questions on package management

[lee]

"Eddie G. O'Connor Jr." <eoconnor25 at gmail.com> writes:

> On 07/13/2013 10:07 AM, lee wrote:
>> "Eddie G. O'Connor Jr." <eoconnor25 at gmail.com> writes:
>>
>>> On 07/12/2013 09:11 PM, lee wrote:
>>>> 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'.
>>>>
>>>> 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.)
>>>>
>>>>
>>> Hmm....well I'm not sure how I would go about fixing that.....maybe
>>> just purge them all and get the latest versions from the repo?....
>> What I did was removing the F17 packages.  Still I'm curious, it's
>> surprising that it is possible to have two versions of the same package
>> installed.
>>
>>
> I believe it's because everything regarding Linux is a "file" of some
> sort, and you can have multiple files on your machine with the same
> name, maybe not EXACTLY the same...but "close enough".

There can be only one '/bin/ls' (unless you replace the file while it's
still open; in that case, the old one invisibly stays (or something like
that) until it's closed).

Think of emacs or a library, you can replace the file and it will
continue to be used by whatever used it before you replaced it.  Start
another instance of emacs or of a software that uses the library after
replacing emacs or the library, and the new version will be used.

That's why it's sometimes a good idea to reboot after upgrades.

> (LibreOffice 4.0.0...and LibreOffice 4.0.1...not the same...but not
> that different either!) I usually try to keep one instance of every
> app in/on my machine, and the stuff that builds up over time that I
> know isn't needed? I delete....(I especially like the "Bleach Bit" app
> and "YumEX" for helping in that regard!!)

You find that updating something like LO from 4.0.0 to 4.0.1 doesn't
remove 4.0.0?  Isn't that exactly one of the things the package
management should take care of?

Imagine upgrading whatever package provides ls from 4.0.0 to 4.0.1 and
having both installed at the same time.  There is still only *one*
/bin/ls, not two of them.  Which one is it gona be?


-- 
Fedora release 19 (Schrödinger’s Cat)