Ab Multiboot Instant
If you’ve ever dual-booted Linux alongside Windows, you know the hassle: GRUB updates overwrite the Windows bootloader, one OS update breaks the other, or you end up reinstalling everything. Enter AB Multiboot — a robust, partition‑aware boot management strategy originally popularized by Chromium OS (and used in some embedded systems) that can save you from bootloader nightmares.
At its core, AB Multiboot is a partitioning and boot strategy that maintains two complete copies of a system’s firmware, kernel, and data partitions—labeled "Slot A" and "Slot B."
Unlike traditional dual-booting, where you choose an OS before the kernel loads, AB Multiboot allows you to switch between two system images while the device is running. The system reboots directly into the alternate slot without a bootloader menu delay. ab multiboot
To switch from Slot A to Slot B at runtime:
rauc status mark-active other
sudo reboot
Upon reboot, the system loads Slot B. If the watchdog isn’t fed within 30 seconds, it reboots back to Slot A automatically. If you’ve ever dual-booted Linux alongside Windows, you
Every modern Android device with "Seamless Updates" uses AB. When you download an OTA update, the phone feels snappy because it installs in the background. The "reboot" is just a slot switch.
Why should you abandon your old grub-mkconfig workflow? Let’s compare. Upon reboot, the system loads Slot B
| Feature | Traditional Dual-Boot (GRUB/Windows) | AB Multiboot | | :--- | :--- | :--- | | Switching Speed | 30-60 seconds (full kernel reload) | 5-10 seconds (direct slot flip) | | Safety | High risk of bricking on update failure | Zero risk (automatic rollback) | | Storage Overhead | Low (shares user data) | High (full duplicate system partitions) | | Boot Menu | Manual selection required | Silent; uses metadata flags | | Use Case | Permanent different OSes (Windows + Linux) | Rapid testing, dev builds, embedded systems |
Verdict: Traditional multiboot is for different OSes. AB Multiboot is for different versions of the same OS or instant A/B testing.
Because the bootloader is simple and separate (often a small partition with a fixed path like try A, then B), one OS corrupting its own files won’t take down the bootloader itself.
Ready to implement this on a Linux machine or SBC? Here is a practical guide using RAUC and GRUB.