Specifying How Yum Downloads Updates

[Kevin DeKorte]

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On 04/15/2009 09:09 AM, Bob Gustafson wrote:
> On Wed, 2009-04-15 at 09:38 -0500, Chris Adams wrote:
>> Once upon a time, Bob Gustafson <bobgus at rcn.com> said:
>>> Yes, I'm concerned about the ADDITIONAL packages removed by yum  
>>> because it does not maintain a reference count.
>>>
>>> It happened to me - 152 packages were removed. Many were critical to  
>>> the operation of my system.
>>> A reference counting package manager would not have done that.
>> What is this "reference counting" you keep mentioning?  How would it
>> have helped?
>>
>> You asked yum to do something, it displayed a list of all the actions it
>> was going to take as a result, and you said yes.  What else could it
>> have done?
>>
>> When you tell yum to remove a package that other packages depend on, it
>> can either remove all the dependencies, or not remove anything.
>> Anything else leaves broken packages in the system.  How would some
>> "reference counting" change that?
> 
> Suppose you have a package PkgA which requires libAB, libBB, libC
> 
> On installation of PkgA, it finds that libAB and libBB are already
> installed, having been installed with a previous package PkgB. It does
> install libC.
> 
> If you now remove PkgA, it finds that it depends on libAB, libBB, libC,
> which it displays in a list for the user to decide whether it is ok to
> also delete.
> 
> If the user says Yes, all of the packages PkgA, libAB, libBB, libC are
> deleted, leaving the previously installed package PkgB with missing
> libAB, libBB dependencies.
> 
> A reference counting scheme would detect that libAB and libBB are also
> used by another package and would not delete those two packages. Or
> offer to delete them.
> 

I don't think yum works this way, if you say "remove PkgA" it will only
remove PkgA and the things that depend on PkgA. It will not remove the
libAB,libBB or libC.

That said if you have the remove leaves plugin installed it might try to
remove those as well. However, I have seen that remove leaves does seem
to cause more problems than it fixes. So maybe the plugin needs to be
worked on rather than yum itself.

Kevin

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