2. Quick Start to Adding a Package
To add a package to Nixpkgs:
Checkout the Nixpkgs source tree:
$ git clone git://github.com/NixOS/nixpkgs.git
$ cd nixpkgs
Find a good place in the Nixpkgs tree to add the Nix expression for
your package. For instance, a library package typically goes into
pkgs/development/libraries/, while a web browser goes into
pkgs/applications/networking/browsers/. See ? for some hints on
the tree organisation. Create a directory for your package, e.g.
$ mkdir pkgs/development/libraries/libfoo
In the package directory, create a Nix expression — a piece of code
that describes how to build the package. In this case, it should be a
function that is called with the package dependencies as arguments,
and returns a build of the package in the Nix store. The expression
should usually be called default.nix.
$ emacs pkgs/development/libraries/libfoo/default.nix
$ git add pkgs/development/libraries/libfoo/default.nix
You can have a look at the existing Nix expressions under pkgs/
to see how it’s done. Here are some good ones:
- GNU cpio:
The simplest possible package. The generic builder in stdenv
does everything for you. It has no dependencies beyond stdenv.
- GNU Hello:
Also trivial, but it specifies some meta attributes which is
- GNU Multiple Precision arithmetic library (GMP):
Also done by the generic builder, but has a dependency on m4.
- Pan, a GTK-based newsreader:
Has an optional dependency on gtkspell, which is only built if
spellCheck is true.
- Apache HTTPD:
A bunch of optional features, variable substitutions in the
configure flags, a post-install hook, and miscellaneous hackery.
- BitTorrent (wxPython-based):
Uses an external build
which can be useful if you have lots of code that you don’t want
cluttering up the Nix expression. But external builders are mostly
Lots of dependencies.
- JDiskReport, a Java utility:
Nixpkgs doesn’t have a decent stdenv for Java yet so this is
- XML::Simple, a Perl module:
(search for the XMLSimple attribute). Most Perl modules are so
simple to build that they are defined directly in
perl-packages.nix; no need to make a separate file for them.
- Adobe Reader:
Shows how binary-only packages can be supported. In particular the
uses patchelf to set the RUNPATH and ELF interpreter of the
executables so that the right libraries are found at runtime.
The exact syntax and semantics of the Nix expression language,
including the built-in function, are described in the Nix manual in
the chapter on writing Nix
Add a call to the function defined in the previous step to
with some descriptive name for the variable, e.g. libfoo.
$ emacs pkgs/top-level/all-packages.nix
The attributes in that file are sorted by category (like “Development
/ Libraries”) that more-or-less correspond to the directory structure
of Nixpkgs, and then by attribute name.
To test whether the package builds, run the following command from
the root of the nixpkgs source tree:
where libfoo should be the variable name defined in the previous
step. You may want to add the flag -K to keep the temporary build
directory in case something fails. If the build succeeds, a symlink
./result to the package in the Nix store is created.
If you want to install the package into your profile (optional), do
$ nix-env -f . -iA libfoo
Optionally commit the new package, or send a patch to
If you want the TU Delft build farm to build binaries of the package
and make them available in the `nixpkgs
add it to