Merge pull request #201902 from ck3mp3r/dockertools-architecture-in-config-200725

Adding ability to set image architecture when creating OCI images using DockerTools

doc/builders/images/dockertools.section.md

···
 
 - `config` is used to specify the configuration of the containers that will be started off the built image in Docker. The available options are listed in the [Docker Image Specification v1.2.0](https://github.com/moby/moby/blob/master/image/spec/v1.2.md#image-json-field-descriptions).
 
+- `architecture` is _optional_ and used to specify the image architecture, this is useful for multi-architecture builds that don't need cross compiling. If not specified it will default to `hostPlatform`.
+
 - `diskSize` is used to specify the disk size of the VM used to build the image in megabytes. By default it's 1024 MiB.
 
 - `buildVMMemorySize` is used to specify the memory size of the VM to build the image in megabytes. By default it's 512 MiB.
···
     *Default:* `[]`
 
 `config` _optional_
+
+`architecture` is _optional_ and used to specify the image architecture, this is useful for multi-architecture builds that don't need cross compiling. If not specified it will default to `hostPlatform`.
 
 : Run-time configuration of the container. A full list of the options are available at in the [Docker Image Specification v1.2.0](https://github.com/moby/moby/blob/master/image/spec/v1.2.md#image-json-field-descriptions).
 

nixos/tests/docker-tools.nix

···
             "docker rmi layered-image-with-path",
         )
 
+    with subtest("Ensure correct architecture is present in manifests."):
+        docker.succeed("""
+            docker load --input='${examples.build-image-with-architecture}'
+            docker inspect build-image-with-architecture \
+              | ${pkgs.jq}/bin/jq -er '.[] | select(.Architecture=="arm64").Architecture'
+            docker rmi build-image-with-architecture
+        """)
+        docker.succeed("""
+            ${examples.layered-image-with-architecture} | docker load
+            docker inspect layered-image-with-architecture \
+              | ${pkgs.jq}/bin/jq -er '.[] | select(.Architecture=="arm64").Architecture'
+            docker rmi layered-image-with-architecture
+        """)
+
     with subtest("etc"):
         docker.succeed("${examples.etc} | docker load")
         docker.succeed("docker run --rm etc | grep localhost")

pkgs/build-support/docker/default.nix

···
   # Reference: https://github.com/opencontainers/image-spec/blob/master/config.md#properties
   # For the mapping from Nixpkgs system parameters to GOARCH, we can reuse the
   # mapping from the go package.
-  defaultArch = go.GOARCH;
+  defaultArchitecture = go.GOARCH;
 
 in
 rec {
···
     , imageDigest
     , sha256
     , os ? "linux"
-    , arch ? defaultArch
-
+    , # Image architecture, defaults to the architecture of the `hostPlatform` when unset
+      arch ? defaultArchitecture
       # This is used to set name to the pulled image
     , finalImageName ? imageName
       # This used to set a tag to the pulled image
···
       keepContentsDirlinks ? false
     , # Docker config; e.g. what command to run on the container.
       config ? null
+    , # Image architecture, defaults to the architecture of the `hostPlatform` when unset
+      architecture ? defaultArchitecture
     , # Optional bash script to run on the files prior to fixturizing the layer.
       extraCommands ? ""
     , uid ? 0
···
       baseJson =
         let
           pure = writeText "${baseName}-config.json" (builtins.toJSON {
-            inherit created config;
-            architecture = defaultArch;
+            inherit created config architecture;
             preferLocalBuild = true;
             os = "linux";
           });
···
       contents ? [ ]
     , # Docker config; e.g. what command to run on the container.
       config ? { }
+    , # Image architecture, defaults to the architecture of the `hostPlatform` when unset
+      architecture ? defaultArchitecture
     , # Time of creation of the image. Passing "now" will make the
       # created date be the time of building.
       created ? "1970-01-01T00:00:01Z"
···
 
         streamScript = writePython3 "stream" { } ./stream_layered_image.py;
         baseJson = writeText "${baseName}-base.json" (builtins.toJSON {
-          inherit config;
-          architecture = defaultArch;
+          inherit config architecture;
           os = "linux";
         });
 

pkgs/build-support/docker/examples.nix

···
     ];
 
     extraCommands = ''
-      mkdir -p tmp
+      mkdir -p tmp/nginx_client_body
 
       # nginx still tries to read this directory even if error_log
       # directive is specifying another file :/
···
   layered-image-with-path = pkgs.dockerTools.streamLayeredImage {
     name = "layered-image-with-path";
     tag = "latest";
+    contents = [ pkgs.bashInteractive ./test-dummy ];
+  };
+
+  build-image-with-architecture = buildImage {
+    name = "build-image-with-architecture";
+    tag = "latest";
+    architecture = "arm64";
+    # Not recommended. Use `buildEnv` between copy and packages to avoid file duplication.
+    copyToRoot = [ pkgs.bashInteractive ./test-dummy ];
+  };
+
+  layered-image-with-architecture = pkgs.dockerTools.streamLayeredImage {
+    name = "layered-image-with-architecture";
+    tag = "latest";
+    architecture = "arm64";
     contents = [ pkgs.bashInteractive ./test-dummy ];
   };