[mrtg] Re: changing historical data in an RRD

Eric Brander Eric_Mailing_List at rednarb.com
Wed Jul 21 21:22:38 MEST 2004

Eric Brander wrote:

> [Posted to both the MRTG list and RRD-Users list]
> I've made a mistake in my config file in monitoring some devices. It 
> turns out I've reversed the in and out OIDs on the target line so what's 
> labeled as input is actually output and what's labeled as output is 
> actually input.
> I could simply change my legend to reflect the correct direction but I 
> would prefer to keep the in/out consistent with other devices I'm 
> monitoring.
> I could just start over, or make the change and have it be "correct" 
> from this point forward, but I'd really like the historical data to be 
> accurate as well (6-months worth).
> Do you know of an easy way, or perhaps of a script, that could modify an 
> RRD and exactly swap the in and out data positions?  I don't even know 
> how to spell XML so manually modifying an RRD export for each interface 
> is out of the question. :(
> You suggestions are sincerely appreciated.
> Regards,
> Eric Brander

First, sorry for posting using the wrong subject.

Second, thanks for the suggestion Andrea but I couldn't reply to it for 
some reason as it was in an odd format.

I can not use the reversing technique you described in this instance as 
I am using explicit OIDs.  For example:

. at a.b.c.d

Quite simply, I need to reverse those OIDs so that the .45.1 is first 
(the Inflow) and .44.1 is second (the outflow).  That's simple enough, 
and has the same effect as the reversing suggestion you had.  I'll be 
making this change.

However, once I do that, my historical data will still be inaccurate. 
I'm looking for a solution to modifying the RRD so that I can swap the 2 
values for historical data.  If I weren't using RRD this would be a 
snap; simply cut and past the columns of data to their appropriate spots.

Also, I know I can do an RRDTool export and get the data in an XML 
format, but manipulating that data is my weak point. So I'm looking for 
help on hacking the data in the RRD.

Thanks for reading.


Eric Brander

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