[rrd-users] About rrdtool dump method

[Pablo Sanchez]

[ Comments below, in line ]

On Tuesday 22 June 2010 at 11:51 am, Howard Jones penned
about "Re: [rrd-users] About rrdtool dump method"

> On 22/06/2010 16:45, Wagner Pereira wrote:
> > -------------------
> > cacti:/var/lib/cacti/rra# rrdtool dump alpine_traffic_in_29.rrd > 
> > alpine_traffic_in_29.rrd
> > ERROR: mmaping file 'alpine_traffic_in_29.rrd': Invalid argument
> >   
> You are dumping the rrd file onto itself! The second filename should be
> something.xml
> 
> That is why you end up with a 0 length file.

Elaborating on Howard's post.

The `> alpine_traffic_in_29.rrd' instructs the shell _before_
executing the command to `if the file `alpine_traffic_in_29.rrd' does
not exist, create it.  If it does exist, truncate the file'

I suspect the subsequent error (`ERROR: mmaping file
'alpine_traffic_in_29.rrd': Invalid argument') comes from `rrdtool
dump' complaining about the file format:  there's no data in the just
clobbered file.

Cheers,
-- 
Pablo Sanchez - Blueoak Database Engineering, Inc
Ph:    819.459.1926      Fax:   760.860.5225 (US)