Shipping a production embedded Linux product on an NXP i.MX board eventually leads to the same question: how do we update these devices in the field without bricking them? If the product is going to live for five, ten, or fifteen years, the answer needs to be more robust than “SSH in and run apt upgrade.” For devices that cannot afford to brick under any circumstances, the established answer is A/B system updates: two copies of the system on separate partitions, a bootloader that picks between them, atomic switchover, and automatic rollback if the new copy does not come up cleanly.
This article is a practical, technically detailed walk-through of how to build A/B system updates for NXP i.MX boards. The approach is generic across the i.MX 8, 8M, and 9 families; we have validated it end-to-end on the NXP FRDM-IMX91. Along the way, we cover partition layout, U-Boot configuration, A/B version selection from the bootloader, signed FIT images for verified boot, and dm-verity for runtime rootfs integrity, all the way up to how these pieces plug into a meta-imx build. By the end, you'll have a reference design that updates atomically, rolls back on failure, and cryptographically verifies boot artifacts and rootfs blocks, ready to drive with Rugix Ctrl or any other update engine.
