Flatpak developer Alexander Larsson has recently released Flatpak 0.9.10, the latest version of this popular framework for sandboxing or distribution of application packages.
Although Flatpak 0.9.10 represents a simple update that fixes a small problem with the D-Bus proxy, the version on which it is based, Flatpak 0.9.9, arrived last weekend with more improvements, including splitting the command flatpak-builder in a separate tool that application developers can use to create Flatpak-like packages from their applications.
Therefore, Flatpak-builder is now a standalone open source tool that can be downloaded from its own Github page, and is designed as a utility focused on the flatpak command for creating Flatpaks from source files.
It is a very interesting decision on the part of the Flatpak team as it will drive the adoption of this format across more GNU / Linux distributions.
How to install Flatpak-builder on Ubuntu or any other Linux distribution
It is very easy to create a Flatpak package from a source file. This method basically refers to the inclusion of a Linux app in a special package that will only be available as a Tarball file in the Flatpak format. All you have to do to download and install Flatpak-builder on Ubunt or your favorite Linux distribution is to enter the following commands, using the traditional autoconf-style mechanism.
./configure [args] make sudo make install
Note that Flatpak-builder is based on Flatpak, so you should make sure to install it before installing Flatpak-builder using the commands above. Once Flatpak-builder is installed, you can use it via the command line to 'package' your applications in the Flatpak format. The detailed instructions found here, where you will also find all the necessary info to start with the creation of Flatpaks from Linux apps in order to easily distribute them on multiple operating systems.