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.