push sheeet

nixos/modules/system/activation/activatable-system.nix

@@ -0,0 +1,87 @@
+{
+  options,
+  config,
+  lib,
+  pkgs,
+  ...
+}:
+
+let
+  inherit (lib)
+    mkOption
+    types
+    ;
+
+  systemBuilderArgs = {
+    activationScript = config.system.activationScripts.script;
+    dryActivationScript = config.system.dryActivationScript;
+  };
+
+in
+{
+  options = {
+    system.activatable = mkOption {
+      type = types.bool;
+      default = true;
+      description = ''
+        Whether to add the activation script to the system profile.
+
+        The default, to have the script available all the time, is what we normally
+        do, but for image based systems, this may not be needed or not be desirable.
+      '';
+    };
+    system.activatableSystemBuilderCommands = options.system.systemBuilderCommands // {
+      description = ''
+        Like `system.systemBuilderCommands`, but only for the commands that are
+        needed *both* when the system is activatable and when it isn't.
+
+        Disclaimer: This option might go away in the future. It might be
+        superseded by separating switch-to-configuration into a separate script
+        which will make this option superfluous. See
+        https://github.com/NixOS/nixpkgs/pull/263462#discussion_r1373104845 for
+        a discussion.
+      '';
+    };
+    system.build.separateActivationScript = mkOption {
+      type = types.package;
+      description = ''
+        A separate activation script package that's not part of the system profile.
+
+        This is useful for configurations where `system.activatable` is `false`.
+        Otherwise, you can just use `system.build.toplevel`.
+      '';
+    };
+  };
+  config = {
+    system.activatableSystemBuilderCommands = ''
+      echo "$activationScript" > $out/activate
+      echo "$dryActivationScript" > $out/dry-activate
+      substituteInPlace $out/activate --subst-var-by out ''${!toplevelVar}
+      substituteInPlace $out/dry-activate --subst-var-by out ''${!toplevelVar}
+      chmod u+x $out/activate $out/dry-activate
+      unset activationScript dryActivationScript
+    '';
+
+    system.systemBuilderCommands = lib.mkIf config.system.activatable config.system.activatableSystemBuilderCommands;
+    system.systemBuilderArgs = lib.mkIf config.system.activatable (
+      systemBuilderArgs
+      // {
+        toplevelVar = "out";
+      }
+    );
+
+    system.build.separateActivationScript =
+      pkgs.runCommand "separate-activation-script"
+        (
+          systemBuilderArgs
+          // {
+            toplevelVar = "toplevel";
+            toplevel = config.system.build.toplevel;
+          }
+        )
+        ''
+          mkdir $out
+          ${config.system.activatableSystemBuilderCommands}
+        '';
+  };
+}