`nix builds.toml` command

NAME

nix-builds.toml - catalog configuration for Nix expression builds

SYNOPSIS

The nix-builds.toml file declares external catalogs that are made available to Nix expression builds within a Flox environment. It lives at .flox/nix-builds.toml alongside the environment manifest.

DESCRIPTION

When a Flox environment uses Nix expression builds (packages defined as .nix files under .flox/pkgs/), those expressions can depend on packages provided by external catalogs. The nix-builds.toml file declares which catalogs are available and where they come from.

Running flox build update-catalogs resolves every catalog entry and writes the pinned result to .flox/nix-builds.lock. Both files should be committed to version control.

`version`

Required. The configuration format version. Currently the only supported value is 1.

version = 1

`[catalogs.<name>]`

Each section under catalogs declares a single catalog. The <name> becomes the key used to reference the catalog in Nix expressions: a package foo in catalog mycatalog is accessed as catalogs.mycatalog.foo.

A catalog can be specified in one of three forms.

Structured Nix source type

Provide a type field naming a Nix source type together with additional fields appropriate to that type:

[catalogs.mycatalog]
type = "git"
url = "https://github.com/org/repo"
ref = "main"

The supported types and their fields are documented in the Nix manual under Source types.

URL string

As a shorthand for the structured form, provide a single url field containing a Nix source reference:

[catalogs.mycatalog]
url = "git+https://github.com/org/repo"

The URL follows Nix source reference syntax and may include query parameters such as ?ref=<branch> or ?rev=<commit>.

FloxHub catalog

Set type to "floxhub" to pull packages from a catalog published on FloxHub:

[catalogs.mycatalog]
type = "floxhub"

The catalog name must match a catalog identifier registered on FloxHub.

Lockfile

Running flox build update-catalogs produces .flox/nix-builds.lock, a JSON file that pins every catalog to a specific resolved state. The lockfile is consumed at build time; it must be present and up to date before running flox build on packages that reference catalogs.

Using catalogs in Nix expressions

Nix expressions under .flox/pkgs/ receive a catalogs argument. Each catalog declared in nix-builds.toml appears as an attribute set keyed by <name>:

## .flox/pkgs/hello.nix
{ catalogs }:
catalogs.mycatalog.some-package

EXAMPLES

Declare a Git catalog

version = 1

[catalogs.mylib]
url = "git+https://github.com/org/mylib"

Declare a catalog with a pinned branch

version = 1

[catalogs.mylib]
type = "git"
url = "https://github.com/org/mylib"
ref = "release-2.0"

Declare a FloxHub catalog

version = 1

[catalogs.myorg]
type = "floxhub"

Use a catalog in a package expression

## .flox/pkgs/app.nix
{ catalogs }:
catalogs.myorg.build-tool

nix builds.toml command