Meta-attributes

Standard meta-attributes The following meta-attributes have a standard interpretation: description A short (one-line) description of the package. This is shown by nix-env -q --description and also on the Nixpkgs release pages. Don’t include a period at the end. Don’t include newline characters. Capitalise the first character. For brevity, don’t repeat the name of package — just describe what it does. Wrong: "libpng is a library that allows you to decode PNG images." Right: "A library for decoding PNG images" longDescription An arbitrarily long description of the package. homepage The package’s homepage. Example: http://www.gnu.org/software/hello/manual/ license The license for the package. One from attribute set defined in nixpkgs/lib/licenses.nix. Example: stdenv.lib.licenses.gpl3. maintainers A list of names and e-mail addresses of the maintainers of this Nix expression. If you would like to be a maintainer of a package, you may want to add yourself to nixpkgs/lib/maintainers.nix and write something like [ stdenv.lib.maintainers.alice stdenv.lib.maintainers.bob ]. priority The priority of the package, used by nix-env to resolve file name conflicts between packages. See the Nix manual page for nix-env for details. Example: "10" (a low-priority package). platforms The list of Nix platform types on which the package is supported. An example is: meta.platforms = stdenv.lib.platforms.linux; Attribute Set stdenv.lib.platforms in nixpkgs/lib/platforms.nix defines various common lists of platforms types. hydraPlatforms The list of Nix platform types for which the Hydra instance at hydra.nixos.org will build the package. (Hydra is the Nix-based continuous build system.) It defaults to the value of meta.platforms. Thus, the only reason to set meta.hydraPlatforms is if you want hydra.nixos.org to build the package on a subset of meta.platforms, or not at all, e.g. meta.platforms = stdenv.lib.platforms.linux; meta.hydraPlatforms = []; broken If set to true, the package is marked as “broken”, meaning that it won’t show up in nix-env -qa, and cannot be built or installed. Such packages should be removed from Nixpkgs eventually unless they are fixed.

Licenses This is just a first attempt at standardising the license attribute. The meta.license attribute must be one of the following: GPL GNU General Public License; version not specified. GPLv2 GNU General Public License, version 2. GPLv2+ GNU General Public License, version 2 or higher. GPLv3 GNU General Public License, version 3. GPLv3+ GNU General Public License, version 3 or higher. bsd Catch-all for licenses that are essentially similar to the original BSD license with the advertising clause removed, i.e. permissive non-copyleft free software licenses. This includes the X11 (“MIT”) License. perl5 The Perl 5 license (Artistic License, version 1 and GPL, version 1 or later). free Catch-all for free software licenses not listed above. free-copyleft Catch-all for free, copyleft software licenses not listed above. free-non-copyleft Catch-all for free, non-copyleft software licenses not listed above. unfree-redistributable Unfree package that can be redistributed in binary form. That is, it’s legal to redistribute the output of the derivation. This means that the package can be included in the Nixpkgs channel. Sometimes proprietary software can only be redistributed unmodified. Make sure the builder doesn’t actually modify the original binaries; otherwise we’re breaking the license. For instance, the NVIDIA X11 drivers can be redistributed unmodified, but our builder applies patchelf to make them work. Thus, its license is unfree and it cannot be included in the Nixpkgs channel. unfree Unfree package that cannot be redistributed. You can build it yourself, but you cannot redistribute the output of the derivation. Thus it cannot be included in the Nixpkgs channel. unfree-redistributable-firmware This package supplies unfree, redistributable firmware. This is a separate value from unfree-redistributable because not everybody cares whether firmware is free.