Skip to content
Back to top
View this page

# Flatpak

Host Platform Support (Platform support)
macOS | Windows | Linux
--- | --- | ---
x86‑64 | arm64 | x86 | x86‑64 | arm64 | x86 | x86‑64 | arm | arm64
|  |  |  |  | △ | ● | △ | ●

Flatpak provides a way for developers to distribute apps to Linux users in a format that is independent of the specific distribution used by the end-user. It allow packaging applications for use on any common Linux distribution, including Ubuntu, Debian, Fedora, and more. There are some system packages needed to run and build Flatpaks; see the Flatpak setup guide for more details.

A Flatpak app is built by compiling against a `runtime`. Runtimes provide the basic dependencies that are used by applications. Each application must be built against a runtime, and this runtime must be installed on a host system in order for the application to run (Flatpak can automatically install the runtime required by an application).

The end user will install the Flatpak into their local app repository; this can be done by installing directly from a single file `.flatpak` bundle, or by installing from a package repository like Flathub. Apps can be installed into user-space, or if the user has sufficient privileges, they can be installed into a system-wide app repository.

Briefcase currently supports creating `.flatpak` single file bundles; end users can install the app bundle by running:

    $ flatpak install --user App_Name-1.2.3-x86_64.flatpak

substituting the name of the flatpak file as appropriate. The `--user` option can be omitted if the user wants to install the app system-wide.

The app can then be run with:

    $ flatpak run com.example.appname

specifying the app bundle identifier as appropriate.

Briefcase can be published to Flathub or another Flatpak repository; but Briefcase does not currently support automated publication of apps.

## Icon format

Flatpak uses `.png` format icons. An application must provide icons in the following sizes:

- 16px

- 32px

- 64px

- 128px

- 256px

- 512px

Flatpaks do not support splash screens or installer images.

## Application configuration

The following options can be added to the `tool.briefcase.app.<appname>.linux.flatpak` section of your `pyproject.toml` file:

finish_arg

The arguments used to configure the Flatpak sandbox. `finish_arg` is an attribute that can have additional sub-attributes; each sub-attribute maps to a single property that will be added to the app’s manifest. For example, to add `--allow=bluetooth` as a finish argument, you would specify:

    finish_arg."allow=bluetooth" = True

Briefcase adds the following finish arguments by default:

- `share=ipc`

- `socket=x11`

- `nosocket=wayland`

- `share=network`

- `device=dri`

- `socket=pulseaudio`

- `filesystem=xdg-cache`

- `filesystem=xdg-config`

- `filesystem=xdg-data`

- `filesystem=xdg-documents`

- `socket=session-bus`

These can be disabled by explicitly setting their value to `False`; for example, to disable audio access, you would specify:

    finish_arg."socket=pulseaudio" = false

flatpak_runtime_repo_alias

An alias to use when registering the Flatpak repository that will store the Flatpak runtime used to build the app. By default, Briefcase will use Flathub as its runtime repository, with an alias of `flathub`.

flatpak_runtime_repo_url

The repository URL hosting the runtime and SDK package that the Flatpak will use. By default, Briefcase will use Flathub as its runtime repository.

flatpak_runtime

A string, identifying the runtime to use as a base for the Flatpak app.

The Flatpak runtime and SDK are paired; so, both a `flatpak_runtime` and a corresponding `flatpak_sdk` must be defined.

flatpak_runtime_version

A string, identifying the version of the Flatpak runtime that should be used.

flatpak_sdk

A string, identifying the SDK associated with the platform that will be used to build the Flatpak app.

The Flatpak runtime and SDK are paired; so, both a `flatpak_runtime` and a corresponding `flatpak_sdk` must be defined.

modules_extra_content

Additional build instructions that will be inserted into the Flatpak manifest, after Python has been installed and `pip` is guaranteed to exist, but before any app code or app packages have been installed into the Flatpak.

## Permissions

Permissions are not used for Flatpak packaging.

## Compilation issues with Flatpak

Flatpak works by building a sandbox in which to compile the application bundle. This sandbox uses some low-level kernel and file system operations to provide the sandboxing behavior. As a result, Flatpaks cannot be built inside a Docker container, and they cannot be build on an NFS mounted drive.

If you get errors about `renameat` when building an app, similar to the following:

    [helloworld] Building Flatpak...
    Downloading sources
    Initializing build dir
    Committing stage init to cache
    Error: Writing metadata object: renameat: Operation not permitted
    Building...

    Error while building app helloworld.

    Log saved to ...

you may be building on an NFS drive. Move your project to local storage, and retry the build.