Bug#1101532: systemd: unable to migrate to Testing because of removed packages

[Helmut Grohne]

Hi Noah,

Allow me to give background on the resolved matter without addressing
any other aspects of this. I've been managing the relevant ctte
discussion on that report.

On Mon, Mar 31, 2025 at 07:31:10PM -0400, Noah Meyerhans wrote:
> In the interest of trying to contribute potential solutions, one
> possibility that comes to mind is to use a generator to avoid
> conflicting with avahi.  If the generator determines that avahi is
> installed (I don't think it's possible to determine if it's actually
> enabled at that phase), we can disable MDNS support with a drop-in
> fragment in /run/systemd/resolved.conf.d/.  Have you considered such an
> approach?

A solution to this end was considered during the discussion phase. There
are various variants of it such as avahi-daemon installing the fragment.
The gist is the same. Avahi should be the default implementation and
resolved should only act as a mDNS resolver when avahi does not.

The option did not make it to the ballot that was voted on. The rough
consensus reached was that having resolved disable its mDNS
functionality on installing Avahi or enable mDNS on uninstalling Avahi
would be more confusing to users than simply leaving mDNS disabled in
resolved while letting users opt back in by changing the configuration
file or dropping a fragment. The expectation is that few users would be
depending on mDNS as implemented by resolved, because it additionally
needs to be enabled per interface in networkd and no present component
would perform such entablement in Debian. In other words, using the mDNS
functionality already requires user changes. At that point we were back
at simply changing the default state aligning Debian's defaults with
Fedora and Ubuntu.

Do you actually see that behavior of having resolved automatically
disable mDNS when Avahi gets installed as better? Few spoke up for that
option during the discussion phase, so I'd be interested in reasons
still. Maybe we moved too quickly there? In any case, a decision has
been made. We may consider doing another decision if new information
emerges, but time is running out and I am not seeing that new
information just yet.

Helmut