Flatpak原理#

本页面简单介绍了Flatpak内部工作原理。虽然仅仅是使用Flatpak没必要熟悉这些，但是有些人可会会觉得这很有趣。从用户和应用开发者的角度来看，了解Flatpak的体系结构还有助于更好地理解它的工作方式和原因。

应用级Git#

Flatpak is built on top of a technology called OSTree, which is influenced by and very similar to the Git version control system. Like Git, OSTree allows versioned data to be tracked and to be distributed between different repositories. However, where Git is designed to track source files, OSTree is designed to track binary files and other large data.

Internally, Flatpak therefore works in a similar way to Git, and many Flatpak concepts are analogous to Git concepts. Like Git, Flatpak uses repositories to store data, and it tracks the differences between versions.

With Flatpak, each application, runtime and extension is a branch in a repository. An identifier triple, such as com.company.App/x86_64/stable is a reference to that branch. The output of a Flatpak build process is a directory of files which is committed to one of these branches.

使用Flatpak安装应用时，会将其从远程仓库中拉入到本地仓库中的新分支。 然后生成从文件系统指向仓库的链接（这些链接是快速解析和高效利用的磁盘空间`硬链接 <https://en.wikipedia.org/wiki/Hard_link>`）。 换句话说，安装的每个应用程序都存储在本地版本控制仓库中，然后映射到本地文件系统。

因此，版本跟踪是Flatpak架构的核心部分，这使得更新软件非常高效。 版本控制也使回滚成为可能，因此如果需要，可以很容易地回滚到以前的版本。

将应用程序存储在本地OSTree存储库中具有其他优点。 例如，它允许对存储在磁盘上的文件去重，所以属于多个应用程序（或运行时）的同一文件仅存储一次。

基础技术#

Flatpak使用了许多已经存在的技术。如：