diff --git a/krebs/2configs/nameserver.nix b/krebs/2configs/nameserver.nix
new file mode 100644
index 000000000..4b205a13d
--- /dev/null
+++ b/krebs/2configs/nameserver.nix
@@ -0,0 +1,150 @@
+{ config, lib, pkgs, ... }: let
+  acmeChallenge =
+    { domain
+    , nameserver
+    , adminEmail
+    , serial ? 0
+    , refresh ? 3600
+    , retry ? 900
+    , expire ? 604800
+    , minimum ? 180
+    }:
+    pkgs.writeText "${domain}.zone" /* bindzone */ ''
+      $TTL 60
+      @ IN SOA ${lib.concatStringsSep " " [
+        "${nameserver}."
+        "${lib.replaceStrings ["@"] ["."] adminEmail}."
+        (toString serial)
+        (toString refresh)
+        (toString retry)
+        (toString expire)
+        (toString minimum)
+      ]}
+      @ IN NS ${nameserver}.
+    '';
+in {
+  networking.firewall.allowedTCPPorts = [
+    53 # domain for AXFR
+  ];
+  networking.firewall.allowedUDPPorts = [
+    53 # domain
+  ];
+
+  krebs.systemd.services.knot.restartIfCredentialsChange = true;
+  systemd.services.knot.serviceConfig.LoadCredential = [
+    "keys.conf:/var/src/secrets/knot-keys.conf"
+  ];
+
+  services.knot = {
+    enable = true;
+    keyFiles = [
+      "/run/credentials/knot.service/keys.conf"
+    ];
+    extraConfig = /* yaml */ ''
+      server:
+        udp-max-payload: 4096
+        listen: [ 127.0.0.53@2, ${
+          lib.concatMapStringsSep ", "
+            (addr: "${addr}@53")
+            (
+              config.krebs.build.host.nets.internet.addrs or []
+              ++
+              # This is required for hosts at OCI because the default route
+              # provided by DHCP is using the private address.
+              config.krebs.build.host.nets.intranet.addrs or []
+            )
+        } ]
+
+      log:
+        - target: syslog
+          any: debug
+
+      remote:
+
+      acl:
+        - id: acme_acl
+          key: acme
+          action: update
+
+        - id: dane_acl
+          key: dane
+          action: update
+
+      mod-rrl:
+        - id: default
+          rate-limit: 200   # Allow 200 resp/s for each flow
+          slip: 2           # Every other response slips
+
+      policy:
+        - id: rsa2k
+          algorithm: rsasha256
+          ksk-size: 4096
+          zsk-size: 2048
+
+      template:
+        - id: default
+          global-module: mod-rrl/default
+          semantic-checks: on
+          zonefile-sync: -1
+          zonefile-load: difference-no-serial
+          journal-content: all
+
+      zone:
+        - domain: krebsco.de
+          file: ${pkgs.krebs.zones."krebsco.de"}
+          dnssec-signing: on
+          dnssec-policy: rsa2k
+          acl: dane_acl
+
+        - domain: _acme-challenge.krebsco.de
+          file: ${acmeChallenge {
+            domain = "_acme-challenge.krebsco.de";
+            nameserver = "ns1.krebsco.de";
+            adminEmail = "spam@krebsco.de";
+          }}
+          acl: acme_acl
+
+        - domain: r
+          file: ${pkgs.krebs.zones.r}
+
+        - domain: w
+          file: ${pkgs.krebs.zones.w}
+    '';
+  };
+
+  systemd.services."knsupdate-krebsco.de" = {
+    serviceConfig = {
+      Type = "oneshot";
+      SyslogIdentifier = "knsupdate-krebsco.de";
+      ExecStart = pkgs.writeDash "knsupdate-krebsco.de" /* sh */ ''
+        set -efu
+
+        mk_certificate_association_data() {
+          ${pkgs.openssl}/bin/openssl x509 -noout -fingerprint -sha256 < "$1" |
+          ${pkgs.coreutils}/bin/cut -d= -f2 |
+          ${pkgs.coreutils}/bin/tr -d :
+        }
+
+        certfile=/var/lib/acme/krebsco.de/cert.pem
+        certificate_association_data=$(mk_certificate_association_data "$certfile")
+        keyfile=/var/src/secrets/dane.tsig
+
+        script=$(${pkgs.coreutils}/bin/mktemp -t knsupdate.XXXXXXXX)
+        trap 'rm "$script"' EXIT
+        (
+          exec >"$script"
+          echo server krebsco.de.
+          echo zone krebsco.de.
+          echo origin krebsco.de.
+          echo add _25._tcp.ni 60 IN TLSA 3 0 1 $certificate_association_data
+          echo add _443._tcp.ni 60 IN TLSA 3 0 1 $certificate_association_data
+          echo show
+          echo send
+          echo answer
+          echo quit
+        )
+        ${pkgs.knot-dns}/bin/knsupdate -k "$keyfile" "$script"
+      '';
+    };
+  };
+}