nix3-flake-metadata(1) General Commands Manual nix3-flake-metadata(1)

Warning
This program is experimental and its interface is subject to change.

nix flake metadata - show flake metadata

nix flake metadata [option…] flake-url

•
Show what dwarffs resolves to:
# nix flake metadata dwarffs
Resolved URL:  github:edolstra/dwarffs
Locked URL:    github:edolstra/dwarffs/f691e2c991e75edb22836f1dbe632c40324215c5
Description:   A filesystem that fetches DWARF debug info from the Internet on demand
Path:          /nix/store/769s05vjydmc2lcf6b02az28wsa9ixh1-source
Revision:      f691e2c991e75edb22836f1dbe632c40324215c5
Last modified: 2021-01-21 15:41:26
Inputs:
├───nix: github:NixOS/nix/6254b1f5d298ff73127d7b0f0da48f142bdc753c
│   ├───lowdown-src: github:kristapsdz/lowdown/1705b4a26fbf065d9574dce47a94e8c7c79e052f
│   └───nixpkgs: github:NixOS/nixpkgs/ad0d20345219790533ebe06571f82ed6b034db31
└───nixpkgs follows input 'nix/nixpkgs'
•
Show information about dwarffs in JSON format:
# nix flake metadata dwarffs --json | jq .
{
"description": "A filesystem that fetches DWARF debug info from the Internet on demand",
"lastModified": 1597153508,
"locked": {
  "lastModified": 1597153508,
  "narHash": "sha256-VHg3MYVgQ12LeRSU2PSoDeKlSPD8PYYEFxxwkVVDRd0=",
  "owner": "edolstra",
  "repo": "dwarffs",
  "rev": "d181d714fd36eb06f4992a1997cd5601e26db8f5",
  "type": "github"
},
"locks": { ... },
"original": {
  "id": "dwarffs",
  "type": "indirect"
},
"originalUrl": "flake:dwarffs",
"path": "/nix/store/hang3792qwdmm2n0d9nsrs5n6bsws6kv-source",
"resolved": {
  "owner": "edolstra",
  "repo": "dwarffs",
  "type": "github"
},
"resolvedUrl": "github:edolstra/dwarffs",
"revision": "d181d714fd36eb06f4992a1997cd5601e26db8f5",
"url": "github:edolstra/dwarffs/d181d714fd36eb06f4992a1997cd5601e26db8f5"
}

This command shows information about the flake specified by the flake reference flake-url. It resolves the flake reference using the flake registry, fetches it, and prints some meta data. This includes:

  • Resolved URL: If flake-url is a flake identifier, then this is the flake reference that specifies its actual location, looked up in the flake registry.
  • Locked URL: A flake reference that contains a commit or content hash and thus uniquely identifies a specific flake version.
  • Description: A one-line description of the flake, taken from the description field in flake.nix.
  • Path: The store path containing the source code of the flake.
  • Revision: The Git or Mercurial commit hash of the locked flake.
  • Revisions: The number of ancestors of the Git or Mercurial commit of the locked flake. Note that this is not available for github flakes.
  • Last modified: For Git or Mercurial flakes, this is the commit time of the commit of the locked flake; for tarball flakes, it’s the most recent timestamp of any file inside the tarball.
  • Inputs: The flake inputs with their corresponding lock file entries.

With --json, the output is a JSON object with the following fields:

  • original and originalUrl: The flake reference specified by the user (flake-url) in attribute set and URL representation.
  • resolved and resolvedUrl: The resolved flake reference (see above) in attribute set and URL representation.
  • locked and lockedUrl: The locked flake reference (see above) in attribute set and URL representation.
  • description: See Description above.
  • path: See Path above.
  • revision: See Revision above.
  • revCount: See Revisions above.
  • lastModified: See Last modified above.
  • locks: The contents of flake.lock.

•
--json
Produce output in JSON format, suitable for consumption by another program.

•
--arg name expr
Pass the value expr as the argument name to Nix functions.
•
--arg-from-file name path
Pass the contents of file path as the argument name to Nix functions.
•
--arg-from-stdin name
Pass the contents of stdin as the argument name to Nix functions.
•
--argstr name string
Pass the string string as the argument name to Nix functions.
•
--debugger
Start an interactive environment if evaluation fails.
•
--eval-store store-url
The URL of the Nix store to use for evaluation, i.e. to store derivations (.drv files) and inputs referenced by them.
•
--impure
Allow access to mutable paths and repositories.
•
--include / -I path
Add path to search path entries used to resolve lookup paths
This option may be given multiple times.
Paths added through -I take precedence over the nix-path configuration setting and the NIX_PATH environment variable.
•
--override-flake original-ref resolved-ref
Override the flake registries, redirecting original-ref to resolved-ref.
•
--commit-lock-file
Commit changes to the flake’s lock file.
•
--inputs-from flake-url
Use the inputs of the specified flake as registry entries.
•
--no-registries
Don’t allow lookups in the flake registries.
DEPRECATED
Use --no-use-registries instead.
•
--no-update-lock-file
Do not allow any updates to the flake’s lock file.
•
--no-write-lock-file
Do not write the flake’s newly generated lock file.
•
--output-lock-file flake-lock-path
Write the given lock file instead of flake.lock within the top-level flake.
•
--override-input input-path flake-url
Override a specific flake input (e.g. dwarffs/nixpkgs). This implies --no-write-lock-file.
•
--recreate-lock-file
Recreate the flake’s lock file from scratch.
DEPRECATED
Use nix flake update instead.
•
--reference-lock-file flake-lock-path
Read the given lock file instead of flake.lock within the top-level flake.
•
--update-input input-path
Update a specific flake input (ignoring its previous entry in the lock file).
DEPRECATED
Use nix flake update instead.
•
--debug
Set the logging verbosity level to ‘debug’.
•
--log-format format
Set the format of log output; one of raw, internal-json, bar or bar-with-logs.
•
--print-build-logs / -L
Print full build logs on standard error.
•
--quiet
Decrease the logging verbosity level.
•
--verbose / -v
Increase the logging verbosity level.

•
--help
Show usage information.
•
--offline
Disable substituters and consider all previously downloaded files up-to-date.
•
--option name value
Set the Nix configuration setting name to value (overriding nix.conf).
•
--refresh
Consider all previously downloaded files out-of-date.
•
--repair
During evaluation, rewrite missing or corrupted files in the Nix store. During building, rebuild missing or corrupted store paths.
•
--version
Show version information.

Note

See man nix.conf for overriding configuration settings with command line flags.