[LG Optimus 4X HD] Fluoxetine:
Okay i only started looking at multirom around 4hours before releasing this, so i am aware we already have a multiROM thread, however i do believe it's outdated, and perhaps unsupported now, so i am merging a supported multirom with my TWRP thread where i will be keeping both updated, thanks to [MENTION=3418703]Tasssadar[/MENTION] for bringing multiROM to the android community. I failed hard with outdated sources from adam so i have written my own stuff, but i think iodak is using his .diff​

Taken and modified from official thread at Flo

Introduction

MultiROM is one-of-a-kind multi-boot mod for Nexus 7. It can boot any Android ROM as well as other systems like Ubuntu Touch, once they are ported to that device. Besides booting from device's internal memory, MultiROM can boot from USB drive connected to the device via OTG cable. The main part of MultiROM is a boot manager, which appears every time your device starts and lets you choose ROM to boot. You can see how it looks on the left image below and in gallery. 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, which can be used to ship other Linux-based systems.

Features:

* Multiboot any number of Android ROMs

* Restore nandroid backup as secondary ROM

* Boot from USB drive attached via OTG cable

You can also watch a video which shows it in action.​

Warning!

It _is_ dangerous. 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 and you will have to flash factory images again. Make backups. Always.​

Installation

Manual installation

Find all needed files here: MOD Edit: Links removed

I think Iodak has the kexec patch so use his Rom, i'm not too sure on how to add a kexec so i'll look into it, this does support KK roms as i tried it, and so has dan.

MultiROM has 3 parts you need to install:

MultiROM multirom.zip - download the ZIP file from second post and flash it in recovery.

Modified recovery (TWRP_Mrom.zip) - download and flash in recovery.

Patched kernel - Iodaks kernel i believe is kexec patched, worked for me, have a play, i use share kernel for KK roms of the same type. I suggest this.

You current rom will not be erased by the installation.

Download links are somewhere below

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Adding ROMs

Android

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

Updating/changing ROMs

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.

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.

Source code

MultiROM - https://github.com/Tasssadar/multirom/tree/master (branch master)

Modified TWRP - https://github.com/Tasssadar/Team-Win-Recovery-Project (branch master)

Device Tree for building Mrom and TWRPhttps://github.com/Fluoxetine/android_device_lge_p880 (branch TWRP)​

Thanks and Links

Official thread with screenshots, donate link, and changelogs

Original Thread for 4xHD by [MENTION=4719724]Adam77Root[/MENTION]

FAQ and other notes

About security

In order to make multi-booting possible, MultiROM has to sacrifice some security measures. Firstly, on secondary Android ROMs, /system is not mounted read-only. While there are other things preventing malicious software from messing with /system, this might potentialy make it easier for such software to attack that system.

Next, MultiROM doesn't work with /data encryption. Not many people who use custom ROMs also use encryption anyway, so that isn't much of a concern.​

What do the ROMs share?

All ROMs are separate, except /sdcard, which is shared between all Android ROMs.​

How many ROMs can I have?/Where are the ROMs stored?

You can have as many ROMs as you can fit in your /sdcard. All the ROMs are stored in /sdcard/multirom/roms or on an USB drive. This folder is unaccessible in Android, to prevent mediascanner from scanning it. You can either in recovery, or obtain root and go to /data/media/0/multirom/roms.
​

Can I have different versions of Android working alongside

Yes. As long as you select "Don't shere kernel" when installing the secondary ROM, the systems are separated.​

MultiROM recovery says it's 2.6.3.0. Why isn't it updated to 2.6.3.*highernumber*?

It is, it just shows wrong version.​

The menu with all the ROMs won't show up during boot, how to fix it?

Either re-flash the MultiROM zip or go to recovery, Advanced -> MultiROM -> Inject curr. boot sector.

The reason for this is that something rewrote your boot.img, which happens for example when you flash a kernel. MultiROM's boot menu is part of the boot image, so it has to be added into it again.
​

Will you port MultiROM to device X?

No, probably. I won't port MultiROM to any device I don't own, because it is very difficult to provide the level of support I want to provide if I can't test things myself, as proven by the Nexus 4 port. I'll probably keep buying Nexus devices and keep porting MultiROM to those myself, but I can't buy every single device - I'm still a student, all my existing devices were bought using some kind of money grant or donations from users.

But, you can port it yourself, the wiki should give you at least some idea how to do that: https://github.com/Tasssadar/multirom/wiki/Porting-MultiROM
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Message from Fluoxetine

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Changelog from my end and not multiROM ;) (Ascending Order)

- [I] Release within 4 hours of solid working on it [/I]
- Fix Recovery
- Fix touch input
- Build Multirom.zip
- Remove weird vibration
- Fix MultiRom button
- Fix Layout
- Build Modified TWRP
- Create TWRP.fstab
- Build MultiRom.zip
- Fix Sizing
- Build Initial MultiRom.zip
- Create mr_init_devices.c
- Create a modified BoardConfig.mk
- Sync Modified TWRP
- Sync MultiRom
- Sync Omni