpe
Daemon Binary
/usr/local/nagios/bin/nrpe
Configuration File
/usr/local/nagios/etc/nrpe.cfg
include_dir=/usr/local/nagios/etc/nrpe
dont_blame_nrpe=1
/usr/local/nagios/etc/nrpe/common.cfg
Plugins
/usr/local/nagios/libexec
2012 20

21. common.cfg
### GENERIC SERVICES ###
command[check_init_service]=sudo /usr/local/nagios/libexec/check_init_service $ARG1$
command[check_services]=/usr/local/nagios/libexec/check_services -p $ARG1$
### MISC SYSTEM METRICS ###
#command[check_users]=/usr/local/nagios/libexec/check_users -w 5 -c 10
command[check_users]=/usr/local/nagios/libexec/check_users $ARG1$
command[check_load]=/usr/local/nagios/libexec/check_load $ARG1$
command[check_swap]=/usr/local/nagios/libexec/check_swap $ARG1$
command[check_cpu_stats]=/usr/local/nagios/libexec/check_cpu_stats.sh $ARG1$
command[check_mem]=/usr/local/nagios/libexec/custom_check_mem $ARG1$
### YUM UPDATES ###
command[check_yum]=/usr/local/nagios/libexec/check_yum
### DISK ###
command[check_disk]=/usr/local/nagios/libexec/check_disk $ARG1$
command[check_ide_smart]=/usr/local/nagios/libexec/check_ide_smart $ARG1$
### PROCESSES ###
command[check_all_procs]=/usr/local/nagios/libexec/custom_check_procs
command[check_procs]=/usr/local/nagios/libexec/check_procs $ARG1$
### OPEN FILES ###
command[check_open_files]=/usr/local/nagios/libexec/check_open_files.pl $ARG1$
### NETWORK CONNECTIONS ###
command[check_netstat]=/usr/local/nagios/libexec/check_netstat.pl -p $ARG1$ $ARG2$
2012 21

22. Commands: nrpe.cfg
No Variables Allowed
dont_blame_nrpe=0
command <service_check> <path_to_plugin> <plugin> <arguments>
command[check_hda1]=/usr/local/nagios/libexec/check_disk -w 20% -c 10% -p /dev/hda1
Using Variables
dont_blame_nrpe=1
command <service_check> <path_to_plugin> <plugin> <arguments>
command[check_hda1]=/usr/local/nagios/libexec/check_disk -w $ARG1$ -c $ARG2$ -p
$ARG3$
2012 22

23. Downside of Arguments
CentOS
check_cpu_stats!-a '-w 85 -c 95'
SUSE Enterprise
check_cpu_stats!-a -w 80 -a -c 90
2012 23

24. NRPE: Nagios Core

25. NRPE: Active Check
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26. Nagios Core: Service Checks
No Arguments
define service{
use generic-service
host_name centos
service_description Users
check_command check_nrpe!check_users
}
define service{
use generic-service,srv-pnp
host_name centos
service_description Mailq
check_command check_nrpe!check_mailq
}
Arguments
define service{
use generic-service
host_name centos
service_description Disk
check_command check_nrpe_arg!check_disk!80!90!/
}
2012 26

27. Nagios Core: Command Definition
No Arguments
define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}
define command{
command_name check_nrpe_60
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -t 60 -c $ARG1$
}
Arguments
define command{
command_name check_nrpe_arg
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$ -a
$ARG2$ $ARG3$ $ARG4$
}
2012 27

28. Summary
No Arguments
define command{
command_name check_nrpe
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$
}
define service{
use generic-service
host_name centos
service_description Users
check_command check_nrpe!check_users
}
command[check_users]=/usr/local/nagios/libexec/check_users -w 2 -c 4
Arguments
define command{
command_name check_nrpe_arg
command_line $USER1$/check_nrpe -H $HOSTADDRESS$ -c $ARG1$ -a $ARG2$
$ARG3$ $ARG4$
}
define service{
use generic-service
host_name centos
service_description Disk
check_command check_nrpe_arg!check_disk!80!90!/
}
command[check_disk]=/usr/local/nagios/libexec/check_disk $ARG1$
2012 28

29. AIDE: Advanced Intrusion Detection Environment
Script
!/bin/bash
# Create 4 Hour Cron Job With AIDE
logfile=/tmp/aide
x=$(grep "Looks okay" $logfile | wc -l)
if [ $x -eq 1 ]
then
echo "All Systems Look OK"
stateid=0
else
echo "$(egrep "added|changed" /tmp/aide)"
stateid=2
fi
exit $stateid
Command in nrpe.cfg
command[check_aide]=/usr/local/nagios/libexec/check_aide
Service Definition
define service{
use generic-service
host_name bash
service_description AIDE
check_command check_nrpe!check_aide
}
2012 29

30. NRPE: Nagios XI

31. NRPE: Linux Server
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32. NRPE: Linux Server
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33. NRPE: Linux Server
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34. NRPE: Linux Server
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35. NRPE: Linux Server
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36. /etc/init.d
ls /etc/init.d
crond gpm iscsi lvm2-monitor named nscd rawdevices
snmpd sysstat dc_client haldaemon iscsid mcstrans netconsole
ntpd rdisc snmptrapd vsftpd dc_server halt killall
messagebus netfs portmap restorecond snmptt winbind dovecot
httpd kudzu multipathd netplugd postfix saslauthd sshd
xinetd functions iptables lm_sensors mysqld network postgresql-9.0
single syslog
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37. NRPE: Linux Server
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38. NRPE: Linux Server
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39. NRPE: Linux Server
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40. NRPE: Linux Server
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41. NRPE: Additional Checks
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42. NRPE: Additional Checks
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43. NRPE: Additional Checks
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44. NRPE: Questions?