balenaEngine aufs storage driver deprecation

The balenaEngine is a specialized container engine and a critical element in balenaOS, the lightweight, robust and reliable Linux-based embedded operating system running on over 100 different boards and designed specifically to run containers.

balenaEngine is a fork from Moby Project, which deprecated the use of the aufs storage driver with the 19.03.x release series. The aufs storage engine was also problematic as it did not allow the preloading of applications on non-Linux-based operating systems.

With that in mind, it will come as no surprise that balenaOS would also look to deprecate the use of aufs. However, existing applications in the field on the aufs storage driver would need to be re-downloaded by the engine to run on the new storage driver, and this might incur costs and become an expensive process for fleets on costly bandwidth, such as cellular networks.

To facilitate this update, the balenaEngine now implements a migration step that will convert the existing applications from aufs to overlay2 avoiding application re-downloads.

The migration should be transparent to users in most cases, although the first boot after a hostOS update will take longer to complete as the migration occurs.

In the unlikely case that the migration fails, the system will still fall back to a re-download.

The following devices will be affected by this migration when updating to a BalenaOS version >= 2.85.0, including ESR (Extended Support Release) >= v2022.01

If your fleet is running a private device type, please contact us through our support channels and we can check whether your device type is affected.

Feedback from our support channels has resulted in some bug fixing, for example, extending timeouts for big application migrations, so as always updating to the most recent balenaOS release either in the rolling or ESR (Extended Support Release) versions is recommended.

As always, report any problem with this feature through our support channels or forums.