nix build results in "failed to create symbolic link"

[SebastianStork]

I followed the instructions for the "Using as a nixos-module" method. My configuration can be found here.

When I run nix build .#nixosConfigurations.installer.config.formats.iso I get this error:

error: builder for '/nix/store/0acylkkqsd9q36gzdqwibc1337jhwfhd-NixOS.iso.drv' failed with exit code 1;
       last 10 log lines:
       > sourcing setup hook '/nix/store/fyaryjvghbkpfnsyw97hb3lyb37s1pd6-move-lib64.sh'
       > sourcing setup hook '/nix/store/kd4xwxjpjxi71jkm6ka0np72if9rm3y0-move-sbin.sh'
       > sourcing setup hook '/nix/store/pag6l61paj1dc9sv15l7bm5c17xn5kyk-move-systemd-user-units.sh'
       > sourcing setup hook '/nix/store/jivxp510zxakaaic7qkrb7v1dd2rdbw9-multiple-outputs.sh'
       > sourcing setup hook '/nix/store/ilaf1w22bxi6jsi45alhmvvdgy4ly3zs-patch-shebangs.sh'
       > sourcing setup hook '/nix/store/cickvswrvann041nqxb0rxilc46svw1n-prune-libtool-files.sh'
       > sourcing setup hook '/nix/store/xyff06pkhki3qy1ls77w10s0v79c9il0-reproducible-builds.sh'
       > sourcing setup hook '/nix/store/aazf105snicrlvyzzbdj85sx4179rpfp-set-source-date-epoch-to-latest.sh'
       > sourcing setup hook '/nix/store/gps9qrh99j7g02840wv5x78ykmz30byp-strip.sh'
       > ln: failed to create symbolic link '/nix/store/2yx7pj2gy89fj1m6vcvcd0j358hrd7bs-NixOS.iso' -> '': No such file or directory
       For full logs, run 'nix log /nix/store/0acylkkqsd9q36gzdqwibc1337jhwfhd-NixOS.iso.

The same happens when I append -o result to specify the symlink location.

Is this intended behavior? I couldn't find any other mention of this anywhere. Any help is appreciated.

[Mic92]

Could be a bug or regression.
Check nix show-derivation /nix/store/0acylkkqsd9q36gzdqwibc1337jhwfhd-NixOS.iso.drv to get the build instructions for this.
I strongly suspect this command here fails and it returns an empty string:

nixos-generators/all-formats.nix

Line 36 in 1cb3dc2

target=$(find '${conf.config.system.build.${conf.config.formatAttr}}' -name '*${conf.config.fileExtension}' -xtype f -print -quit)

making this line fail:

nixos-generators/all-formats.nix

Line 37 in 1cb3dc2

ln -s "$target" "$out"

[SebastianStork]

Here is the output:

{
  "/nix/store/0acylkkqsd9q36gzdqwibc1337jhwfhd-NixOS.iso.drv": {
    "args": [
      "-e",
      "/nix/store/v6x3cs394jgqfbi0a42pam708flxaphh-default-builder.sh"
    ],
    "builder": "/nix/store/i1x9sidnvhhbbha2zhgpxkhpysw6ajmr-bash-5.2p26/bin/bash",
    "env": {
      "__structuredAttrs": "",
      "buildCommand": "set -efu\ntarget=$(find '/nix/store/2y2fq0q6ij8c86mv10d6vhqvi8fnd08y-NixOS' -name '*.iso' -xtype f -print -quit)\nln -s \"$target\" \"$out\"\n",
      "buildInputs": "",
      "builder": "/nix/store/i1x9sidnvhhbbha2zhgpxkhpysw6ajmr-bash-5.2p26/bin/bash",
      "cmakeFlags": "",
      "configureFlags": "",
      "depsBuildBuild": "",
      "depsBuildBuildPropagated": "",
      "depsBuildTarget": "",
      "depsBuildTargetPropagated": "",
      "depsHostHost": "",
      "depsHostHostPropagated": "",
      "depsTargetTarget": "",
      "depsTargetTargetPropagated": "",
      "doCheck": "",
      "doInstallCheck": "",
      "enableParallelBuilding": "1",
      "enableParallelChecking": "1",
      "enableParallelInstalling": "1",
      "mesonFlags": "",
      "name": "NixOS.iso",
      "nativeBuildInputs": "",
      "out": "/nix/store/2yx7pj2gy89fj1m6vcvcd0j358hrd7bs-NixOS.iso",
      "outputs": "out",
      "passAsFile": "buildCommand",
      "patches": "",
      "propagatedBuildInputs": "",
      "propagatedNativeBuildInputs": "",
      "stdenv": "/nix/store/6a7qxqcm33y3lwr1v55hpp5hg7akja92-stdenv-linux",
      "strictDeps": "",
      "system": "x86_64-linux"
    },
    "inputDrvs": {
      "/nix/store/0bjp0x3hysgy3hdvjcflmpy2al96jcl1-NixOS.drv": {
        "dynamicOutputs": {},
        "outputs": [
          "out"
        ]
      },
      "/nix/store/j5s66rbmbp025zdaj14g3hqjk83q00w2-stdenv-linux.drv": {
        "dynamicOutputs": {},
        "outputs": [
          "out"
        ]
      },
      "/nix/store/wzh01sawfkrvg2srg4jl8zprz1a347gy-bash-5.2p26.drv": {
        "dynamicOutputs": {},
        "outputs": [
          "out"
        ]
      }
    },
    "inputSrcs": [
      "/nix/store/v6x3cs394jgqfbi0a42pam708flxaphh-default-builder.sh"
    ],
    "name": "NixOS.iso",
    "outputs": {
      "out": {
        "path": "/nix/store/2yx7pj2gy89fj1m6vcvcd0j358hrd7bs-NixOS.iso"
      }
    },
    "system": "x86_64-linux"
  }
}

And I can confirm that find '/nix/store/2y2fq0q6ij8c86mv10d6vhqvi8fnd08y-NixOS' -name '*.iso' -xtype f -print -quit) returns an empty string.

[Mic92]

What's in /nix/store/2y2fq0q6ij8c86mv10d6vhqvi8fnd08y-NixOS if you run this command?

find /nix/store/2y2fq0q6ij8c86mv10d6vhqvi8fnd08y-NixOS

[SebastianStork]

/nix/store/2y2fq0q6ij8c86mv10d6vhqvi8fnd08y-NixOS
/nix/store/2y2fq0q6ij8c86mv10d6vhqvi8fnd08y-NixOS/iso
/nix/store/2y2fq0q6ij8c86mv10d6vhqvi8fnd08y-NixOS/iso/NixOS
/nix/store/2y2fq0q6ij8c86mv10d6vhqvi8fnd08y-NixOS/nix-support
/nix/store/2y2fq0q6ij8c86mv10d6vhqvi8fnd08y-NixOS/nix-support/system
/nix/store/2y2fq0q6ij8c86mv10d6vhqvi8fnd08y-NixOS/nix-support/hydra-build-products

That seems totally fine to me. I get the same result when I do nix run nixpkgs#nixos-generators -- --format iso --flake .#installer -o result.

[Mic92]

So /nix/store/2y2fq0q6ij8c86mv10d6vhqvi8fnd08y-NixOS/iso/NixOS is an iso file?

[SebastianStork]

That's right. I tested it and it works fine.