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Re: dh_config_model_upgrade: package upgrade with Config::Model

On Fri, 4 Dec 2009 10:57:51 +0100
Stefano Zacchiroli <zack@debian.org> wrote:

> On Fri, Dec 04, 2009 at 09:08:03AM +0100, Dominique Dumont wrote:
> > The end user may have to answer a medium debconf question asking him
> > whether to upgrade foobar package with Config::Model. Hopefully,
> > that's all the end user will see.
> I wonder why the detail about how the conf file is being upgraded should
> be relevant to the final user at all. As you observe on the wiki page,
> most lusers barely know of the existence of /etc, why should they care
> about Config::Model being used? Ideally, whether to use it or not is a
> choice of the package maintainer.

I also don't understand why Config::Model seeks to replace debconf
questions from the package when Policy is that only programs compatible
with debconf-2.0 are allowed to prompt users during package
installation. (Policy 3.9.1). Config::Model is not debconf-2.0
compatible but tries to mangle compatibility by changing or replacing
the question that debconf would raise. The letter of Policy might be
being followed but the spirit of Policy is being broken IMHO.

Either Config::Model should not ask any questions, ever, or it should
ask one question based on the tasksel settings and determine a set of
answers for each package to suit that configuration model - system-wide.

i.e. a bit like pre-seeding in D-I whereby a set of answers to the
debconf questions can be pre-ordained as "suitable for ModelA" and then
fed to debconf to allow packages to not have to ask any questions and
yet still get a final configuration that matches ModelA. ModelA would
then apply system-wide.

For this to work it would have to encompass ALL packages that use
debconf and therefore it would need to be debconf-2.0 compatible and
fully implementable using cdebconf alone. That doesn't need perl, it
just needs a set of answers to the debconf questions and a POSIX shell
snippet to populate the debconf database. Each Model could have a
different range of answers.

This doesn't seem to be what Config::Model is trying to do, so there is
work to do to explain just what Config::Model *is* meant to do and
precisely which packages are expected to use it. The solution is being
described without the problem being explained.

> Also, assuming that the available configuration on disk matches the old
> model assumed by the package, why bother with a question at all? After
> all dpkg upgrade "untouched" config files automatically, hopefully with
> Config::Model we just introduce a more flexible definition for
> "untouched"

Does Config::Model obey DEBCONF_NONINTERACTIVE_SEEN=true ?


Neil Williams

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