[LG Optimus 3D] dreccon:
Instructions on setting up the ROMs:

In this guide, I will concentrate on how to setup your EXTERNAL SD, because the latest CM10 and CM10.1 kernels modified by Berni expect to find partitions there!

First of all, you need to have ADB installed on your PC and CWM (or other recovery) on your phone. You also need to have unlocked bootloader if you are running ICS. There are other threads that explain how to do all that.

1. BACKUP your EXTERNAL SD card. IT WILL BE ERASED!

2. Download the primary and secondary ROMs of your choice

3. Do the necessary modifications to the secondary ROM as instructed by Berni (Do NOT use Windows Notepad for this. It corrupts the script. Download and use Notepad++ instead).

4. Download the kernels that match your ROMs (as described in Berni's guide).

5. Copy all to your INTERNAL SD (as I said, the external sd will be erased).

6. Boot into recovery, connect to PC via ADB and prepare partitions as instructed by Berni (this is when your card loses all data).

... Detailed Setup Instructions:

Some people reported trouble when trying to partition external SD cards larger than 8GB. So, I rewrote Berni's guide and added a little trick to help.

Follow this guide to partition your EXTERNAL SD card:

1. Turn off your phone. Keep Vol- 3D and Power keys until the LG logo shows. Release all keys. Wait a few sec.

2. You are now in Recovery. Connect your phone to PC with a USB cable, press Windows Start Menu, type:

and hit enter.

3. In the new window that has opened type:

For a 32 GB card, you'll get something like this:

Model: SD 00000 (sd/mmc)
Disk /dev/block/mmcblk1: 31.4GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number Start End Size Type File system Flags
1 [b]1049kB 31.4GB[/b] 31.4GB primary fat32 lba

Write down the Start and End numbers

For cards larger than 8GB, the End Number is shown in GB. Multiply it by 1000 to cnvert it to MB (31400MB in our example). Make sure you use values in MB and NOT in GB in the commands below.

4. Type

At this point, because not all cards have exactly the same capacity, you need to know exactly how much space you have left. Type:

You get somehing like:

Model: SD 00000 (sd/mmc)
Disk /dev/block/mmcblk1: 31.4GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number Start End Size Type File system Flags
32.3kB 1049kB 1016kB Free Space
1 1049kB 29.4GB 29.4GB primary fat32 lba
2 29.4GB 30.1GB 700MB primary ext2
3 30.1GB 31.3GB 1200MB primary ext2
31.3GB 31.4GB [b]87.7MB[/b] Free Space

Note the size of your last free space (87.7MB here). Anything larger than 67.1MB will be sufficient.

Type:

this time you get:

Model: SD 00000 (sd/mmc)
Disk /dev/block/mmcblk1: 31.4GB
Sector size (logical/physical): 512B/512B
Partition Table: msdos

Number Start End Size Type File system Flags
1 1049kB 29.4GB 29.4GB primary fat32 lba
2 29.4GB 30.1GB 700MB primary ext2
3 30.1GB 31.3GB 1200MB primary ext2
4 31.3GB 31.4GB 90MB primary ext2

5. Turn off your phone and boot again into recovery.

Type:

Your new partitions are now ready!

7. Flash the ROMs (you may want to keep your original ROM and flash only the secondary one)

8. Flash your primary kernel and reboot to system.

Rebooting will now load your primary ROM.

Partitioning the easy way!

Instead of step 6, you may put your microSD card to your PC using a Card-Reader. Then you may use MiniTool, EaseUS or other freeware partitioning tool to create your partitions. Shrink your main partition and make three new PRIMARY EXT3 partitions AFTER your main one. The 1st (system2) must be 700MB. The second (data2) at least 1GB (you can make it larger if you like to install lots of apps)! The 3rd one (cache2) should be around 100MB. So, do the math and make sure you have shrunk your fat32 partition according to your needs first. After you're done, eject your card from the PC, put it in your phone and continue to step 7.

Important:

If for your own reasons you need to create more than the 4 primary partitions mentioned above, then you must convert your card to GPT (GNU Partitioning Table). Minitool has that option. This is because the default MBR (Master Boot Record) partitioning does not support more than 4 primary partitions on the same medium. This is also how the internal memory of our phones is divided into a large number of partitions (P920: 15, SU760: 17) and they are all primary.

New: Easiest partitioning ever!

A new app, AParted, has appeared on PlayStore. You can use it to create both MBR type (up to 4 primary) and GPT type (up to 128 primary) partitions.

Instructions on ROM switching:

1. Go to Play Store and install SManager

2. Download the attachment from 1st post, unzip it and place the DualBoot folder on your phone (anywhere you like)

3. Unzip your primary kernel, place boot.img into your DualBoot/img folder and rename it to boot1.img

4. Do the same for your secondary kernel, but rename it to boot2.img

5. Run SManager, browse to your DualBoot folder and select "Switch_ROM".

6. Mark favourite and su options and run the script.

Your phone will now reboot to your secondary ROM. Use the same script to go back to your primary ROM.

7 (optional). SManager has a homescreen widget system. It lets you add buttons in your homescreens that will directly run the linked script (it has to be put in favourites first).

Alternatively, you may download Flashify from Play Store and flash your desired Kernel.img from there. The advantage is that you may keep and test different kernels for the same ROM without having to rename them or put them in the IMG folder (less initial setup). The disadvantage is that it requires more clicks to switch every time.

Instructions on Backup/Recovery/Wipe:

These scripts work for EXTERNAL SD ROM installations!

1. For full functionality, you must be on

PRIMARY ROM

(you can't expect to wipe or restore a running system)!

2. Make sure you have at least 2GB free space on your external SD if you want to make a backup.

3. Inside your DualBoot folder there is a script: "Recovery_Tools". Run the script with SManager (make sure you have the SU and Wlck buttons pressed). For Wlck to work, you must first enable it from SManager settings.

4. You will now enter the Dual Boot Recovery Tools. There are several options. Type the number you want and press enter. All functions are pretty self-explanatory.

It's very important to know that every backup overwrites the previous! The backup is kept in /sdcard/_ExternalSD/ROMs/rom2_backup. If you want to keep more than one backups, you can always rename the folder, but remember to change the name back if you want to restore your ROM.

The "Advanced" option takes you to the "Wipes" menu. For a Factory Reset, you must wipe Data2 and Cache2. For a Full Format, in order to clean-install a new ROM, you may also wipe System2.

Remove Dual Boot - Regain card space:

This is pretty simple:

1. Backup the contents of your SD card.

2. Boot to your primary ROM

3. Go to System Settings/Storage and select Erase SD card.

Case scenario / Easy migration to dual boot:

Say you have already installed CM10 in a single boot setup but you miss the 3D features and you want to restore your good old gingerbread backup or flash the new P920 ICS, but keep your CM10 setup as a secondary ROM in dual boot.

1. Make sure you have at least 4GB free in your external SD.

2. While still in CM10, use SManager to browse to your DualBoot folder, run the "Recovery_Tools" script and select option to "Backup/Migrate ROM1".

(Go fry some bananas cause this will take around 6-7min!)

3. Now backup your external SD to your PC and reboot to recovery.

4. Follow the guide to partition your external SD.

5. Restore your Gingerbread or P920-ICS backup or flash your favorite ROM and reboot into it.

6. Restore your external SD backup from PC.

7. Run the "Recovery_Tools" again and use the "Restore ROM2" option.

(Eat your fried bananas cause this will take another 6-7 min!)

Your original CM10 installation is now relocated to external SD as your secondary ROM. Use my instructions on ROM switching to boot into it.