Most packages come pre-built with binaries provided by the official Nix binary cache.

If you're modifying a package or using a package that's not built upstream, Nix will build it from source instead of downloading a binary.

To prevent packages from being built more than once, devenv provides seamless integration with binary caches hosted by Cachix.

Setup

Sign up on Cachix, create an organization and your first cache.

You don't need to install Cachix client, devenv will handle binary caching for you.

After that you'll need to set CACHIX_AUTH_TOKEN=XXX with either a personal auth token or a per cache token (that you can create in cache settings).

Pull

Configure your new cache:

devenv.nix

{
  cachix.pull = [ "mycache" ];
}

Note

devenv.cachix.org is added to the list of pull caches by default.

It mirrors the official NixOS cache and is designed to provide caching for the devenv-nixpkgs/rolling nixpkgs input.

Some languages and integrations may automatically add caches when enabled.

devenv.nix

{
  cachix.push = "mycache";
}

You'll likely not want every user to push to the cache.

It's usually convenient to enable pushing explicitly, for example as part of CI run:

$ echo '{ cachix.push = "mycache"; }' > devenv.local.nix

You can disable the integration by setting the following in devenv.nix:

devenv.nix

{
  cachix.enable = false;
}

Nix will continue to substitute binaries from any caches you may have configured externally, such as the official NixOS cache.