~/.config/nixpkgs/

config.nix

with import <nixpkgs> {};

{
  packageOverrides = pkgs: with pkgs; {
    nixUnstable = nixUnstable.overrideAttrs (attrs: {
      src = fetchFromGitHub {
        owner = "yorickvP";
        repo = "nix";
        rev = "dd7a21d40f8f649f2274a03e5cbdeb248796d5c8";
        sha256 = "0wwmxxqbqkrf9wgg6vif6djxmzbr5sfy2hisf5qdksn2j4817sml";
      };
    });
  };
}

out.sh

running test tests/export.sh... [FAIL]
    common.sh: line 88: unshare: command not found
    + clearStore
    + echo 'clearing store...'
    clearing store...
    + chmod -R +w /build/nix-test/store
    + rm -rf /build/nix-test/store
    + mkdir /build/nix-test/store
    + rm -rf /build/nix-test/var/nix
    + mkdir /build/nix-test/var/nix
    + nix-store --init
    + clearProfiles
    + profiles=/build/nix-test/var/nix/profiles
    + rm -rf /build/nix-test/var/nix/profiles
    ++ nix-build dependencies.nix --no-out-link
    these derivations will be built:
      /build/nix-test/store/1pjfggmwm6bvpybvxcivppgbd8l117yp-dependencies-input-1.drv
      /build/nix-test/store/yqf1fxxgc8rpchpcb4h2l17bbfr6gqbx-dependencies-input-2.drv
      /build/nix-test/store/4d5vxpyj8yj7i4f5mqkd1hfyj881v39i-dependencies.drv
    building '/build/nix-test/store/1pjfggmwm6bvpybvxcivppgbd8l117yp-dependencies-input-1.drv'...
    building '/build/nix-test/store/yqf1fxxgc8rpchpcb4h2l17bbfr6gqbx-dependencies-input-2.drv'...
    building '/build/nix-test/store/4d5vxpyj8yj7i4f5mqkd1hfyj881v39i-dependencies.drv'...
    FOO
    + outPath=/build/nix-test/store/r94kdgqxdy10qq1v9ngh7a6cvj70mg0b-dependencies
    + nix-store --export /build/nix-test/store/r94kdgqxdy10qq1v9ngh7a6cvj70mg0b-dependencies
    ++ nix-store -qR /build/nix-test/store/r94kdgqxdy10qq1v9ngh7a6cvj70mg0b-dependencies
    + nix-store --export /build/nix-test/store/qsy05mncqwsva433bvi0kvqvddjn6nfm-dependencies-input-2 /build/nix-test/store/r94kdgqxdy10qq1v9ngh7a6cvj70mg0b-dependencies
    + nix-store --export /build/nix-test/store/r94kdgqxdy10qq1v9ngh7a6cvj70mg0b-dependencies
    error: writing to file: No space left on device
    + clearStore
    + echo 'clearing store...'
    clearing store...
    + chmod -R +w /build/nix-test/store
    + rm -rf /build/nix-test/store
    + mkdir /build/nix-test/store
    + rm -rf /build/nix-test/var/nix
    + mkdir /build/nix-test/var/nix
    + nix-store --init
    + clearProfiles
    + profiles=/build/nix-test/var/nix/profiles
    + rm -rf /build/nix-test/var/nix/profiles
    + nix-store --import
    error: hash mismatch importing path '/build/nix-test/store/r94kdgqxdy10qq1v9ngh7a6cvj70mg0b-dependencies';
      wanted: sha256:19qxs9qnm32d4xn0p00gvkwvl4l6h736ibxx44fib7gz6dlij4fl
      got:    sha256:0dj63qi0pi2ndwm0c109v2rqrai6qidg49rgqkb227jz0ig3a8m6
    + clearStore
    + echo 'clearing store...'
    clearing store...
    + chmod -R +w /build/nix-test/store
    + rm -rf /build/nix-test/store
    + mkdir /build/nix-test/store
    + rm -rf /build/nix-test/var/nix
    + mkdir /build/nix-test/var/nix
    + nix-store --init
    + clearProfiles
    + profiles=/build/nix-test/var/nix/profiles
    + rm -rf /build/nix-test/var/nix/profiles
    + nix-store --import
    error: hash mismatch importing path '/build/nix-test/store/qsy05mncqwsva433bvi0kvqvddjn6nfm-dependencies-input-2';
      wanted: sha256:05a9fpb3skvj6b0ph1lbhv6vdqx66mp9mcppwkm2mq7csc2a2fn9
      got:    sha256:1vgbmjy9vigjplq5zmqkzx8r8qxqvd77r64lnwd88wzgjljzhq0y