Quick Start to Adding a Package
To add a package to Nixpkgs:
Checkout the Nixpkgs source tree:
$ git clone https://github.com/NixOS/nixpkgs
$ 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/pkgname,
while a web browser goes into
pkgs/applications/networking/browsers/pkgname.
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 Hello:
pkgs/applications/misc/hello/default.nix.
Trivial package, which specifies some meta
attributes which is good practice.
GNU cpio:
pkgs/tools/archivers/cpio/default.nix.
Also a simple package. The generic builder in stdenv
does everything for you. It has no dependencies beyond
stdenv.
GNU Multiple Precision arithmetic library (GMP):
pkgs/development/libraries/gmp/5.1.x.nix.
Also done by the generic builder, but has a dependency on
m4.
Pan, a GTK-based newsreader:
pkgs/applications/networking/newsreaders/pan/default.nix.
Has an optional dependency on gtkspell, which is
only built if spellCheck is true.
Apache HTTPD:
pkgs/servers/http/apache-httpd/2.4.nix.
A bunch of optional features, variable substitutions in the configure
flags, a post-install hook, and miscellaneous hackery.
Thunderbird:
pkgs/applications/networking/mailreaders/thunderbird/default.nix.
Lots of dependencies.
JDiskReport, a Java utility:
pkgs/tools/misc/jdiskreport/default.nix
(and the
builder).
Nixpkgs doesn’t have a decent stdenv for Java yet
so this is pretty ad-hoc.
XML::Simple, a Perl module:
pkgs/top-level/perl-packages.nix
(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:
pkgs/applications/misc/adobe-reader/default.nix.
Shows how binary-only packages can be supported. In particular the
builder
uses patchelf to set the RUNPATH and ELF interpreter
of the executables so that the right libraries are found at runtime.
Some notes:
All meta attributes are
optional, but it’s still a good idea to provide at least the
description, homepage and
license.
You can use nix-prefetch-url (or similar
nix-prefetch-git, etc) url to get the
SHA-256 hash of source distributions. There are similar commands as
nix-prefetch-git and
nix-prefetch-hg available in
nix-prefetch-scripts package.
A list of schemes for mirror:// URLs can be found in
pkgs/build-support/fetchurl/mirrors.nix.
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 expressions.
Add a call to the function defined in the previous step to
pkgs/top-level/all-packages.nix
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:
$ nix-build -A libfoo
where libfoo should be the variable name defined in the
previous step. You may want to add the flag 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 and open a pull request, or send a patch
to https://groups.google.com/forum/#!forum/nix-devel.