Add modules

modules/build/activation.nix

@@ -0,0 +1,112 @@
+# Licensed under GNU Lesser General Public License v3 or later, see COPYING.
+# Copyright (c) 2019 Alexander Sosedkin and other contributors, see AUTHORS.
+
+{ config, lib, pkgs, ... }:
+
+with lib;
+
+let
+  cfg = config.build;
+
+  # Programs that always should be available on the activation
+  # script's PATH.
+  activationBinPaths = lib.makeBinPath [
+    pkgs.bash
+    pkgs.coreutils
+    pkgs.findutils
+    pkgs.gnused
+    pkgs.ncurses          # For `tput`.
+    pkgs.nix
+  ];
+
+  activationCmds = concatStringsSep "\n" (
+    mapAttrsToList (name: value: ''
+      noteEcho "Activating ${name}"
+      ${value}
+    '') cfg.activation
+  );
+
+  activationScript = pkgs.writeScript "activation-script" ''
+    #!${pkgs.runtimeShell}
+
+    set -eu
+    set -o pipefail
+
+    cd $HOME
+
+    export PATH="${activationBinPaths}"
+
+    ${builtins.readFile ../lib-bash/color-echo.sh}
+    ${builtins.readFile ../lib-bash/activation-init.sh}
+
+    ${activationCmds}
+  '';
+in
+
+{
+
+  ###### interface
+
+  options = {
+
+    build = {
+      activation = mkOption {
+        default = {};
+        type = types.attrs;
+        description = ''
+          Activation scripts for the nix-on-droid environment.
+          </para><para>
+          Any script should respect the <varname>DRY_RUN</varname>
+          variable, if it is set then no actual action should be taken.
+          The variable <varname>DRY_RUN_CMD</varname> is set to
+          <code>echo</code> if dry run is enabled. Thus, many cases you
+          can use the idiom <code>$DRY_RUN_CMD rm -rf /</code>.
+        '';
+      };
+
+      activationPackage = mkOption {
+        type = types.package;
+        readOnly = true;
+        internal = true;
+        description = "Derivation with activation script.";
+      };
+
+      etc = mkOption {
+        type = types.package;
+        internal = true;
+        description = "Package containing /etc files.";
+      };
+    };
+
+  };
+
+
+  ###### implementation
+
+  config = {
+
+    build.activationPackage =
+      pkgs.runCommand
+        "nix-on-droid-generation"
+        {
+          preferLocalBuild = true;
+          allowSubstitutes = false;
+        }
+        ''
+          mkdir --parents $out/filesystem/{bin,usr/{bin,lib}}
+
+          cp ${activationScript} $out/activate
+
+          ln --symbolic ${config.build.etc}/etc $out/etc
+          ln --symbolic ${config.environment.path} $out/nix-on-droid-path
+
+          ln --symbolic ${config.environment.files.login} $out/filesystem/bin/login
+          ln --symbolic ${config.environment.files.loginInner} $out/filesystem/usr/lib/login-inner
+
+          ln --symbolic ${config.environment.binSh} $out/filesystem/bin/sh
+          ln --symbolic ${config.environment.usrBinEnv} $out/filesystem/usr/bin/env
+        '';
+
+  };
+
+}