[rrd-users] [FORGED] graph question

Steve Shipway s.shipway at auckland.ac.nz
Sun Nov 22 21:37:59 CET 2015

Use rrdtool info /opt/templog/data/templog.rrd and check to make sure that the ‘internal’ and ‘external’ DS really do have -55 as the lowerlimit and not 0.  The behaviour you describe looks like the lower limit is set to 0 (as the data seem to be absent from the RRD).


You may also wish to verify that you really are storing the data correctly.  It is possible that the script you are using to update the RRD with the temperature data is not correctly handling negative numbers, and is not storing the data successfully.




Steve Shipway

T: +64 9 3737 599 ext 86487

E: s.shipway at auckland.ac.nz <mailto:s.shipway at auckland.ac.nz> 

(GNU Terry Pratchett)


From: rrd-users [mailto:rrd-users-bounces+s.shipway=auckland.ac.nz at lists.oetiker.ch] On Behalf Of s pascal
Sent: Saturday, 21 November 2015 4:27 p.m.
To: rrd-users at lists.oetiker.ch
Subject: [FORGED] [rrd-users] graph question


Hi ,

i have this code to create the graph file

rrdtool graph /var/www/temp_graph.png \
-w 1024 -h 400 -a PNG --slope-mode \
--start -1d --end now \
--vertical-label "temperature (C)" \
DEF:out=/opt/templog/data/templog.rrd:internal:AVERAGE \
DEF:in=/opt/templog/data/templog.rrd:external:AVERAGE \
LINE2:in#00ff00:"inside" \

And this file to create the rrd file:

rrdtool create /opt/templog/data/templog.rrd --step 300   \
DS:internal:GAUGE:600:-55:125  \
DS:external:GAUGE:600:-55:125  \
RRA:AVERAGE:0.5:1:576    \
RRA:AVERAGE:0.5:3:1344   \
RRA:AVERAGE:0.5:12:1488  \
RRA:AVERAGE:0.5:72:1984  \
RRA:MIN:0.5:72:1984      \


But when i create the graph, the temperature curve shows only positive temperature and not negative temperature.

When the temperature is going under 0 C, the curve is blank then become visible when temperature is positive.

How can i resolve this problem?

Thank you

Best Regards

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