Hi,
well, i note there's a few versions of rrdtool in the various repositories. the stock CentOS 5 version 9from upstream) is 1.2.30, while rpmforge has 1.3.7, also a seperate rrdutils package (I have no idea whats in it)
*sigh* The stuff of nightmares, I did have 1.3.7 installed after checking. But searching on this direction finally yielded an important piece of information. Somebody posted back in 2008 on a site to IGNORE the jrrd problem because OpenNMS supposedly comes with some kind of java rrd already installed (which begs the question of why then is the jrrd step mentioned in the install guide).
So I went ahead with the install process which then complained that my postgresql was the wrong version, i.e. 8.4 instead of max of 8.3, but at least this time it kindly offered a -Q option to ignore the version restrictions at my own risk.
I did. Then it was on to another problem, with OpenNMS dying on startup due to port clash with DHCP. Fortunately again, this was noted as something that happens quite often on Linux systems and a quick fix was to simply comment out the dhcp configuration.
After that, it was just the usual matter of opening a port in iptables for the opennms/tomcat and FINALLY something was working.
I'm crossing my fingers that ignoring the jrrd, ignoring the versions and ignoring the dhcp monitor isn't going to bite me one of these days. For now, "ignore"nce is bliss :D