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Why Google added it
Before AVB (Android 7 and earlier), a thief or malware with brief device access could flash a modified boot.img or inject code into system partition. Android would boot it without objection. AVB closes that gap: the bootloader is the root of trust, and it verifies every image before loading it.
The chain of trust
- Hardware root — SoC's immutable ROM key.
- Bootloader (LK) — signed by OEM, verified by hardware ROM.
- vbmeta partition — contains hashes of boot, recovery, dtbo, vendor_boot, system.
- boot.img — kernel + ramdisk, hash matches vbmeta's record.
- system/vendor/product — dm-verity verifies each read at runtime using Merkle tree in vbmeta.
Break any link and the next link refuses to run (or displays a warning).
Boot states and colors
AVB defines four states, each shown as a splash screen on boot:
Most ART users will see the orange warning after unlocking the bootloader. It's harmless — the device still boots and runs normally after a 5-second splash. GREEN is only possible on an untouched stock device.
The vbmeta partition
vbmeta is a tiny partition (~4 KB) that holds hashes of every other critical partition. During boot:
- Bootloader loads
vbmeta. - Verifies
vbmetasignature against OEM public key stored in the bootloader. - Reads hashes inside
vbmetaand verifies each partition before loading.
Replacing vbmeta with a disabled (zero-hash) copy is how custom ROM users bypass verification — the bootloader still checks vbmeta's own signature, but every embedded hash now says "trust everything".
dm-verity: runtime integrity
AVB verifies at boot time. dm-verity extends verification to run time. Every disk read from system, vendor, and product is checked against a Merkle tree hash before being returned to userspace. If someone modifies the partition after boot (e.g. physical attack), reads will fail.
What breaks when you modify Android
Common ART/Magisk operations and their AVB impact:
- Unlock bootloader → ORANGE warning on boot, GREEN never again
- Install Magisk / KernelSU → modifies
boot, requires AVB disable or Magisk's own signature - Flash custom ROM → vbmeta must be replaced with the ROM's own vbmeta or disabled
- Modify system partition → dm-verity will crash on first read; must patch vbmeta first
- Factory reset → doesn't change AVB state. ORANGE stays ORANGE.
Can I go back to GREEN?
Only by flashing a stock factory image and relocking the bootloader. Even then, some OEMs (Samsung with Knox, Motorola with Secure Boot) flip a one-way fuse during first unlock that permanently records tampering.
Download Android Root Tool v8.0.1.5
Unlock, relock, vbmeta operations across Infinix, Xiaomi, Motorola and more.