Bug#552563: auto-create preseed.cfg file

[Philip Hands <phil@hands.com>]

On Wed, Oct 28, 2009 at 03:08:50PM +0100, martin f krafft wrote:
> also sprach Holger Levsen <holger@layer-acht.org> [2009.10.28.1121 +0100]:
> > On Dienstag, 27. Oktober 2009, martin f krafft wrote:
> > > Since debconf-get-selections is not the appropriate way to create
> > > preseed.cfg files,
> > 
> > why not? because you think it's hackish, suboptimal or..?
> 
> So says the documentation.

The main problem here is that the preseed.cfg is supposed to be a
minimal specification of the admin's intent, whereas the output of
debconf-get-selections is a splodge of things from which that intent might
be partially discernible, mixed in with things that would be irrelevant
or dangerous to specify when preseeding.

If we were to add some hints to the question templates to indicate how
relevant a question is to preseeding, along with perhaps a udeb for
asking the intent questions that are vital to an auto-install, but will
never get asked in a manual install, then we might be able to generate
a preseed.cfg that would be at least a useful starting point.

When generating the preseed.cfg, if we did that by iterating over the
udebs that provided the questions, we could allow individual udebs to
provide a preseed.cfg generator script that would override the default
output generator, so that things like partman could spit out something
that included specialised settings, and a chunk of comments about what
you need to make it usable.

As a very simplistic start, we could have a flag indicating that the
question was preseed-irrelevant, and make the resulting preseed.cfg
look much like debconf-get-selections, but with the irrelevant questions
commented out, and a chunk of the standard default preseed.cfg stuck on
the top.

I'd also like to see the output stage accepting hooks with which I could
override the output generation stage with something that would split
the preseed.cfg up in a way that would be suited to dropping it into my
hands-off scheme.

Perhaps off topic, but related, it would be great if we had a way of
detecting that a preseed.cfg was using old question names that had been
superseded -- so that when a question changed in a backwards incompatible
way, rather than things just going weird, one would get an error
suggesting that the preseed.cfg needs updating, and the install would
bail out.

Cheers, Phil.