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

Name

nix flake prefetch - download the source tree denoted by a flake reference into the Nix store

Synopsis

nix flake prefetch [option...] flake-url

Examples

  • Download a tarball and unpack it:

    # nix flake prefetch https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.5.tar.xz
Downloaded 'https://cdn.kernel.org/pub/linux/kernel/v5.x/linux-5.10.5.tar.xz?narHash=sha256-3XYHZANT6AFBV0BqegkAZHbba6oeDkIUCDwbATLMhAY='
to '/nix/store/sl5vvk8mb4ma1sjyy03kwpvkz50hd22d-source' (hash
'sha256-3XYHZANT6AFBV0BqegkAZHbba6oeDkIUCDwbATLMhAY=').

  • Download the dwarffs flake (looked up in the flake registry):

    # nix flake prefetch dwarffs --json
{"hash":"sha256-VHg3MYVgQ12LeRSU2PSoDeKlSPD8PYYEFxxwkVVDRd0="
,"storePath":"/nix/store/hang3792qwdmm2n0d9nsrs5n6bsws6kv-source"}

Description

This command downloads the source tree denoted by flake reference flake-url. Note that this does not need to be a flake (i.e. it does not have to contain a flake.nix file).

Options

  • --json

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

Common evaluation options:

  • --arg name expr

    Pass the value expr 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 the Nix search path. The Nix search path is initialized from the colon-separated NIX_PATH environment variable, and is used to look up the location of Nix expressions using paths enclosed in angle brackets (i.e., <nixpkgs>).

    For instance, passing

    -I /home/eelco/Dev
-I /etc/nixos

    will cause Nix to look for paths relative to /home/eelco/Dev and /etc/nixos, in that order. This is equivalent to setting the NIX_PATH environment variable to

    /home/eelco/Dev:/etc/nixos

    It is also possible to match paths against a prefix. For example, passing

    -I nixpkgs=/home/eelco/Dev/nixpkgs-branch
-I /etc/nixos

    will cause Nix to search for <nixpkgs/path> in /home/eelco/Dev/nixpkgs-branch/path and /etc/nixos/nixpkgs/path.

    If a path in the Nix search path starts with http:// or https://, it is interpreted as the URL of a tarball that will be downloaded and unpacked to a temporary location. The tarball must consist of a single top-level directory. For example, passing

    -I nixpkgs=https://github.com/NixOS/nixpkgs/archive/master.tar.gz

    tells Nix to download and use the current contents of the master branch in the nixpkgs repository.

    The URLs of the tarballs from the official nixos.org channels (see the manual page for nix-channel) can be abbreviated as channel:<channel-name>. For instance, the following two flags are equivalent:

    -I nixpkgs=channel:nixos-21.05
-I nixpkgs=https://nixos.org/channels/nixos-21.05/nixexprs.tar.xz

    You can also fetch source trees using flake URLs and add them to the search path. For instance,

    -I nixpkgs=flake:nixpkgs

    specifies that the prefix nixpkgs shall refer to the source tree downloaded from the nixpkgs entry in the flake registry. Similarly,

    -I nixpkgs=flake:github:NixOS/nixpkgs/nixos-22.05

    makes <nixpkgs> refer to a particular branch of the NixOS/nixpkgs repository on GitHub.

  • --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. This option is deprecated; use --no-use-registries.

  • --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.

  • --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).

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.

Options to override configuration settings: