Derivation JSON Format


This JSON format is currently experimental and subject to change.

The JSON serialization of a derivations is a JSON object with the following fields:

  • name: The name of the derivation. This is used when calculating the store paths of the derivation's outputs.

  • outputs: Information about the output paths of the derivation. This is a JSON object with one member per output, where the key is the output name and the value is a JSON object with these fields:

    • path: The output path, if it is known in advanced. Otherwise, null.

    • method: For an output which will be [content addresed], a string representing the method of content addressing that is chosen. Valid method strings are:

      Otherwise, null.

    • hashAlgo: For an output which will be [content addresed], the name of the hash algorithm used. Valid algorithm strings are:

      • md5
      • sha1
      • sha256
      • sha512
    • hash: For fixed-output derivations, the expected content hash in base-16.


    "outputs": {
      "out": {
        "path": "/nix/store/2543j7c6jn75blc3drf4g5vhb1rhdq29-source",
        "method": "nar",
        "hashAlgo": "sha256",
        "hash": "6fc80dcc62179dbc12fc0b5881275898f93444833d21b89dfe5f7fbcbb1d0d62"
  • inputSrcs: A list of store paths on which this derivation depends.

  • inputDrvs: A JSON object specifying the derivations on which this derivation depends, and what outputs of those derivations.


    "inputDrvs": {
      "/nix/store/6lkh5yi7nlb7l6dr8fljlli5zfd9hq58-curl-7.73.0.drv": ["dev"],
      "/nix/store/fn3kgnfzl5dzym26j8g907gq3kbm8bfh-unzip-6.0.drv": ["out"]

    specifies that this derivation depends on the dev output of curl, and the out output of unzip.

  • system: The system type on which this derivation is to be built (e.g. x86_64-linux).

  • builder: The absolute path of the program to be executed to run the build. Typically this is the bash shell (e.g. /nix/store/r3j288vpmczbl500w6zz89gyfa4nr0b1-bash-4.4-p23/bin/bash).

  • args: The command-line arguments passed to the builder.

  • env: The environment passed to the builder.