FASTBOOTAdvancedCaution

fastboot flash --slot=all boot boot.img

Flash partition to both A and B slots simultaneously

Caution RequiredOverwrites backup slot; both slots will share the newly flashed image.

What It Does

Flashes the specified image to both slot _a and slot _b in one command, ensuring slot parity.

Command Syntax

Terminal

$fastboot flash --slot=all <partition> <image.img>

Parameters & Placeholders Breakdown

This command syntax includes specific placeholder tokens. Below is an explanation of what each word represents and concrete real-world values to replace it with:

<partition>Hardware Block Partition Name

The specific storage partition table name on the device (e.g., boot, init_boot, recovery, vbmeta, system, product).

Real-world value:boot or recovery or vbmeta

Command syntax: fastboot flash boot magisk_patched.img

On A/B slot devices, Fastboot automatically appends your current slot (e.g. boot_a).

Usage Examples

$fastboot flash --slot=all boot boot.img

$fastboot flash --slot=all vbmeta vbmeta.img

Options & Flags

Flag / Parameter	Description
--slot=all	Target both slot _a and slot _b.

OFFICIAL COMPANION GUIDE

Flashing Generic System Images (GSI) / Project Treble?

Learn how to enter fastbootd, erase and resize logical dynamic partitions, and disable dm-verity with the complete handbook by @mkr-infinity:

Open GSI Flashing Guide

Prerequisites & Requirements

Unlocked bootloader
A/B partitioned device

Related Commands

fastboot set_active <a|b|other>

Switch active boot slot on A/B device

fastboot flash boot <boot.img>

Flash kernel / ramdisk to boot partition

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Direct technical assistance & ROM flashing troubleshooting by Mohammad Kaif Raja.

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