Name

nix flake bake - bake a flake

Synopsis

nix flake bake [option…] flake-url

Examples

• Bake the patchelf flake into the directory ./patchelf-baked:

  # nix flake bake github:NixOS/patchelf --dest-dir ./patchelf-baked
  

  The baked flake can be used like any other flake:

  # nix flake show path:./patchelf-baked
  # nix build path:./patchelf-baked#patchelf
  

• Bake the outputs for all systems, not just the current one:

  # nix flake bake github:NixOS/patchelf --dest-dir ./patchelf-baked --all-systems
  

Description

This command evaluates the outputs of the flake specified by flake reference flake-url and writes a new, baked flake to the directory path (specified by --dest-dir). The baked flake provides the same outputs as the original flake, but they are pre-evaluated: every derivation is replaced by a baked derivation, that is, a derivation with the builder builtin:substitute that is never built but whose outputs are obtained by substitution from a binary cache. As a result, evaluating a baked flake is much faster than evaluating the original, since it does (almost) no evaluation.

The baked flake has no inputs, so it can be used without access to the inputs of the original flake. It provides its own flake schemas (in the schemas output) that reproduce the structure of the original flake’s outputs, so nix flake show and nix flake check work on it without needing the original flake’s schemas.

Derivation attributes in the baked flake have the same name, system, outPath, outputName, outputs and meta.mainProgram as in the original flake, so commands such as nix build and nix run behave the same. Their drvPath is different, however: it refers to the baked derivation rather than the original one. The outputs of a baked flake can also be used as inputs of other derivations, e.g. by another flake that has the baked flake as an input.

Building the outputs of a baked flake requires that their store paths can be substituted (or are already present in the Nix store). If a store path cannot be substituted, the build fails; Nix will not fall back to building the original derivation.

By default, only the outputs for the current system are baked. Use --all-systems to bake the outputs for all systems.

Limitations

• Only outputs that are recognised by the flake schemas are baked. Non-derivation outputs, such as overlays, nixosModules and templates, are omitted from the baked flake.

• Derivations whose output paths are not known at evaluation time cannot be baked. This includes content-addressed derivations and impure derivations. nix flake bake prints a warning for each such derivation and omits it from the baked flake.

• Outputs whose derivation is nested inside the output attribute (such as nixosConfigurations.<name>.config.system.build.toplevel) are baked at that nested attribute. Other attributes of the output are not included.

This command requires the baked-derivations experimental feature, both in the Nix CLI and in the Nix daemon.

Options

• --all-systems

  Bake the outputs for all systems, not just the current system.

• --default-flake-schemas flake-ref

  The URL of the flake providing default flake schema definitions.

• --dest-dir path

  Directory in which to write the baked flake.nix.

• --read-only

  Do not instantiate each evaluated derivation. This improves performance, but can cause errors when accessing store paths of derivations during evaluation.

Common evaluation options

• --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.

Common flake-related options

• --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). The input path must not be empty. 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.

Logging-related options

• --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.

Miscellaneous global options

• --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.