Hello, I'm a relatively new user of CentOS 5.5. The CentOS wiki advises the use of yum priorities if you use more than the base repositories, specifically with RPMForge: http://wiki.centos.org/AdditionalResources/Repositories/RPMForge (I have yum-3.2.22-26.el5.centos and yum-priorities-1.1.16-14.el5.centos.1) As I gather has been stated before on the centos list [1], it also implies that yum-priorities isn't a great solution (quoting Seth Vidal), but stops short of outlining what exactly is wrong with yum-priorities (YP) and why it's still recommended. In fact it goes on to say: > as of yet, no real world problems have been reported with regard to the > 'yum-priorities' plugin So, I experienced a real-world problem (more details in [2]): - set CentOS base with priority 1 - set RPMForge with priority 2 - yum check-update was ok - yum update seemed ok, prompted to proceed, then aborted half way. It aborted because of an unresolvable dependency from an RPMForge package, where the package which satisfies it hidden by an older version in the base repo. Specifically: perl-Module-Install-0.92-1.el5.rf needed perl-Archive-Tar >= 1.44 At first I thought RPMForge must be broken, because there seemed to be nothing which would satisfy the dependency, just this: $ yum list --showduplicates perl-Archive-Tar perl-Archive-Tar 1.30 centos-base RPMForge appears to have nothing at all. Later I inferred yum-priorities was hiding it from view, because with --noplugins, yum would admit that indeed the required perl-Archive-Tar-1.44 did exist in RPMForge: $ yum list --showduplicates --noplugins perl-Archive-Tar perl-Archive-Tar 1.30 centos-base perl-Archive-Tar 1.44 rpmforge So RPMForge was not broken, I just have an pathological case of yum-priorities. Of course, I know this is what yum-priorities is designed to do, and that it isn't perfect. I have two suggestions, however - but they seem a bit obvious, so before I file them on the yum issue tracker I'd like to check I've not missed anything. Firtly, the fact that yum+YP hides packages so completely they don't seem to be present can be confusing, and it'd be nice if that could be fixed so that --showduplicates will report the presence of packages which won't be installed because of YP. However, the bigger problem is that yum does *not* seem to be able to detect the kind of unresolvable dependency problem I experienced. Therefore it happily starts the update process, only to abort with an error half way through, leaving my system essentially broken. Neither does yum check-update warn me about this risk. My choice seems to be: - don't use yum-priorities, but get into a muddle when base OS packages get replaced, or - do use it, but at the risk of breaking my (possibly production) server at an unpredictable moment entirely outside my control (as described). Couldn't yum check-update and yum update detect the dependency problem and warn me at a point I can still back off? For example, in a case like the one above, couldn't yum update check the dependencies available and refuse to proceed, telling me something like this? perl-Module-Install-0.92-1.el5.rf needs perl-Archive-Tar >= 1.44, but perl-Archive-Tar-1.44 from the 'rpmforge' repo cannot be used due to the presence of perl-Archive-Tar-1.30 the higher priority repo 'centos-base'. See [link to documentation] for possible ways to resolve this problem. Thanks, Nick --- 1. http://thread.gmane.org/gmane.linux.centos.general/86563 2. An example of when yum_priorities bites included here: http://www.noodlefactory.co.uk/~nick/wu-lee/Notes/YumPrioritiesPitfalls _______________________________________________ Yum mailing list Yum@xxxxxxxxxxxxxxxxx http://lists.baseurl.org/mailman/listinfo/yum
