Collabora, the open source consulting firm that often works with Valve, has a new blog post out from developer Simon McVittie talking a little about their work on SteamOS and the Steam Deck.
SteamOS 2 was originally based on Debian Linux, but this was changed with the new SteamOS 3 to be based on Arch Linux. So yes, for those who still don't know — the Steam Deck runs Linux! It's a Linux handheld gaming PC! I covered it in an initial review, so be sure to take a look.
What's interesting is the explanation of how the update system works that Collabora helped to create:
A handheld device needs a solid update framework, so one of Collabora's major contributions to SteamOS 3 was to help implement seamless system updates. With its new “A/B” design, there are now two operating system partitions, with two different versions of SteamOS. When upgrading, a new operating system image is written to whichever partition is not currently in use, before rebooting the system. A specialized bootloader module then automatically selects the newer operating system and boots into it. If the upgrade was successful, you continue to use the new OS, and the previous system partition is reused for the next upgrade. If the upgraded version does not boot successfully, then the bootloader automatically falls back to the previous system partition, and you can try again later. Of course, new operating system images are downloaded with block-based deltas, so only the changed parts need to be re-downloaded.
Collabora are also part of the team that created Pressure Vessel, the container system that Proton and the Steam Deck use to run games inside for a consistent environment. They say to think of it "a bit like a simplified version of Flatpak for Steam games".