Add extraFiles option

builder.nix

@@ -20,8 +20,10 @@
 , packagesArch ? null
 # Extra OpenWRT packages (can be prefixed with "-")
 , packages ? []
-# Include extra files
+# Directory of extra files to include
 , files ? null
+# Attrset of files to include
+, extraFiles ? { }
 # Which services in /etc/init.d/ should be disabled
 , disabledServices ? []
 # Add to output name
@@ -95,10 +97,23 @@ stdenv.mkDerivation {
       # copy files to avoid making etc read-only
       "cp -r --no-preserve=all ${files} files"
     }
+    ${lib.strings.concatStringsSep "\n" (
+      lib.attrsets.mapAttrsToList (
+        path: { source, text }: ''
+          mkdir -p $(dirname ./files/${path})
+          ${
+          if text != null then ''
+          cat << NIX_EOF > ./files/${path}
+          ${text}
+          NIX_EOF
+        '' else "cat < ${source} > ./files/${path}"}
+        ''
+      ) extraFiles)
+    }
     make image SHELL=${runtimeShell} \
       PROFILE="${profile}" \
       PACKAGES="${lib.concatStringsSep " " packages}" \
-      ${lib.optionalString (files != null)
+      ${lib.optionalString (files != null || extraFiles != { })
         ''FILES=./files''
       } \
       DISABLED_SERVICES="${lib.concatStringsSep " " disabledServices}" \

lib/modules/build.nix

@@ -4,7 +4,7 @@
   system.build.image = import ../../builder.nix {
     inherit pkgs;
     inherit (config.system) release target variant profile;
-    inherit (config) files;
+    inherit (config) files extraFiles;
     packages = config.packages.include
       ++ map (x: "-${x}") config.packages.exclude;
     disabledServices = config.services.disabled;

lib/modules/files.nix

@@ -1,8 +1,9 @@
 { lib, ... }:
 
 {
-  options.files = with lib;
+  options = with lib; {
-    mkOption {
+
+    files = mkOption {
       type = types.path;
       default = null;
       example = literalExample ''
@@ -18,4 +19,28 @@
       '';
       description = "Directory of files to included in images.";
     };
+
+    extraFiles = mkOption {
+      default = { };
+      description = ''
+        Set of files to build into the image.
+      '';
+      type = with types;
+        attrsOf (submodule {
+          options = {
+            source = mkOption {
+              default = null;
+              type = types.path;
+              description = "Path of the source file.";
+            };
+            text = mkOption {
+              default = null;
+              type = types.nullOr types.lines;
+              description = "Text of the file.";
+            };
+          };
+        });
+    };
+
+  };
 }