rrdtool and Trixie

TL;DL: if you’re using rrdtool on a 32 bit architecture like armhf make an XML dump of your RRD files just before upgrading to Debian Trixie.

I am an old person at heart, so the sensor data from my home monitoring system¹ doesn’t go to one of those newfangled javascript-heavy data visualization platforms, but into good old RRD files, using rrdtool to generate various graphs.

This happens on the home server, which is an armhf single board computer², hosting a few containers³.

So, yesterday I started upgrading one of the containers to Trixie, and luckily I started from the one with the RRD, because when I rebooted into the fresh system and checked the relevant service I found it stopped on ERROR: '<file>' is too small (should be <size> bytes).

Some searxing later, I’ve⁴ found this was caused by the 64-bit time_t transition, which changed the format of the files, and that (somewhat unexpectedly) there was no way to fix it on the machine itself.

What needed to be done instead was to export the data on an XML dump before the upgrade, and then import it back afterwards.

Easy enough, right? If you know about it, which is why I’m blogging this, so that other people will know in advance :)

Anyway, luckily I still had the other containers on bookworm, so I copied the files over there, did the upgrade, and my home monitoring system is happily running as before.