Add a nix_worker role for nix builders.

nix/configuration/roles/nix_worker/default.nix

@@ -0,0 +1,57 @@
+# MANUAL: Remember to set up root's ssh config with any necessary values. For example:
+
+# Host foo
+#   HostName ns1.fizz.buzz
+#   Port 65122
+#   User nixworker
+#   IdentitiesOnly yes
+#   IdentityFile /persist/manual/ssh/root/keys/id_ed25519
+
+# Host *
+#   Compression yes
+
+{
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+{
+  imports = [ ];
+
+  options.me = {
+    nix_worker.enable = lib.mkOption {
+      type = lib.types.bool;
+      default = false;
+      example = true;
+      description = "Whether this machine should be set up to function as a nix.buildMachines. This does not configure nix.buildMachines, but only does the necessary setup to get the machine ready/capable of being a nix.buildMachines.";
+    };
+  };
+
+  config = lib.mkIf config.me.nix_worker.enable (
+    lib.mkMerge [
+      {
+        nix.settings.trusted-users = [ "nixworker" ];
+
+        users.users.nixworker = {
+          isNormalUser = true;
+          createHome = true; # https://github.com/NixOS/nixpkgs/issues/6481
+          group = "nixworker";
+          # extraGroups = [ "wheel" ];
+          # Generate with `mkpasswd -m scrypt`
+          hashedPassword = "$7$CU..../....VXvNQ8za3wSGpdzGXNT50/$HcFtn/yvwPMCw4888BelpiAPLAxe/zU87fD.d/N6U48";
+          openssh.authorizedKeys.keys = [
+            # Normal keys:
+            "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIGu+k5lrirokdW5zVdRVBOqEOAvAPlIkG/MdJNc9g5ky"
+            "sk-ssh-ed25519@openssh.com AAAAGnNrLXNzaC1lZDI1NTE5QG9wZW5zc2guY29tAAAAIEI6mu6I5Jp+Ib0vJxapGHbEShZjyvzV8jz5DnzDrI39AAAABHNzaDo="
+            "sk-ssh-ed25519@openssh.com AAAAGnNrLXNzaC1lZDI1NTE5QG9wZW5zc2guY29tAAAAIAFNcSXwvy+brYTOGo56G93Ptuq2MmZsjvRWAfMqbmMLAAAABHNzaDo="
+            # Key for nix to connect:
+            "ssh-ed25519 AAAAC3NzaC1lZDI1NTE5AAAAIB/IlYTQ0M5pFN5tdoswh37CDl/gbULI3h+SsKXCansh talexander@odo"
+          ];
+        };
+        users.groups.nixworker = { };
+      }
+    ]
+  );
+}

nix/configuration/roles/ssh/files/ssh_config_root

@@ -1,7 +1,14 @@
 Host hydra
   HostName ns1.fizz.buzz
   Port 65122
-  User talexander
+  User nixworker
+  IdentitiesOnly yes
+  IdentityFile /persist/manual/ssh/root/keys/id_ed25519
+
+Host quark
+  HostName quark
+  Port 22
+  User nixworker
   IdentitiesOnly yes
   IdentityFile /persist/manual/ssh/root/keys/id_ed25519