···
<title>Adding Custom Packages</title>
It’s possible that a package you need is not available in NixOS. In
+
that case, you can do two things. Either you can package it with
+
Nix, or you can try to use prebuilt packages from upstream. Due to
+
the peculiarities of NixOS, it is important to note that building
+
software from source is often easier than using pre-built
+
<section xml:id="sec-custom-packages-nix">
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<title>Building with Nix</title>
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This can be done either in-tree or out-of-tree. For an in-tree
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build, you can clone the Nixpkgs repository, add the package to
+
your clone, and (optionally) submit a patch or pull request to
+
have it accepted into the main Nixpkgs repository. This is
+
described in detail in the
+
<link xlink:href="https://nixos.org/nixpkgs/manual">Nixpkgs
+
manual</link>. In short, you clone Nixpkgs:
$ git clone https://github.com/NixOS/nixpkgs
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Then you write and test the package as described in the Nixpkgs
+
manual. Finally, you add it to
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<xref linkend="opt-environment.systemPackages" />, e.g.
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<programlisting language="bash">
environment.systemPackages = [ pkgs.my-package ];
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and you run <literal>nixos-rebuild</literal>, specifying your own
# nixos-rebuild switch -I nixpkgs=/path/to/my/nixpkgs
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The second possibility is to add the package outside of the
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Nixpkgs tree. For instance, here is how you specify a build of the
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<link xlink:href="https://www.gnu.org/software/hello/">GNU
+
Hello</link> package directly in
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<literal>configuration.nix</literal>:
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<programlisting language="bash">
environment.systemPackages =
my-hello = with pkgs; stdenv.mkDerivation rec {
···
+
Of course, you can also move the definition of
+
<literal>my-hello</literal> into a separate Nix expression, e.g.
+
<programlisting language="bash">
environment.systemPackages = [ (import ./my-hello.nix) ];
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where <literal>my-hello.nix</literal> contains:
+
<programlisting language="bash">
with import <nixpkgs> {}; # bring all of Nixpkgs into scope
stdenv.mkDerivation rec {
···
+
This allows testing the package easily:
+
<section xml:id="sec-custom-packages-prebuilt">
+
<title>Using pre-built executables</title>
+
Most pre-built executables will not work on NixOS. There are two
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notable exceptions: flatpaks and AppImages. For flatpaks see the
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<link linkend="module-services-flatpak">dedicated section</link>.
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AppImages will not run <quote>as-is</quote> on NixOS. First you
+
need to install <literal>appimage-run</literal>: add to
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<literal>/etc/nixos/configuration.nix</literal>
+
<programlisting language="bash">
+
environment.systemPackages = [ pkgs.appimage-run ];
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Then instead of running the AppImage <quote>as-is</quote>, run
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<literal>appimage-run foo.appimage</literal>.
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To make other pre-built executables work on NixOS, you need to
+
package them with Nix and special helpers like
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<literal>autoPatchelfHook</literal> or
+
<literal>buildFHSUserEnv</literal>. See the
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<link xlink:href="https://nixos.org/nixpkgs/manual">Nixpkgs
+
manual</link> for details. This is complex and often doing a
+
source build is easier.