nixos/lib: systemd definition files function

Add a re-usable function that converts an attrset to a directory
containing systemd definition files.

nixos/lib/systemd-lib.nix

@@ -443,4 +443,21 @@ in rec {
           ${attrsToSection def.sliceConfig}
         '';
     };
+
+  # Create a directory that contains systemd definition files from an attrset
+  # that contains the file names as keys and the content as values. The values
+  # in that attrset are determined by the supplied format.
+  definitions = directoryName: format: definitionAttrs:
+    let
+      listOfDefinitions = lib.mapAttrsToList
+        (name: format.generate "${name}.conf")
+        definitionAttrs;
+    in
+    pkgs.runCommand directoryName { } ''
+      mkdir -p $out
+      ${(lib.concatStringsSep "\n"
+        (map (pkg: "cp ${pkg} $out/${pkg.name}") listOfDefinitions)
+      )}
+    '';
+
 }

nixos/modules/system/boot/systemd/repart.nix

@@ -1,28 +1,15 @@
-{ config, pkgs, lib, utils, ... }:
+{ config, lib, pkgs, utils, ... }:
 
 let
   cfg = config.systemd.repart;
   initrdCfg = config.boot.initrd.systemd.repart;
 
-  writeDefinition = name: partitionConfig: pkgs.writeText
-    "${name}.conf"
-    (lib.generators.toINI { } { Partition = partitionConfig; });
+  format = pkgs.formats.ini { };
 
-  listOfDefinitions = lib.mapAttrsToList
-    writeDefinition
-    (lib.filterAttrs (k: _: !(lib.hasPrefix "_" k)) cfg.partitions);
-
-  # Create a directory in the store that contains a copy of all definition
-  # files. This is then passed to systemd-repart in the initrd so it can access
-  # the definition files after the sysroot has been mounted but before
-  # activation. This needs a hard copy of the files and not just symlinks
-  # because otherwise the files do not show up in the sysroot.
-  definitionsDirectory = pkgs.runCommand "systemd-repart-definitions" { } ''
-    mkdir -p $out
-    ${(lib.concatStringsSep "\n"
-      (map (pkg: "cp ${pkg} $out/${pkg.name}") listOfDefinitions)
-    )}
-  '';
+  definitionsDirectory = utils.systemdUtils.lib.definitions
+    "repart.d"
+    format
+    (lib.mapAttrs (_n: v: { Partition = v; }) cfg.partitions);
 in
 {
   options = {

nixos/modules/system/boot/systemd/sysupdate.nix

@@ -5,16 +5,10 @@ let
 
   format = pkgs.formats.ini { };
 
-  listOfDefinitions = lib.mapAttrsToList
-    (name: format.generate "${name}.conf")
-    (lib.filterAttrs (k: _: !(lib.hasPrefix "_" k)) cfg.transfers);
-
-  definitionsDirectory = pkgs.runCommand "sysupdate.d" { } ''
-    mkdir -p $out
-    ${(lib.concatStringsSep "\n"
-      (map (pkg: "cp ${pkg} $out/${pkg.name}") listOfDefinitions)
-    )}
-  '';
+  definitionsDirectory = utils.systemdUtils.lib.definitions
+    "sysupdate.d"
+    format
+    cfg.transfers;
 in
 {
   options.systemd.sysupdate = {