A while ago I wrote an entry about things that resolved wasn't for as of systemd 251 . One of those things was arbitrary mappings of (DNS) names to DNS servers, for example if you always wanted *.internal.example.org to query a special DNS server. Systemd-resolved didn't have a direct feature for this and attempting to attach your DNS names to DNS server mappings to a network interface could go wrong in various ways. Well, time marches on and as of systemd v258 this is no longer the state of affairs.

Systemd v258 introduces systemd.dns-delegate files, which allow you to map DNS names to DNS servers independently from network interfaces. The release notes describe this as:

A new DNS "delegate zone" concept has been introduced, which are additional lookup scopes (on top of the existing per-interface and the one global scope so far supported in resolved), which carry one or more DNS server addresses and a DNS search/routing domain. It allows routing requests to specific domains to specific servers. Delegate zones can be configured via drop-ins below /etc/systemd/dns-delegate.d/*.dns-delegate.

Since systemd v258 is very new I don't have any machines where I can actually try this out, but based on the systemd.dns-delegate documentation, you can use this both for domains that you merely want diverted to some DNS server and also domains that you also want on your search path. Per resolved.conf's Domains= documentation, the latter is 'Domains=example.org' (example.org will be one of the domains that resolved tries to find single-label hostnames in, a search domain ), and the former is 'Domains=~example.org' (where we merely send queries for everything under 'example.org' off to whatever DNS= you set, a route-only domain ).

(While resolved.conf's Domains= officially promises to check your search domains in the order you listed them, I believe this is strictly for a single 'Domains=' setting for a single interface. If you have multiple 'Domains=' settings, for example in a global resolved.conf, a network interface, and now in a delegation, I think systemd-resolved makes no promises.)

Right now, these DNS server delegations can only be set through static files, not manipulated through resolvectl . I believe fiddling with them through resolvectl is on the roadmap, but for now I guess we get to restart resolved if we need to change things. In fact resolvectl doesn't expose anything to do with them, although I believe read-only information is available via D-Bus and maybe varlink.

Given the timing of systemd v258's release relative to Fedora releases, I probably won't be able to use this feature until Fedora 44 in the spring (Fedora 42 is current and Fedora 43 is imminent , which won't have systemd v258 given that v258 was released only a couple of weeks ago). My current systemd-resolved setup is okay (if it wasn't I'd be doing something else), but I can probably find uses for these delegations to improve it.