What did I just ruin?

[Colin Watson]

On Tue, Jul 10, 2018 at 08:39:13AM +0200, Ralf Mardorf wrote:
> My guess is, that since debconf was "falling back to frontend:
> Readline", the dialog required to answer with "yes" or "no" and nothing
> else, so the "assume-yes" option did exactly this, it always assumed
> "yes", otherwise apt-get would have aborted, see
> http://manpages.ubuntu.com/manpages/xenial/man8/apt-get.8.html .

I'm afraid that your guess is entirely wrong.  apt-get --assume-yes
doesn't influence debconf in any way.

debconf's readline frontend is still perfectly capable of asking
questions, so no harm will have come of this.  The message about
downgrading to a different frontend is essentially informational (but
useful if you were specifically expecting a different frontend).

Even in noninteractive mode (which wasn't what happened here, but is a
further possible fallback), packages are strongly encouraged to have
reasonable default behaviour if they can't ask a question.  In the
corner case where they can't ask a question and there's no reasonable
default, they will normally fail in an obvious way, i.e. causing the
package to fail to configure.  It's not possible to make universal
statements about this since it's up to procedural code in individual
packages' maintainer scripts, but this is the norm.

> However, I wonder what "yes" is for e.g. a config related "default
> action", see
> http://manpages.ubuntu.com/manpages/cosmic/man1/dpkg.1.html , if neither
> the dpkg option "force-confnew" or "force-confold" is used.

The default action depends on the state of the conffiles being
processed.  For example, if the existing file is unmodified from that in
the previously-installed version of the package then the default action
is to install the new version of the file, whereas if it's been modified
locally then the default action is to keep the old version.

In any case, this is irrelevant here, since that didn't happen here and
merely using script(1) wouldn't have caused dpkg to be unable to ask
conffile questions.

Furthermore, apt-get --assume-yes also doesn't affect dpkg conffile
prompts; it *only* affects the relatively small number of questions
asked by apt itself.

> I'm curious about the replies from those subscribers, who usually
> provide examples with the "assume-yes" option, when replying to other
> subscriber's requests.

I am not such a person, but for all the reasons above this line of
enquiry is a red herring with regard to the OP's situation.

-- 
Colin Watson                                       [cjwatson at ubuntu.com]