Flatpak

Host Platform Support (Key)
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

Splash Image format

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:

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.

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.