Building docker image with dockerTools.buildImage and Flake env

Help
1

Hi all,

I am trying to build a simple docker image inside the “nixpkgs/nixos” and “nixpkgs/cachix-flakes” images with flake from, but I run into some difficulties.

{
  description = "Simple Docker Flake project";

  inputs = {
    nixpkgs.url = "github:nixos/nixpkgs/nixos-unstable";
    flake-utils.url = "github:numtide/flake-utils";
  };

  outputs = { self, nixpkgs, flake-utils }:
    flake-utils.lib.eachDefaultSystem (system:
      let pkgs = nixpkgs.legacyPackages.${system};
      in {
        packages.hello = pkgs.dockerTools.buildImage {
          name = "hello";
          tag = "0.1.0";

          config = { Cmd = [ "${pkgs.hello}/bin/hello" ]; };

          created = "now";
        };

        devShells.default =
          pkgs.mkShell { buildInputs = with pkgs; [ bat vim ]; };
      });
}

When I run nix build .#hello command without using flake environment (direnv: use flake) everything works fine, but when I load flake environment and try to build docker image, I get the following error.

error: builder for
'/nix/store/kyfd16cspq8hrc0bjrpd846rkg213jxr-hello-config. json.drv' failed with exit code 1;
last 2 log lines:
> unpacking sources
- variable $src or $srcs should point to the source
For full logs, run 'nix log /nix/store/kyfd16cspq8hrcobjrpd846rkg213jxr-hello-config.json.drv'
error: 1 dependencies of derivation '/nix/store/r2502npbrcsvzips0px03d4xrv5k3i8-hello-config.ison.drv'failed to build
error: 1 dependencies of derivation '/nix/store/roza2pch58s573x615sfswrai60nav4x-docker-image-hello.tar.az.drv'failed to build

Can someone take a look at this and please tell me what I’m doing wrong?

The above Flake code works fine outside the docker environment.

2

I tried to reproduce this on NixOS unstable but I cannot help. It works on my system (as it does for you):

nix develop
nix build .\#hello

What do you mean with “I am trying to build a simple docker image inside the “nixpkgs/nixos” and “nixpkgs/cachix-flakes” images with flake from, but I run into some difficulties.”? Does this mean you trying to run this inside of container based on what image?

Please provide more details on how to reproduce this.

3

Pardon my clumsy instructions… here are the exact commands to reproduce the error.

docker run -it --name buildDockerImage -v /root/flake.nix:/root/flake.nix nixos/nix

cd /root && echo "use flake" > .envrc

echo "experimental-features = flakes nix-command" >> /etc/nix/nix.conf
nix profile install nixpkgs#direnv
direnv allow && eval "$(direnv export bash)"

nix build .#hello
4

It is unclear to me why this fails. It works fine if i omit direnv and simply do the build. I assume that something in the environment (from direnv) causes this.