Build `aarch64` Docker image on `amd64` machine

Help
1

I have

packages.dockerImageServerArm = pkgs.pkgsCross.aarch64-multiplatform.dockerTools.buildImage {
  ...
  architecture = "aarch64";

  copyToRoot = pkgs.pkgsCross.aarch64-multiplatform.buildEnv {
    ...
  };
};

This package is built successfully on my amd64 machine.

When I run this image on an aarch64 box (on Hetzner), I get exec format error.
Furthermore, docker run ... on my amd64 machine succeeds; instead of expected exec format error.

Am I missing a requirement here? Such as building the image with binfmt? GitHub - tonistiigi/binfmt: Cross-platform emulator collection distributed with Docker images.

docker image inspect shows the correct architecture, but that is merely the architecture label set above.

Thank you

2

The problem is pkgs itself is likely for x86_64-linux. You’ll need to handle whether or not the current system is aarch64-linux and only use pkgs, otherwise pkgsCross can be used.

1 Like
3

You’re correct, thank you. There was an additional call to pkgs that I had missed, earlier. This detail is specific to the library I am using, haskell-flake.

  basePackages = pkgs.pkgsCross.aarch64-multiplatform.haskellPackages;
  ...
  packages.dockerImageServerArm = pkgs.pkgsCross.aarch64-multiplatform.dockerTools.buildImage {
  ...
  architecture = "aarch64";

  copyToRoot = pkgs.pkgsCross.aarch64-multiplatform.buildEnv {
    ...
  };
};

It is clearly building a completely different set of dependencies, now.

Is it actually possible to cross-compile this aarch64 package on my x86-64 machine? Or do I need an aarch64 worker node?
I am looking at error:

Couldn't find a target code interpreter. Try with -fexternal-interpreter
4

I am piecing this together here:

and here: Cross-building for aarch64 with Nix on a non-NixOS (Fedora 39) machine won't use the cache - #7 by ElvishJerricco

5

The error Couldn't find a target code interpreter. Try with -fexternal-interpreter is actually unrelated to cross-compilation.

It is a TH Haskell error: GHC 9.8 TemplateHaskell doesn't work in pkgsStatic · Issue #275304 · NixOS/nixpkgs · GitHub

Thanks to the Nix Cross Compiling Matrix channel: You're invited to talk on Matrix