[Verizon Samsung Galaxy S III] cyanodro1d:
Loong time lurker, first time poster. I couldn't post a reply in the development forum, obviously. Maybe someone can link to this in relevant threads over in development.

This is a guide for those who are/were using the extsd2internal to swap storage which no longer works after the 4.1.2 OTA or want to do take advantage of this mod: http://xdaforums.com/showthread.php?t=1849860 OR it MIGHT work for other ROMs which want to use this method for the Galaxy S3.

After the OTA, and getting back up and running, I could not get the script to work correctly with this error: "no such file or directory" and doing some sleuthing, it seems Verizon (in their infinite wisdom) changed the mounts, or maybe it did this because gremlins/gnomes, maybe because Vzw/Samsung knows about the swapping method, who knows. Anyways, here is the fix that worked for me:

PreReqs:

Stock ROM 4.1.2 OTA

Rooted (duh)

BusyBox

SManager ads

Terminal Emulator

Root Explorer in R/W mode

extsd2internalsd mod installed/script in the correct place!

BACKUPS!! Make a nandroid backup before you do ANY tinkering people, and copy it to a safe place like your computer.

Let me be clear, for the love of bits and bytes, do not just keep one copy on the sdcard in the phone!!

1) To find the /dev/block/vold for the external sd card, open Terminal Emulator and run this command. Grant it root access when prompted:

su ls /dev/block/vold

Write down or make a note of the numbers. (For me there were only 2, 179:32 and 179:33) Now run these commands:

adb shell
cat /proc/mounts

There will be a whole lot of text that shows up, you are looking for "/dev/block/vold/179:xx" and in the same line there is "/storage/extSDCard"

Alternate method, after you are in shell run command and look for mmcblk1p1:

cat /proc/partitions

The number in the "minor" column, that's the new number!

Double-check that the blocks are right for the sd card's partition size.

Note: I tried using mmcblk1 and it didn't work, then tried mmcblk1p1 and VIOLA! Yay, trial and error.

2) In SManager, edit the extsd2internal script, and replace the 179:97 to 179:*new number* (again, for me it was 179:33)

3) Reboot or just "run" the script in SManger and wait a few moments, then check Settings>Storage.

Here is what my script looks like:

#!/system/bin/sh
#extsd2internalsd is a modification that allows to switch internal sd to external sd and viceversa. With this you can use default internal sd only for app storage #and the external sd to store all apps resource and all others stuff. The resut is a very big increase of installable apps on gs3
#All credits to Mattiadj of xda forum for the idea and script and to mike1986 for the cmw zip.
#xda thread url at http://xdaforums.com/showthread.php?t=1772234
#Script Modified for U.S. Galaxy S3s by Zedomax at GalaxyS3Root.com to be compatible when sdcard is not inserted.

busybox mount -o remount,rw /
busybox mount -t vfat -o umask=0000 /dev/block/vold/179:33 /mnt/sdcard
busybox mount -t exfat -o umask=0000 /dev/block/vold/179:33 /mnt/sdcard
if busybox mount | busybox grep vold/179:33; then
busybox mount -o bind /data/media /mnt/extSdCard
fi

If this didn't work for you, I am a complete n00b, so I will do my best, but don't expect much.

Things to double check:

Permissions on the extsd2interal script in Root Explorer should have all the boxes checked EXCEPT the last 3 at the bottom.

SManager script should be set to "Su" and "Boot"

OTA Headaches? Use this guide to keep root and boot unlocked worked PERFECTLY: http://xdaforums.com/showthread.php?t=2186574#8 I did a nandroid restore to pre-OTA since it borked the first go-around, and then used this method.

Take home message: MAKE BACKUPS!

Credits / Current Build of this mod:

http://xdaforums.com/showthread.php?t=1772234

This mod does work, and just replacing the old with the new (still have to add it in SManager) will get the job done. The new script is significantly different, and I am sure there are reasons, but without a changelog...

Forum Community: Created the thread here because I couldn't find another thread specific to this environment with all the relevant information in one place. If anyone has seen any errors of my ways, please, please reply with what's up.