[mrtg] [FORGED] MRTG and IT Watchdog sensor

Steve Shipway s.shipway at auckland.ac.nz
Fri Nov 20 22:36:46 CET 2015

Target[]: tempSensorTemp:tcoe-snmp at<mailto:tempSensorTemp%3Atcoe-snmp at>

You must always give exactly two metrics to MRTG per Target (this is historical, because originally this was inbound and outbound data for network traffic).  If it is a single value, either duplicate it, or use pseudoZero.

Target[]: tempSensorTemp&pseudoZero:tcoe-snmp at<mailto:tempSensorTemp%3Atcoe-snmp at>

This is also assuming, of course, that the symbolic name tempSensorTemp can be expanded to an OID; for this to work, you need to have the MIB properly installed or referred to in the MRTG config file.  Otherwise, you can always use the numerical OID instead.

Now, your OID actually returns the value in deci-degrees, so you need to divide by 10 before storing to make the value an SI unit (Best Practice is to store values as SI units).

Target[]: tempSensorTemp&pseudoZero:tcoe-snmp at  /  10
<mailto:tempSensorTemp%3Atcoe-snmp at>

The spaces around the '/' are required.  This will mean the value is stored in degrees, and will display the correct numbers.  However, if you are not using RRDTool and are just using native MRTG, decimals are not supported in the backend storage, and so you might instead need to do

Factor[]: 0.1

... which will divide by 10 at graphing time instead.

Since you do not want to graph the second item, just use the 'noo' ('No outgoing') option to suppress it.

Options[]: gauge growright noo



Steve Shipway
University of Auckland ITS
UNIX Systems Design Lead
s.shipway at auckland.ac.nz<mailto:s.shipway at auckland.ac.nz>
Ph: +64 9 373 7599 ext 86487


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