questions on package management

[Kevin Fenzi]

On Sat, 13 Jul 2013 03:11:20 +0200
lee <lee at yun.yagibdah.de> wrote:

> Hi,
> 
> imagine you have the following:
> 
> 
> package A, depends on C, installed
> package B, depends on C, not installed
> package C, installed
> 
> 
> All the packages are version 1.  After a while, you install package B,
> and in the meantime, package B has been updated to version 2 so that
> it now depends on version 2 of package C.
> 
> What will happen?

Yum will tell you that it can't update because both version 1 and
version 2 of package C are needed and will do nothing. 

> + install B and update A and C?
> + install B and update C and leave A as is?
> + something else?

Error and do nothing. You would be left with version 1 of all packages,
and a consistent system. 

> Another question: It is possible to have version 1 and version 2 of
> package A installed at the same time, like version 1 from Fedora 17
> and version 2 from Fedora 18.  Imagine this package A provides a file
> '/bin/ls'.

No. 

> Which version of '/bin/ls' will be the one in use?  What about
> compatibility issues in such a case?
> 
> (Please don't say it's not possible; I have had it happen.)

It would be whichever package is actually installed. I suspect if you
see this is some case like an upgrade that didn't finish, so it did in
fact update to the new version, but didn't get to the end of the
transaction to remove the placeholder for the old version. 
You can use 'rpm -V' to see which one is actually installed. 

kevin
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