Open Source Summit Europe 2022

A popular way to implement system updates is through the A/B scheme, in which you have two copies of the root filesystem, one which is active, and one that is meant to contain the next update. When a new update is successfully applied, you need to make the corresponding partition become the new active one. That's when a number of practical questions arise, such as how to identify the active partition, how to detect when the new system fails to boot properly, and how to fall back to the previous version? It was hard to find documentation about how U-Boot could address such needs to implement a functional and failsafe A/B system update mechanism. This presentation proposes to address this need by sharing the practical solutions we found, using lesser known commands and capabilities in U-Boot. We will also explain how the Linux side can cooperate with the U-Boot side. Fortunately, you won't need to erase half of your brain to get updated on this topic.