[Galaxy S III I9305 (4G LTE + 2GB RAM) Android Deve] 西村大一:
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(Click on the image above to download my MultiROM Manager App)​

MultiROM for the Samsung Galaxy S3 i9305, brought to you by Alexander_the_B0ss​

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#include <std_disclaimer.h>

/*
* Your warranty is now void.
*
* I'm 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 me for messing up your device, I will laugh at you.
*
*/

Introduction

MultiROM is one-of-a-kind multi-boot mod for Galaxy S3 4G. It can boot any Android ROM . Besides booting from device's internal memory, MultiROM could boot from external SD card(untested). The main part of MultiROM is a boot manager, which appears every time your device starts and lets you choose ROM to boot. ROMs are installed and managed via modified TWRP recovery. You can use standard ZIP files to install secondary Android ROMs and MultiROM even has its own installer system.

Features:

* Multiboot any number of Android ROMs (as many as your internal memory can hold)

* Restore nandroid backup as secondary ROM (damn useful feature)

* Boot from Internal memory and MicroSD Card

Warning!

This whole thing is basically one giant hack - none of these systems are made with multibooting in mind. It is no longer messing with data partition or boot sector, but it is possible that something goes wrong (even if never happened until now) and you will have to flash stock firmware with Odin. Make backups. I personally can't stress enough for you people to make nandroids becuase you never know.

Installation

Via MultiROM Manager app

This is the easiest way to install everything MultiROM needs. Install the app Install my modified app and select MultiROM and recovery on the Install/Update card the app is still in alpha, so don't select install, use manual install below. If the Status card says Kernel: doesn't have kexec-hardboot patch! in red letters, you have to install also patched kernel - either select one on the Install/Update card or get some 3rd-party kernel here on XDA. You are choosing kernel for your primary ROM, not any of your (future) secondary ROMs, so select the version accordingly.

Press "Install" on the Install/Update card to start the installation.

Manual installation

Firstly, there are videos on youtube. If you want, just search for "MultiROM installation" on youtube and watch those, big thanks to all who made them. There is also an awesome article on Linux Journal.

Note 1: Your device must not be encrypted (hint: if you don't know what it is, then it is not encrypted).

MultiROM has 3 parts you need to install:

MultiROM itself - download the ZIP file and flash it in recovery.

Modified recovery - download the ZIP file and flash it in recovery or Mobile Odin app to flash the recovery.img contained inside ZIP.

Patched kernel (Only TWO: AGNi PureCM or AGNi PureSTOCK) - Download the ZIP file and flash it in recovery (seems like kexec-hardboot isn't activated by psndna88, so menu won't show up on boot)

*Downloads in Post #2*

If your MAIN ROM is TouchWiz or TouchWiz based, please use AGNi PureSTOCK kexec-hardboot status unknown, someone with stock rom please install app and tell me if kexec-hardboot is enabled.

If your MAIN ROM is not TouchWiz, but CM or AOSP (basically custom rom except MIUI) use AGNi PureCM no kexec-hardboot, tested.

You current rom will not be erased by the installation.

Adding ROMs

Go to recovery, select Advanced -> MultiROM -> Add ROM. Select the ROM's zip file and confirm.

Using MicroSD Card

(UNTESTED)

During installation, recovery lets you select install location. You just select the location (extX, NTFS and FAT32 partitions are supported) and proceed with the installation.

If you wanna use other than default FAT32 partition, just format it in PC. If you don't know how/don't know where to find out how, you probably should not try installing MultiROM.

If you are installing to NTFS or FAT32 partition, recovery asks you to set image size for all the partitions - this cannot be easilly changed afterward, so choose carefully. FAT32 is limited to maximum of 4095MB per image - it is limitation of the filesystem, I can do nothing about that.

Installation to MicroSD Card takes a bit more, because the external memory is (usually) slower and it needs to create the images. Also boot process is longer, highly depends on card's class. You can find ROMs installed on SD card in the "External" tab in boot menu.

Updating/changing ROMs

1. Primary ROM (Internal)

Flash ROM's ZIP file as usual, do factory reset if needed (it won't erase secondary ROMs)

Go to Advanced -> MultiROM in recovery and do Inject curr. boot sector.

2. Secondary Android ROMs

If you want to change the ROM, delete it and add new one. To update ROM, follow these steps:

Go to Advanced -> MultiROM -> List ROMs and select the ROM you want to update.

Select "Flash ZIP" and flash ROM's ZIP file.

Explanation of recovery menus

Main menu

Add ROM - Add ROM to boot manager

List ROMs - List installed ROMs and manage them

Inject curr. boot sector - Use this option if MultiROM does not show up on boot, for example after kernel installation.

Settings - Well, settings

Manage ROM

Rename, delete - I believe these are obvious

Flash ZIP (only Android ROMs) - Flash ZIP to the ROM, for example GApps

Add/replace boot.img - Replaces boot.img used by the ROM, this is more like developer option.

Screenshots

Application

Recovery (Sorry for pictures...)

Bonus pic(zoom to see the RGBG-Matrix (PenTile))

My Homescreen and Lockscreen (for those interested)

Big thanks to Tasssadar for this awesome utility.

XDA:DevDB Information

MultiROM, multiboot tool for Samsung Galaxy S3 4G (i9305), Tool/Utility for the Samsung Galaxy S III I9300

Contributors

Alexander_the_B0ss

Version Information

Status: Beta

Current Beta Version: v32

Beta Release Date: 2015-08-30

Created 2015-08-29

Last Updated 2015-09-02