Buildmachines works, maybe ?

modules/system/default.nix

@@ -11,5 +11,4 @@
   ];
 
   networking.hostName = name;
-  deployment.tags = config.system.nixos.tags;
 }

modules/system/settings/colmena/default.nix

@@ -0,0 +1,7 @@
+{ config, ... }:
+{
+  deployment = {
+    allowLocalDeployment = true;
+    tags = config.system.nixos.tags;
+  };
+}

modules/system/settings/default.nix

@@ -1,6 +1,7 @@
 { ... }:
 {
   imports = [
+    ./colmena
     ./font
     ./locale
     ./logind

modules/system/settings/nix/cache/default.nix

@@ -0,0 +1,13 @@
+{ ... }:
+{
+  nix.settings = {
+    substituters = [
+      "https://colmena.cachix.org"
+      "https://nix-community.cachix.org"
+    ];
+    trusted-public-keys = [
+      "colmena.cachix.org-1:7BzpDnjjH8ki2CT3f6GdOk7QAzPOl+1t3LvTLXqYcSg="
+      "nix-community.cachix.org-1:mB9FSh9qf2dCimDSUo8Zy7bkq5CX+/rkCWyvRCYg3Fs="
+    ];
+  };
+}

modules/system/settings/nix/default.nix

@@ -1,21 +1,19 @@
 { pkgs, ... }:
 {
   imports = [
+    ./cache
     ./channels
     ./distributed
-    ./gc
+    ./maintenence
     ./unfree
   ];
 
   nix = {
     package = pkgs.lix;
-    settings = {
-      auto-optimise-store = true;
-      experimental-features = [
-        "nix-command"
-        "flakes"
-      ];
-    };
+    settings.experimental-features = [
+      "flakes"
+      "nix-command"
+    ];
   };
 
   # Use a newer implementation of nixos-rebuild

modules/system/settings/nix/distributed/default.nix

@@ -1,39 +1,59 @@
-{ nodes, ... }:
+{ config, lib, nodes, ... }:
 {
   nix = {
     buildMachines = with nodes; [
       {
-        hostName = midas.config.deployment.targetHost;
-        system = midas.config.nixpkgs.localSystem.system;
-        publicHostKey = "AAAAC3NzaC1lZDI1NTE5AAAAIFcFMvrx9/iUZ1mEubf+QF1i3LNTxFhaU/1zFSjdo0kK";
+        hostName = "midas";
+        system = midas.config.nixpkgs.hostPlatform.system;
+        supportedFeatures = midas.config.nix.settings.system-features;
+        publicHostKey = "c3NoLWVkMjU1MTkgQUFBQUMzTnphQzFsWkRJMU5URTVBQUFBSUZjRk12cng5L2lVWjFtRXViZitRRjFpM0xOVHhGaGFVLzF6RlNqZG8wa0sgcm9vdEBraXR0eQo=";
         protocol = "ssh-ng";
+        sshKey = "/root/.ssh/buildkey";
+        maxJobs = 8;
       }
       {
-        hostName = kitty.config.deployment.targetHost;
-        system = kitty.config.nixpkgs.localSystem.system;
-        publicHostKey = "AAAAC3NzaC1lZDI1NTE5AAAAIIrGmsya5DXKuXO6jNjUlrYHqk49KLzxM/60GXtLRLrL";
+        hostName = "kitty";
+        system = kitty.config.nixpkgs.hostPlatform.system;
+        supportedFeatures = kitty.config.nix.settings.system-features;
+        publicHostKey = "c3NoLWVkMjU1MTkgQUFBQUMzTnphQzFsWkRJMU5URTVBQUFBSUlyR21zeWE1RFhLdVhPNmpOalVscllIcWs0OUtMenhNLzYwR1h0TFJMckwgcm9vdEBraXR0eQo=";
         protocol = "ssh-ng";
+        sshKey = "/root/.ssh/buildkey";
+        maxJobs = 8;
       }
       {
-        hostName = detritus.config.deployment.targetHost;
-        system = detritus.config.nixpkgs.localSystem.system;
-        publicHostKey = "AAAAC3NzaC1lZDI1NTE5AAAAIN+GvLro4DVmlvmXcasU1gctIX9qct7mZtElpB735AoL";
+        hostName = "detritus";
+        system = detritus.config.nixpkgs.hostPlatform.system;
+        supportedFeatures = detritus.config.nix.settings.system-features;
+        publicHostKey = "c3NoLWVkMjU1MTkgQUFBQUMzTnphQzFsWkRJMU5URTVBQUFBSU4rR3ZMcm80RFZtbHZtWGNhc1UxZ2N0SVg5cWN0N21adEVscEI3MzVBb0wgcm9vdEBkZXRyaXR1cwo=";
         protocol = "ssh-ng";
+        sshKey = "/root/.ssh/buildkey";
+        maxJobs = 8;
       }
       {
-        hostName = elder.config.deployment.targetHost;
-        system = elder.config.nixpkgs.localSystem.system;
-        publicHostKey = "AAAAC3NzaC1lZDI1NTE5AAAAIFjmJ6bkuO57gp6GZDEfR1O7krdf5wiqrOBC5pzTDl91";
+        hostName = "elder";
+        system = elder.config.nixpkgs.hostPlatform.system;
+        supportedFeatures = elder.config.nix.settings.system-features;
+        publicHostKey = "c3NoLWVkMjU1MTkgQUFBQUMzTnphQzFsWkRJMU5URTVBQUFBSUZqbUo2Ymt1TzU3Z3A2R1pERWZSMU83a3JkZjV3aXFyT0JDNXB6VERsOTEgcm9vdEBlbGRlcgo=";
         protocol = "ssh-ng";
+        sshKey = "/root/.ssh/buildkey";
+        maxJobs = 8;
       }
       {
-        hostName = prophet.config.deployment.targetHost;
-        system = prophet.config.nixpkgs.localSystem.system;
-        publicHostKey = "AAAAC3NzaC1lZDI1NTE5AAAAICrp3Y/X2BRUENx+0GMTmB1VDA6SiwkGgdJMHSdMMepM";
+        hostName = "prophet";
+        system = prophet.config.nixpkgs.hostPlatform.system;
+        supportedFeatures = prophet.config.nix.settings.system-features;
+        publicHostKey = "c3NoLWVkMjU1MTkgQUFBQUMzTnphQzFsWkRJMU5URTVBQUFBSUNycDNZL1gyQlJVRU54KzBHTVRtQjFWREE2U2l3a0dnZEpNSFNkTU1lcE0gcm9vdEBwcm9waGV0Cg==";
         protocol = "ssh-ng";
+        sshKey = "/root/.ssh/buildkey";
+        maxJobs = 8;
       }
     ];
+
     distributedBuilds = true;
-    settings.trusted-users = [ "root" ];
+
+    settings = {
+      max-jobs = if builtins.elem "server" config.system.nixos.tags then "auto" else 0;
+      trusted-users = [ "root" ];
+    };
   };
 }

modules/system/settings/nix/gc/default.nix

@@ -1,8 +0,0 @@
-{ ... }:
-{
-  nix.gc = {
-    automatic = true;
-    dates = "weekly";
-    options = "--delete-older-than 7d";
-  };
-}

modules/system/settings/nix/maintenence/default.nix

@@ -0,0 +1,13 @@
+{ ... }:
+{
+  nix = let
+    common = {
+      automatic = true;
+      persistent = true;
+    };
+  in {
+    gc = common;
+    optimise = common;
+    settings.auto-optimise-store = true;
+  };
+}