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mrtg-rrd - How to use RRDtool with MRTG
After using MRTG for some time you may find some limitations. Mostly in the areas of per-
formance and graphing flexibility. These are exactly the areas addressed by rrdtool. To
learn more about RRDtool check out its website on
When using mrtg with RRDtool you are replacing rateup with the RRDtool perl module
RRDs.pm. To enable RRDtool support in mrtg you have to add the line
MRTG needs access to both the RRDtool perl module RRDs.pm and to the rrdtool executable.
If these two items are not installed in locations where perl can find them on its own,
then you can use the following two parameters to supply the appropriate directories.
For the location of the rrdtool executable you put
For the location of the perl module it would be:
When you have made this modification to the configuration file, several things will happen
when you run mrtg again with the new config file:
1. mrtg will take all your old ".log" files and convert them to ".rrd" format. (The
".log" files don't get touched in the process, so if things don't work out they are
2. mrtg will use rrdtool to update its databases. These will have a new format called rrd
which is totally different than the native log format of the classic mrtg.
3. mrtg will not create any webpages of graphs anymore. It will only query the routers
for traffic information and update its rrd databases.
The advantage of whole thing is that the mrtg will become much faster. Expect the runtime
to drop to 20% of the previous value. (I would like to get some feedback on this from
folks with large installations)
Mind you though, while the logging process of RRDtool is very fast, you are also gaining
some time by neither creating graphs nor updating webpages. The idea behind this is that
it is more efficient to create graphs and webpages on demmand. Using a cgi script.
At the moment there is no official script to do this, but two contributers have created
Was the first program to take over the webpage creation and graphing task. It has
been developed by Rainer Bawidamann <Rainer.Bawidamann@informatik.uni-ulm.de>. You can
find a copy on Rainers website:
The program comes with its own documentation
routers.cgi, servers.cgi and generic.cgi
are other cgi frontends to mrtg running with rrdtool. Thier main difference to 14all
is, that the web pages it creates are much more stylish than the ones from mrtg. These
tools have been written by Steve Shipway <firstname.lastname@example.org>. You can find a
The scripts comes with their own installation instructions.
Just as a side note: MRTG-3 will be based entirely on rrdtool technology. But don't wait
for it ... get going now!
Tobias Oetiker <email@example.com>
3rd Berkeley Distribution 2.9.17 MRTG-RRD(1)
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