On Thursday, May 24, 2012 03:26:02 PM Les Mikesell wrote:
But many, probably most of those cases are revs with forward/backward compatibility. It's hard to generalize about that, though.
Yep, it sure is. Forward/backward compatibility is almost entirely in the hands of the upstream projects (upstream from Red Hat). Some do that kindof thing well; others do not. Open source not only gives choice to the user, but also transfers the responsibility for choosing wisely to the user making the choice.
Even in the scalpel case you mentioned the up-rev lib was likely compatible but just specified as requiring an exact version in the spec file.
The one that has bitten me the hardest is xrdp. It will bite harder once a release based on FreeRDP rather than rdesktop is released out of git. The compatibility depends entirely on the package's upstream policies, developers, and stage of development (xrdp isn't out of beta, after all).
And on the other side there are things like viewvc that are at the same rev in epel and rpmforge but have slightly different and incompatible configurations (and there is a reason I know that...).
Likewise amavisd-new. It's not rare to have issues, and lots of people have had them, thus my cautions. Not trying to scare anyone off from any third party repository; just want to give information that allows people to make informed decisions, and show people how I at least arrived at my conclusions that work for me with my particular setup; what my particular setup is isn't the important thing, it's how and why I got there that I consider potentially useful to others.
At the moment both EPEL and RPMforge are on a 2.6.x amavisd-new; 2.7 makes some changes in the AM.PDP protocol that can break, for instance, amavisd-milter (distinct from the much less useful amavis-milter). Neither repo has amavisd-milter, so that compatibility issue may not show up except to those who actually use amavisd-milter instead of the much less useful amavis-milter.
I'll step out on a limb here and generalize somewhat; I would think that most CentOS users use at least one third-party repository, if the traffic on this list is any indication (and, again, I reserve the right to be wrong). So knowing how to properly determine how to use those repos (which was the OP's question, after all) is very useful indeed, IMO.
And, again, FWIW, HTH, IMHO, YMMV, etc.