[rrd-users] Fetch the time of the first entry

Steven Sim unixandme at outlook.com
Tue Jul 1 15:29:42 CEST 2014


Something is seriously wrong and I don't know what it is.

My Perl script parses the data file just fine.

It plots just fine.

The legends are correct

The dates are correct.

BUT when I use rrdtool first <rrd database> in an attempt to get the time
of the first entry, I get a Unix time stamp which is one entire month
EARLIER than the first entry in the file.

And each time I do update, rrdtool first <rrd_database> returns a DIFFERENT

The rrd database is created with an RRA sufficient to contain an entire
month with readings taking every 15 minutes (900 seconds).

I would appreciate any suggestions.

Deepest Regards
Steven Sim

On Tue, Jul 1, 2014 at 8:23 PM, Simon Hobson <linux at thehobsons.co.uk> wrote:

> Steven Sim <unixandme at outlook.com> wrote:
> > my rrdtool first <rrdfile> command keeps returning different timing
> after each rrdtool update.
> >
> > Why is that so?
> >
> > Shouldn't it ALWAYS return the Unix time stamp for the first entry?
> It's not a function I've used ...
> The docs say it should return the first value entered. Once you've
> "filled" a data set, then it's going to give you the timestamp of the
> oldest available value - I'm not sure what it gives you for an RRD file
> that hasn't been "filled".
> Here I'm using the term "filled" to mean you done enough updates that the
> whose database (or at least data series) has been filled with data and you
> are now losing older data to make way for the new data.
> Have you looked at how the value is changing ? Does it by any chance
> advance at the same rate as the timestamp of your updates ?
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