[rrd-users] setting last_update

[Alex van den Bogaerdt]

On Thu, Feb 15, 2007 at 08:11:06AM -0500, Dan Langille wrote:
> My short term goal is to reset last_update in an rrd file.  Long 
> term, I'd like to find the cause of the very large value contained 
> therein.
> 
> The problem occurs on a system running FreeBSD 6.2 with an amd64 
> kernel.

Hmmm...  64-bit.  You may very well have found a bug.  Not necessarily
in RRDtool, perhaps a library or so.

> I encountered these errors yesterday:
> 
> rrd_update:illegal attempt to update using time 1171508010 when last 
> update time is 94450340160
> 
> The first date looks OK. The second does not.

Indeed.

> Looking at the rrd file:
> 
> # rrdtool info  cpu0.rrd | head
> filename = "cpu0.rrd"
> rrd_version = "0003"
> step = 5
> last_update = 944503401600
> 
> 
> Notice the date, that's a bit odd:
> 
> # date -r 944503401600
> Wed Feb 14 00:00:00 PST 31900

Using GNU date:
$ date -u -d 19700101\ 00:00\ 94450340160\ seconds
Mon Oct  7 07:14:08 UTC 1968


I'm not saying that this is more correct, I'm just noticing a difference.

[snip: good on i386]


> Failing a solution, does anyone know how to reset the last_update 
> field in an rrd file?

you could try a dump-restore cycle.  But I would pay much attention
to the rest of the file as well.

$ rrdtool dump my.rrd|head -7
<!-- Round Robin Database Dump -->
<rrd>
        <version> 0003 </version>
        <step> 60 </step> <!-- Seconds -->
        <lastupdate> 1171548181 </lastupdate> <!-- 2007-02-15 15:03:01 CET -->

        <ds>


HTH
-- 
Alex van den Bogaerdt
http://www.vandenbogaerdt.nl/rrdtool/