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…

Note: this command’s interface is based heavily around installables, which you may want to read about first (nix --help).

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 GNU Hello and print the resulting store path.

    # nix build nixpkgs#hello --print-out-paths
    /nix/store/v5sv61sszx301i0x6xysaqzla09nksnd-hello-2.10

•   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 --file 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.

•   --print-out-paths Print the resulting output paths

•   --profile path The profile to operate on.

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

•   --stdin Read installables from the standard input. No default installable applied.

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 Lix 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 Lix 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 Lix 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://channels.nixos.org/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.

•   --reference-lock-file flake-lock-path Read the given lock file instead of flake.lock within the top-level flake.

Logging-related options:

•   --debug Set the logging verbosity level to ‘debug’.

•   --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 Lix 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 that change the interpretation of installables:

•   --expr / -E 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. Implies --impure.

    Note

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