Flatpak

Flatpak is a Linux application sandboxing and distribution framework.

This article extends the documentation in the NixOS manual.

Usage

Using this configuration, flatpak will be installed and ready to use globally for all users:

/etc/nixos/configuration.nix

services.flatpak.enable = true;

If you'd rather make Flatpak available to a specific user, add flatpak to that user's packages. To be able to install Flatpaks graphically, add the gnome-software package. The result will look something like this:

/etc/nixos/configuration.nix

  users.users."user" = {
    packages = with pkgs; [
      flatpak
      gnome-software
    ];
  };

After adding the desired solution to your configuration file, Flatpak will be installed, but it is not always added to your path directly, e.g. when you are using Sway.

To manually add it to the path while using the Greetd login manager and Sway, create a .profile file with an override for your XDG_DATA_DIRS path, e.g.:

.profile

export XDG_DATA_DIRS=$XDG_DATA_DIRS:/usr/share:/var/lib/flatpak/exports/share:$HOME/.local/share/flatpak/exports/share

This is also required when installing flatpak on a per-user basis.

To start using flatpaks, particularly for flatpak development:

$ flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
$ flatpak update
$ flatpak search bustle
$ flatpak install flathub org.freedesktop.Bustle
$ flatpak run org.freedesktop.Bustle

To automatically configure a flatpak repository for all users using the global configuration file, add this to your configuration.nix file.

/etc/nixos/configuration.nix

  systemd.services.flatpak-repo = {
    wantedBy = [ "multi-user.target" ];
    path = [ pkgs.flatpak ];
    script = ''
      flatpak remote-add --if-not-exists flathub https://flathub.org/repo/flathub.flatpakrepo
    '';
  };

Development

Build a Flatpak project

The following example builds a demo app of the libadwaita repository using flatpak-builder, installs it locally in the user space and runs it. First install flatpak and flatpak-builder on your system

/etc/nixos/configuration.nix

services.flatpak.enable = true;
environment.systemPackages = [ pkgs.flatpak-builder ];

Clone, build and run the example project.

$ flatpak remote-add --if-not-exists gnome-nightly https://nightly.gnome.org/gnome-nightly.flatpakrepo
$ flatpak install gnome-nightly org.gnome.Sdk org.gnome.Platform
$ git clone https://gitlab.gnome.org/GNOME/libadwaita.git
$ cd libadwaita
$ nix shell nixpkgs#appstream
$ flatpak-builder --disable-tests --user --install build demo/org.gnome.Adwaita1.Demo.json
$ flatpak run org.gnome.Adwaita1.Demo.json

Note that the gnome-nightly repository and the appstream dependency are especially required for this specific project and might be different for other Flatpak projects.

Tips and tricks

Emulate Flatpaks of different architecture

It is possible to install and run Flatpaks which were compiled for a different platform. In this example we start the application Metronome as aarch64 Flatpak on a x86_64 host:

flatpak install --user --arch=aarch64 flathub com.adrienplazas.Metronome
flatpak run --user com.adrienplazas.Metronome

To support emulation with Qemu, following Binfmt configuration is required.

Troubleshooting

Missing themes and cursors

If you have issues with cursors or themes in general, take a look at Fonts#Flatpak_applications_can't_find_system_fonts