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systemd-resolved is a daemon that, among other things, acts as a DNS server by listening IP address 127.0.0.53 on the local loopback interface.

I would like to let the daemon listen to another interface. My use-case is to expose it to docker containers, so that docker containers share the DNS caching provided by systemd-resolved. I know how to configure the host as a DNS server for docker containers, but at least by default, systemd-resolved rejects these DNS queries because they are not coming from the loopback interface, but from the docker bridge interface.

With dnsmasq (a tool similar to systemd-resolved), I did this by adding listen-address=172.17.0.1 to the configuration file. Unfortunately, I couldn't find a systemd-resolved equivalent.

Since systemd-resolved is the default at least on Ubuntu 18.04, I would like a solution that works in this configuration.

Is there a way to configure which interface systemd-resolved listens on?

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    What is your use-case? I mean, why are you employing systemd-resolved as a stub resolver? There are any number of established, purpose-made alternatives, including but not limited to bind, dnsmasq, unbound, etc. Note that this is not a rant or mindless hate on the systemd suite. I'd just like to know what prompted you to pick this particular service. Is there any functionality the others don't offer? – Nubarke May 30 '18 at 15:42
  • My use case is to have docker that "just works" on my machine and on typical people's machine (e.g. my students, as I'm a teacher). I didn't pick systemd-resolved: my distro (Ubuntu) picked it for me when I upgraded (to 18.04). I can uninstall systemd-resolved and re-install dnsmasq (which I had before), but that's a rather intrusive solution, and in particular not a solution I'd recommend lightly to anyone (for example, I tried installing dnsmasq without uninstalling systemd-resolved. My package manager happily accepted and then my machine went berserk eating 100% CPU for nothing ...). – Matthieu Moy May 31 '18 at 8:04
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    Thanks for the reply. So I guess the question changes from "why did you pick systemd-resolved" to "why did the Ubuntu mantainers pick systemd-resolved". It seems clear that, at the very least, packages dnsmasq and systemd-resolved should have a breaks relationship. And again, why did the distro maintainers make that choice? Seems rather intrusive. – Nubarke Jun 1 '18 at 8:49
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Resolved is not intended nor designed for your use-case, but to provide services in the local loopback, thus the listen address is hardcoded.

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