2007 May 04 - Fri

Configuring eSensors with Nagios

The EM01B WebSensor from Esensor (http://www.eesensors.com/websensor.html) provides Temperature, Humidity, and Illumination values to Nagios.

Download the source code for the Nagios plugin from http://www.nagiosexchange.org/Environmental.60.0.html?&tx_netnagext_pi1[p_view]=13 and place it into the /usr/src directory. Unzip it to a directory called esensors. Change into /usr/src/esensors/c and run:

gcc check_em01.c -o check_em01
cp check_em01 /usr/local/nagios/libexec/

Ignore the warnings.

Add the following llnes to /usr/local/nagios/etc/checkcommands.cfg:

# 'check_temp' command definition
define command{
            command_name check_temp
            command_line $USER1$/check_em01 $HOSTADDRESS$ T $ARG1$ $ARG2$ $ARG3$ $ARG4$
            }
# 'check_humidity' command definition
define command{
            command_name check_humidity
            command_line $USER1$/check_em01 $HOSTADDRESS$ H $ARG1$ $ARG2$ $ARG3$ $ARG4$
            }
# 'check_light command definition
define command{
            command_name check_light
            command_line $USER1$/check_em01 $HOSTADDRESS$ I $ARG1$ $ARG2$ $ARG3$ $ARG4$
            }

Create a file named /usr/local/nagios/etc/srvc_esensor.cfg with the following content:

###############################################################################
#
# Configuration file for eSensor Devices
#
# Last Modified: 2006-06-08
#
################################################################################

################################################################################
# SERVICE DEFINITIONS
################################################################################
# Generic service definition template
define service{
        name                            generic-esensor ;  Referenced in other service definitions
        active_checks_enabled           1       ; Active service checks are enabled
        passive_checks_enabled          1       ; Passive service checks are enabled/accepted
        parallelize_check               1       ; Active service checks should be parallelized
        obsess_over_service             1       ; We should obsess over this service (if necessary)
        check_freshness                 0       ; Default is to NOT check service 'freshness'
        notifications_enabled           1       ; Service notifications are enabled
        event_handler_enabled           1       ; Service event handler is enabled
        flap_detection_enabled          1       ; Flap detection is enabled
        process_perf_data               1       ; Process performance data
        retain_status_information       1       ; Retain status information across program restarts
        retain_nonstatus_information    0       ; Retain non-status information across program restarts
        register                        0       ; DONT REGISTER THIS DEFINITION
        is_volatile 0
        check_period 24x7
        max_check_attempts 3
        normal_check_interval 5
        retry_check_interval 1
        contact_groups sensor-admins
        notification_interval 30
        notification_period 24x7
        notification_options d,u,r
        }
# check temp service definition template
define service{
        use                             generic-esensor
        name                            etemp-service   ; Referenced in other service definitions
        register                        0       ; DONT REGISTER THIS DEFINITION
        service_description Temperature
        check_command check_temp!2!110!1!120
        }
# check humidity service definition template
define service{
        use                             generic-esensor
        name                            ehum-service    ; Referenced in other service definitions
        register                        0       ; DONT REGISTER THIS DEFINITION
        service_description Humidity
        check_command check_humidity!2!90!1!99
        }
# check light service definition template
define service{
        use                             generic-esensor
        name                            eillum-service  ; Referenced in other service definitions
        register                        0       ; DONT REGISTER THIS DEFINITION
        service_description Illumination
        check_command check_light!2!600!1!700
        }

Add the following line to /usr/local/nagios/etc/nagios.cfg:

cfg_file=/usr/local/nagios/etc/srvc_esensor.cfg

Create a file called /usr/local/nagios/etc/examplecom/em01.cfg with the following content:

define host{
        use                             generic-host
        host_name                       em01
        alias                           Heat, Humidity and Illumination tests
        address                         10.1.6.30
        }

define hostgroup{
        hostgroup_name  	Esensors
        alias          		Esensors HVAC sensor
        members         	em01
        }

define servicegroup{
        servicegroup_name       esensors
        alias                   Enviromental Monitoring
        members                 em01,Temperature
        members                 em01,Humidity
        members                 em01,Illumination
        }

define service {
        use                     etemperature-service
        host                    em01
        check_command           check_temp!60!80!50!85
        }

define service {
        use                     ehumidity-service
        host                    em01
        }

define service {
        use                     eillumination-service
        host                    em01
        }

As a side note, I think I'm going to process esensor output with something else. Here is a brief regular expression in a perl file called 'em.pl' to handle the output:

use strict;

my $a = <STDIN>;
$a =~ m/TF:[ ]*(\d+\.\d+).*HU:[ ]*(\d+\.\d+).+IL[ ]*(\d+\.\d+)/;
print "$1, $2, $3\n";

The following command line generates three values (using the tool 'curl' to obtain the current values):

echo `curl -s http://bmem01/index.html?em123456` | perl em.pl

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