1 files changed, 47 insertions, 0 deletions
diff --git a/tools/nixery/build-image/build-layers.nix b/tools/nixery/build-image/build-layers.nix
new file mode 100644
index 000000000000..8a8bfbe9edf1
--- /dev/null
+++ b/tools/nixery/build-image/build-layers.nix
@@ -0,0 +1,47 @@
+# Copyright 2019 Google LLC
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     https://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+{
+  # Description of the package set to be used (will be loaded by load-pkgs.nix)
+  srcType ? "nixpkgs",
+  srcArgs ? "nixos-19.03",
+  importArgs ? { },
+  # Path to load-pkgs.nix
+  loadPkgs ? ./load-pkgs.nix,
+  # Layers to assemble into tarballs
+  layers ? "{}"
+}:
+
+let
+  inherit (builtins) fromJSON mapAttrs toJSON;
+  inherit (pkgs) lib runCommand;
+
+  pkgs = import loadPkgs { inherit srcType srcArgs importArgs; };
+
+  # Given a list of store paths, create an image layer tarball with
+  # their contents.
+  pathsToLayer = paths: runCommand "layer.tar" {
+  } ''
+    tar --no-recursion -Prf "$out" \
+        --mtime="@$SOURCE_DATE_EPOCH" \
+        --owner=0 --group=0 /nix /nix/store
+
+    tar -Prpf "$out" --hard-dereference --sort=name \
+        --mtime="@$SOURCE_DATE_EPOCH" \
+        --owner=0 --group=0 ${lib.concatStringsSep " " paths}
+  '';
+
+
+  layerTarballs = mapAttrs (_: pathsToLayer ) (fromJSON layers);
+in writeText "layer-tarballs.json" (toJSON layerTarballs)