View source for Nixpkgs/Building RPM DEB with nixpkgs

{{expansion}}

----

Please note that this page is under construction and the provided information is incomplete. Reach out to [https://github.com/matthiasbeyer matthiasbeyer] if this page was not updated in a long time.

----


== How it works ==

To build deb/rpm packages with nix/nixpkgs, it is critical to understand the process. Hence a short intro:

To build a deb or rpm package with nixpkgs, the build process needs a ''disk image'' which it then uses to boot a virtual machine (as in Qemu). Inside this virtual machine, the deb/rpm package is compiled from a ''tarball'' and then packaged using the respective tools for deb/rpm packaging.

Luckily, all that requirements are shipped inside nixpkgs itself.

== Preparation of the host machine ==

The host machine has to be prepared for the build process.

In the evaluation for this article, a CentOS 7 amd64 machine running in vmware was used.
On the machine, the nix package manager was installed via <code><nowiki>curl https://nixos.org/nix/install | sh</nowiki></code> as suggested on https://nixos.org/nix/ > "Get Nix".

The configuration file <code>/etc/nix/nix.conf</code> was edited for the following contents:
<syntaxHighlight>
sandbox = false
system-features = [ kvm nixos-test benchmark big-parallel ]
</syntaxHighlight>

This step might not be necessary on a NixOS installation.


== How to build a deb/rpm with nixpkgs ==

The following approach can be used to try out building a <code>.deb</code> package with nixpkgs:

# Clone the official nixpkgs repository into <code>~/nixpkgs</code>
# Add a file to the nixpkgs repository <code>./deb.nix</code> with the following contents:

(In this scenario, ncurses was built for testing the whole approach)

<syntaxHighlight lang=nix>
let
  pkgs = (import ./default.nix {});
  vm    = pkgs.vmTools.diskImageFuns.centos7x86_64 {};
  args = {
    diskImage = vm;
    diskImageFormat = "qcow2";
    src       = pkgs.ncurses.src;
    name      = "ncurses-deb";
    buildInputs = [];
    meta.description = "No descr";
  };
in pkgs.releaseTools.debBuild args
</syntaxHighlight>

and then this file was called: <code>nix-build ./deb.nix</code>.

This loads the relevant disk images from the channel mirror and spins up the Qemu VM to build the package.
The deb file (in this case, as we're building a deb with the expression from above) is located in ./result/debs/ after a successful build.