On Sun, 22 Nov 2009, Dennis Kibbe wrote: > "The upstream maintainer of yum, Seth Vidal, had the following to say > about 'yum priorities' in September 2009: > > Gosh, I hope people do not set up yum priorities. There are so many things > about priorities that make me cringe all over. It could just be that it > reminds me of apt 'pinning' and that makes me want to hurl." > > This note was placed on the wiki (PackageManagement/Yum?Priorities) > without any explanation why yum-priorities isn't a good idea.
Hi, Dennis That page is outlinked from the general discussion on Respositories, which runs through a discussion of 'exclude' and 'includepkg' as earlier options to consider before these two non-stock install addons to yum that you mentioned. The problem with priorities, and pinning generally, is that it cannot anticipate the growth of package dependencies, and tries to solve with a static rule, a shifting problem. It may work to get what is initially wanted, but it is a durable solution, nor the right solution, because eventually, some combination of enhanced weighting will cause an unintended consequence, blocking some more important upgrade [a point version bump, or worse a security async update]. We see it a lot in the IRC channel with people who don't or won't read, and with the intermitent availability of some non-CentOS archives, and yet want the system to solve integrating encumbered sound driver codecs and extensions. They do, sometimes withthis approach, or forcing or much worse --nodeps, and later have the 'wheels come off' when some library dependency on a main archive is blocked by an upgrade path not anticipated or tested by the adjunct archive maintainer. It is usually safe to drill in a binary package out at the leaf nodes from an external archive -- but these encumbered packages have a witches brew of libraries they need as well, and when upgrades on the main line are issued, one can end up with an unsolvable set of dependencies for the old, and requirements by the new. 'priorities' falls over and dies at that point from self-induced dependency hell, and CentOS is blamed for it in the back splatter. I was the wiki article editor who initially added that caveat section, after seeing priorities being pushed as the 'best' alternative. It is not. It is more like Russian roulette without peeking at the state of the chamber, for your installation. The mentioned 'exclude' and 'includepkg' approach is more correct, but also requires reading the yum and rpm man pages, and gaining some understanding of dependencies. -- Russ herrold _______________________________________________ CentOS mailing list CentOS@centos.org http://lists.centos.org/mailman/listinfo/centos
