[Yum] dependency problems with yum-priorities on CentOS 5.5
office at plcomputers.net
Mon Aug 23 12:05:03 UTC 2010
All you experienced is exactly how it is supposed to be.
Yum-priorities does the following:
ALLWAYS use version of package from repo with lesser priority number.
For all OTHER packages, use version of package with lesser priority number.
I use it like this:
Priority plugin is active always. If I hit dependency problem like you
did, there are two things you can do:
a) do not install package with unresolved dependency
b) run install with "--disableplugin=*prior*" and IGNORE that external
repo will mess with your system, replacing packages yum-priorities is
installed to protect. For smaller insignificant packages I would select
b), but very carefully.
> 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:
> (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 , 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 ):
> - 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.
> 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
> 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
> 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.
> 1. http://thread.gmane.org/gmane.linux.centos.general/86563
> 2. An example of when yum_priorities bites included here:
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> Yum at lists.baseurl.org
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