Flatpak uses OSTree, like Fedora Atomic Desktops (Silverblue, Kinoite etc) and similar to BTRFS snapshots.
So many files are deduplicated and linked, not actually there
https://gitlab.com/TheEvilSkeleton/flatpak-dedup-checker
50GB without
31GB with deduplication
21,4GB with BTRFS compression
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Linux is a family of open source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991 by Linus Torvalds. Linux is typically packaged in a Linux distribution (or distro for short).
Distributions include the Linux kernel and supporting system software and libraries, many of which are provided by the GNU Project. Many Linux distributions use the word "Linux" in their name, but the Free Software Foundation uses the name GNU/Linux to emphasize the importance of GNU software, causing some controversy.
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What does "ostree hardlinks data blobs internally" mean?
Flatpak uses OSTree - a git-like system for storing and transferring binary data (commonly referred to as 'blobs'), and that system works by addressing such blobs by hashes of their content, using Linux hardlinks (multiple inodes all referring to the same disk blocks) to refer to the same data everywhere it's used.
So basically, whenever Flatpak tells OSTree to download something, it will only ever store only copy of that same object (.so-file, binary, font, etc), regardless of how many times it's used by applications across the install.
Note that this only happens internally in the OSTree repo - i.e.
/var/lib/flatpakor~/.local/share/flatpak, so if you have multiple separate Flatpak installations on your system then they can't automagically de-duplicate data between each other.Thank you for the explanation.