use backup VLAN and configure DDNS

nixos/ninurta/configuration.nix

@@ -76,6 +76,8 @@ in
   };
 
   dadada.ddns.domains = [ "backup1.dadada.li" ];
+  dadada.ddns.credentialsPath = config.age.secrets."ddns-credentials".path;
+  dadada.ddns.interface = "backup";
 
   dadada.borgServer = {
     enable = true;
@@ -118,6 +120,11 @@ in
     location = "/var/backup/postgresql";
   };
 
+  age.secrets."ddns-credentials" = {
+    file = "${secretsPath}/ddns-credentials.age";
+    mode = "400";
+  };
+
   age.secrets."ninurta-backup-passphrase" = {
     file = "${secretsPath}/ninurta-backup-passphrase.age";
     mode = "400";
@@ -241,6 +248,10 @@ in
         matchConfig.Name = "enp*";
         linkConfig.MACAddressPolicy = "persistent";
       };
+      "20-backup" = {
+        matchConfig.Name = "backup";
+        linkConfig.MACAddressPolicy = "persistent";
+      };
     };
     networks = {
       "10-wlan" = {
@@ -256,6 +267,11 @@ in
         networkConfig.DHCP = "ipv4";
         linkConfig.RequiredForOnline = "routable";
       };
+      "20-backup" = {
+        matchConfig.Name = "backup";
+        networkConfig.DHCP = "ipv4";
+        linkConfig.RequiredForOnline = false;
+      };
       "10-hydra" = {
         matchConfig.Name = "hydra";
         address = [ "10.3.3.3/24" ];
@@ -316,6 +332,13 @@ in
           };
         }];
       };
+      "20-backup" = {
+        netdevConfig = {
+          Name = "backup";
+          Kind = "vlan";
+        };
+        vlanConfig.Id = 13;
+      };
     };
   };