questions on package management

[lee]

Kevin Fenzi <kevin at scrye.com> writes:

> 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. 

Assuming that package A doesn't work with the more recent version of
package C?

>> + 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. 

That would make sense if A doesn't work with the more recent version of
C.

>> 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. 

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. 

Yes, this situation was the result of an upgrade that didn't finish.  Are
you saying that 'yum list installed' doesn't really tell you what is
actually installed and you need to use 'rpm -V' instead?

What are these placeholders?

And file dependencies change with pre-linking:

prelink: /usr/bin/cjet: at least one of file's dependencies has changed since prelinking

Pre-linking it again should fix that?


-- 
Fedora 19