[MOD] [TESTING] Simple A-B MultiBoot


Senior Member
Sep 17, 2015
#include <std_disclaimer.h>

 * Your warranty is now void.
 * We are not responsible for bricked devices, dead SD cards,
 * thermonuclear war or you getting fired because the alarm app failed. Please
 * do some research if you have any concerns about features included in this ROM
 * before flashing it! YOU are choosing to make these modifications and if
 * you point the finger at us for messing up your device, we will laugh at you. Hard & a lot.

What is this?

this is a simple zip for A/B devices only that will separate the ROM in your current slot so that it won't interfere with the ROM in the opposite slot, which we'll call the primary ROM.

How does it work?

it modifies the fstab of the ROM in your current slot to have separate data and shared internal storage, data will be in /data/media/multiboot in the actual data partition.

What's the catch?

this of course comes with a few unsolvable issues such as:

1- SElinux must be permissive on the ROM you're multibooting (secondary ROM)
2- NO ENCRYPTION, do not use this on encrypted data, it will break everything.
3- don't use multiple users on the secondary ROM, it's unlikely to work (not tested)
4- Magisk modules exhibit weird behavior, such as modules from the primary ROM showing in the secondary, it is strongly recommended to use core only mode if you're using Magisk (only on the secondary ROM)
5- and most importantly, screen lock is likely to stop working on the primary ROM every time you switch and switch back, once you're back to the primary ROM, your PIN/pattern might not be recognized, same thing that happens some times when you restore the data partition, it's recommended to remove your screen lock before switching to the secondary ROM, or delete /data/system/locksettings.db once you're back.
6- and lastly, this is unlikely to work on stock/ported ROMs, not tested though, feel free to try.

and that's all OK, as this is intended for testing purposes only, maybe you want to test a new ROM or a GSI but don't want to commit to it yet, this doesn't mean you don't need to backup your data, this has only been confirmed working on ONE device, no guarantees it will work for you.


flash the secondary ROM normally (flash, switch slot, reboot recovery, gapps, magisk etc...)
flash this zip
flash Kernel Sepolicy Patcher and switch to permissive.