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Bug#1110883: release-notes: mDNS resolution in systemd-resolved disabled by default, breaking existing setups



Hi all,

Thanks for the feedback. The point re: bringing up a second package is well-taken. I originally added that because the root cause for why mDNS support was disabled was to prefer Avahi, but I see how it can be confusing here. I also understand the confusion about mDNS, so I tried adding a line to illustrate the use cases where Debian admins may be affected. Hopefully it's helpful without being overly complex.

How does the following look:

For trixie, support for [mDNS](https://en.wikipedia.org/wiki/Multicast_DNS) in systemd-resolved has been disabled by default. This has been done to prevent conflicts for users who have both systemd-resolved and avahi-daemon installed.

If you rely on systemd-resolved for mDNS resolution of *.local DNS names, or for answering mDNS queries from other hosts, you can mask the new drop-in config file so that mDNS support in systemd-resolved remains enabled. To do so, execute the following commands as root prior to upgrading systemd-resolved:

       mkdir -p /etc/systemd/resolved.conf.d/
       touch /etc/systemd/resolved.conf.d/00-disable-mdns.conf

Best,
Colin

On Sat, Aug 16, 2025 at 12:47 PM Chris Hofstaedtler <zeha@debian.org> wrote:
On Fri, Aug 15, 2025 at 10:56:20PM +0100, Richard Lewis wrote:
> On Tue, 12 Aug 2025 at 15:27, Colin Crawford <colin.j.crawford@gmail.com> wrote:
> > Thanks for the quick reply. I'm not a developer, so I'm afraid I don't know what an MR is or how to submit a patch. However, I've taken the text of the relevant NEWS item from the systemd-resolved package as a starting point for the text below. Please let me know if this draft is useful:
> >
> > For trixie, mDNS support is now globally disabled by default in systemd-resolved.
>
> can we explain what mDNS is - or link to somewhere that does. i have
> tried and failed to understand what it's purpose is before, without
> success.

that link can just be https://en.wikipedia.org/wiki/Multicast_DNS

Chris


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