os/doc/outputs/pkgs.md
2021-09-02 11:37:21 +02:00

3.2 KiB

Packages

Similar to modules, the pkgs directory mirrors the upstream nixpkgs/pkgs, and for the same reason; if you ever want to upstream your package, it's as simple as dropping it into the nixpkgs/pkgs directory.

The only minor difference is that, instead of adding the callPackage call to all-packages.nix, you just add it the the default.nix in this directory, which is defined as a simple overlay.

All the packages are exported via packages.<system>.<pkg-name>, for all the supported systems listed in the package's meta.platforms attribute.

And, as usual, every package in the overlay is also available to any NixOS host.

Another convenient difference is that it is possible to use nvfetcher to keep packages up to date. This is best understood by the simple example below.

Example

It is possible to specify sources separately to keep them up to date semi automatically. The basic rules are specified in pkgs/sources.toml:

# nvfetcher.toml
[libinih]
src.github = "benhoyt/inih"
fetch.github = "benhoyt/inih"

After changes to this file as well as to update the packages specified in there run nvfetcher (for more details see nvfetcher).

The pkgs overlay is managed in pkgs/default.nix:

final: prev: {
  # keep sources first, this makes sources available to the pkgs
  sources = prev.callPackage (import ./_sources/generated.nix) { };

  # then, call packages with `final.callPackage`
  libinih = prev.callPackage ./development/libraries/libinih { };
}

Lastly the example package is in pkgs/development/libraries/libinih/default.nix:

{ stdenv, meson, ninja, lib, sources, ... }:
stdenv.mkDerivation {
  pname = "libinih";

  # version will resolve to the latest available on gitub
  inherit (sources.libinih) version src;

  buildInputs = [ meson ninja ];

  # ...
}

Migration from flake based approach

Previous to nvfetcher it was possible to manage sources via a pkgs/flake.nix, the main changes from there are that sources where in the attribute "srcs" (now "sources") and the contents of the sources where slightly different. In order to switch to the new system, rewrite pkgs/flake.nix to a pkgs/sources.toml file using the documentation of nvfetcher, add the line that calls the sources at the beginning of pkgs/default.nix, and accomodate the small changes in the packages as can be seen from the example.

The example package looked like:

pkgs/flake.nix:

{
  description = "Package sources";

  inputs = {
    libinih.url = "github:benhoyt/inih/r53";
    libinih.flake = false;
  };
}

pkgs/default.nix:

final: prev: {
  # then, call packages with `final.callPackage`
  libinih = prev.callPackage ./development/libraries/libinih { };
}

pkgs/development/libraries/libinih/default.nix:

{ stdenv, meson, ninja, lib, srcs, ... }:
let inherit (srcs) libinih; in
stdenv.mkDerivation {
  pname = "libinih";

  # version will resolve to 53, as specified in the flake.nix file
  inherit (libinih) version;

  src = libinih;

  buildInputs = [ meson ninja ];

  # ...
}