nix3-build(1)

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

Name
nix build - build a derivation or fetch a store path

Synopsis
nix build [option…] installables…

Examples

•   Build the default package from the flake in the current directory:

    # nix build

•   Build and run GNU Hello from the nixpkgs flake:

    # nix build nixpkgs#hello
    # ./result/bin/hello
    Hello, world!

•   Build GNU Hello and Cowsay, leaving two result symlinks:

    # nix build nixpkgs#hello nixpkgs#cowsay
    # ls -l result*
    lrwxrwxrwx 1 … result -> /nix/store/v5sv61sszx301i0x6xysaqzla09nksnd-hello-2.10
    lrwxrwxrwx 1 … result-1 -> /nix/store/rkfrm0z6x6jmi7d3gsmma4j53h15mg33-cowsay-3.03+dfsg2

•   Build a specific output:

    # nix build nixpkgs#glibc.dev
    # ls -ld ./result-dev
    lrwxrwxrwx 1 … ./result-dev -> /nix/store/dkm3gwl0xrx0wrw6zi5x3px3lpgjhlw4-glibc-2.32-dev

•   Build attribute build.x86_64-linux from (non-flake) Nix expression release.nix:

    # nix build -f release.nix build.x86_64-linux

•   Build a NixOS system configuration from a flake, and make a profile point to the result:

    # nix build --profile /nix/var/nix/profiles/system \
      ~/my-configurations#nixosConfigurations.machine.config.system.build.toplevel

    (This is essentially what nixos-rebuild does.)

•   Build an expression specified on the command line:

    # nix build --impure --expr \
      'with import <nixpkgs> {};
       runCommand "foo" {
         buildInputs = [ hello ];
       }
       "hello > $out"'
    # cat ./result
    Hello, world!

    Note that --impure is needed because we’re using <nixpkgs>, which relies on the $NIX_PATH environment variable.

•   Fetch a store path from the configured substituters, if it doesn’t already exist:

    # nix build /nix/store/rkfrm0z6x6jmi7d3gsmma4j53h15mg33-cowsay-3.03+dfsg2

Description
nix build builds the specified installables. Installables that resolve to derivations are built (or substituted if possible). Store path installables are substituted.

Unless --no-link is specified, after a successful build, it creates symlinks to the store paths of the installables. These symlinks have the prefix ./result by default; this can be overridden using the --out-link option. Each symlink has a suffix -<N>-<outname>, where N is the index of the installable (with the left-most installable having index 0), and outname is the symbolic derivation output name (e.g. bin, dev or lib). -<N> is omitted if N = 0, and -<outname> is omitted if outname = out (denoting the default output).

Options

•   --dry-run
    Show what this command would do without doing it.

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

•   --no-link
    Do not create symlinks to the build results.

•   --out-link / -o path
    Use path as prefix for the symlinks to the build results. It defaults to result.

•   --profile path
    The profile to update.

•   --rebuild
    Rebuild an already built package and compare the result to the existing store paths.

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.

•   --eval-store store-url
    The Nix store to use for evaluations.

•   --impure
    Allow access to mutable paths and repositories.

•   --include / -I path
    Add path to the list of locations used to look up <...> file names.

•   --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.

•   --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.

•   --update-input input-path
    Update a specific flake input (ignoring its previous entry in the lock file).

Options that change the interpretation of installables:

•   --derivation
    Operate on the store derivation rather than its outputs.

•   --expr expr
    Interpret installables as attribute paths relative to the Nix expression expr.

•   --file / -f file
    Interpret installables as attribute paths relative to the Nix expression stored in file. If file is the character -, then a Nix expression will be read from standard input.