Merge pull request #104271 from adisbladis/dockertools-cross

dockerTools.buildLayeredImage: Fix cross compilation

nixos/tests/docker-tools.nix

@@ -234,5 +234,17 @@ import ./make-test-python.nix ({ pkgs, ... }: {
             "docker run --rm file-in-store nix-store --verify --check-contents",
             "docker run --rm file-in-store |& grep 'some data'",
         )
+
+    with subtest("Ensure cross compiled image can be loaded and has correct arch."):
+        docker.succeed(
+            "docker load --input='${pkgs.dockerTools.examples.cross-aarch64}'",
+        )
+        assert (
+            docker.succeed(
+                "docker inspect ${pkgs.dockerTools.examples.cross-aarch64.imageName} "
+                + "| ${pkgs.jq}/bin/jq -r .[].Architecture"
+            ).strip()
+            == "arm64v8"
+        )
   '';
 })

pkgs/build-support/docker/default.nix

@@ -31,6 +31,7 @@
   writeScript,
   writeText,
   writePython3,
+  system,  # Note: This is the cross system we're compiling for
 }:
 
 # WARNING: this API is unstable and may be subject to backwards-incompatible changes in the future.
@@ -48,7 +49,7 @@ let
     # A user is required by nix
     # https://github.com/NixOS/nix/blob/9348f9291e5d9e4ba3c4347ea1b235640f54fd79/src/libutil/util.cc#L478
     export USER=nobody
-    ${nix}/bin/nix-store --load-db < ${closureInfo {rootPaths = contentsList;}}/registration
+    ${buildPackages.nix}/bin/nix-store --load-db < ${closureInfo {rootPaths = contentsList;}}/registration
 
     mkdir -p nix/var/nix/gcroots/docker/
     for i in ${lib.concatStringsSep " " contentsList}; do
@@ -56,6 +57,16 @@ let
     done;
   '';
 
+  # Map nixpkgs architecture to Docker notation
+  # Reference: https://github.com/docker-library/official-images#architectures-other-than-amd64
+  getArch = nixSystem: {
+    aarch64-linux = "arm64v8";
+    armv7l-linux = "arm32v7";
+    x86_64-linux = "amd64";
+    powerpc64le-linux = "ppc64le";
+    i686-linux = "i386";
+  }.${nixSystem} or "Can't map Nix system ${nixSystem} to Docker architecture notation. Please check that your input and your requested build are correct or update the mapping in Nixpkgs.";
+
 in
 rec {
 
@@ -72,7 +83,7 @@ rec {
     , imageDigest
     , sha256
     , os ? "linux"
-    , arch ? buildPackages.go.GOARCH
+    , arch ? getArch system
 
       # This is used to set name to the pulled image
     , finalImageName ? imageName
@@ -443,7 +454,7 @@ rec {
       runCommand "${name}.tar.gz" {
         inherit (stream) imageName;
         passthru = { inherit (stream) imageTag; };
-        buildInputs = [ pigz ];
+        nativeBuildInputs = [ pigz ];
       } "${stream} | pigz -nT > $out";
 
   # 1. extract the base image
@@ -488,7 +499,7 @@ rec {
       baseJson = let
           pure = writeText "${baseName}-config.json" (builtins.toJSON {
             inherit created config;
-            architecture = buildPackages.go.GOARCH;
+            architecture = getArch system;
             os = "linux";
           });
           impure = runCommand "${baseName}-config.json"
@@ -715,7 +726,7 @@ rec {
       streamScript = writePython3 "stream" {} ./stream_layered_image.py;
       baseJson = writeText "${name}-base.json" (builtins.toJSON {
          inherit config;
-         architecture = buildPackages.go.GOARCH;
+         architecture = getArch system;
          os = "linux";
       });
 
@@ -762,7 +773,7 @@ rec {
             else
               lib.head (lib.strings.splitString "-" (baseNameOf conf.outPath));
         paths = referencesByPopularity overallClosure;
-        buildInputs = [ jq ];
+        nativeBuildInputs = [ jq ];
       } ''
         ${if (tag == null) then ''
           outName="$(basename "$out")"
@@ -826,7 +837,7 @@ rec {
           # take images can know in advance how the image is supposed to be used.
           isExe = true;
         };
-        buildInputs = [ makeWrapper ];
+        nativeBuildInputs = [ makeWrapper ];
       } ''
         makeWrapper ${streamScript} $out --add-flags ${conf}
       '';

pkgs/build-support/docker/examples.nix

@@ -7,7 +7,7 @@
 #  $ nix-build '<nixpkgs>' -A dockerTools.examples.redis
 #  $ docker load < result
 
-{ pkgs, buildImage, pullImage, shadowSetup, buildImageWithNixDb }:
+{ pkgs, buildImage, pullImage, shadowSetup, buildImageWithNixDb, pkgsCross }:
 
 rec {
   # 1. basic example
@@ -407,4 +407,11 @@ rec {
       contents = [ pkgs.bash pkgs.coreutils ] ++ nonRootShadowSetup { uid = 999; user = "somebody"; };
     };
 
+  # basic example, with cross compilation
+  cross-aarch64 = pkgsCross.aarch64-multiplatform.dockerTools.buildImage {
+    name = "hello-cross";
+    tag = "latest";
+    contents = pkgsCross.aarch64-multiplatform.hello;
+  };
+
 }

pkgs/top-level/all-packages.nix

@@ -239,7 +239,7 @@ in
   grsync = callPackage ../applications/misc/grsync { };
 
   dockerTools = callPackage ../build-support/docker {
-    writePython3 = writers.writePython3;
+    writePython3 = buildPackages.writers.writePython3;
   };
 
   snapTools = callPackage ../build-support/snap { };