Ab Multiboot -

Ready to implement this on a Linux machine or SBC? Here is a practical guide using RAUC and GRUB.

To truly master ab multiboot, you must understand the boot flow. Here is the step-by-step mechanics:

| Aspect | A/B for updates | A/B for multiboot | |--------|----------------|-------------------| | Safety | Update rollback safe | Switching slots retains both ROMs | | Storage | Requires ~2x space for system/vendor | Same limitation | | Multiboot ease | Not designed for it, but possible | Requires custom recovery or DSU | | Official support | Yes (since Android 7) | Only DSU (temporary GSI) | ab multiboot

Install GRUB and enable the boot_once feature. Edit /etc/grub.d/40_custom:

menuentry "Boot Slot A" 
   set root=(hd0,1)
   linux /vmlinuz root=/dev/mmcblk0p2 slot=A
menuentry "Boot Slot B (Once)" 
   set root=(hd0,3)
   linux /vmlinuz root=/dev/mmcblk0p4 slot=B
   set boot_once=1

You are likely already using ab multiboot without realizing it. Ready to implement this on a Linux machine or SBC

Traditional multiboot setups (often dual-booting Windows and Linux) rely on a single system partition and a shared bootloader. If the single partition becomes corrupted or an update fails halfway through, the device cannot boot.

A/B Multiboot solves this by dividing the storage into two distinct sets of bootable partitions: You are likely already using ab multiboot without

Keep your daily driver on Slot A while testing a beta OS on Slot B. If the beta crashes, just reboot — Slot A is untouched.