[Sprint Samsung Galaxy S III] TodWulff:
Android File System Heirarchy & Symlink Primer anywhere?

Good day. Pseudo-noob here (tech geek, but in x86 and microcontroller context - majority ignorant with *nix/droid - hack winAPI scripter, not a dev by any stretch...).

I have 275+ user apps on my Sprint GS3 (SPH-L710). I am rooted and running SlimRom's 4.2.2 (aokp-based) for the device (wicked nice, btw). Things are reasonably good and stable (gotta love Nova Launcher Prime as a UI too).

I have a Class 10 32G external SD card. I have it formatted with a 20G FAT (16/32? I forget) partition and a pair of 4G ext4 partitions (had been using link2sd successfully since app2sd doesn't work with the 'emulated' internal storage on the GS3...). I created 2ea ext4 partitions as a bit of an experiment, when struggling with the notorious issue that wreaks havoc with said cards in the GS3. Anyways, I have the card protected in the system settings developer options UI and it has been running smooth w/o the effin cyclical remounting issues that have plagued so many. So, I am hesitant to go fracking around just to try to get that orphaned partition back...

Anyways, I am wondering how to do a symlink on the storage/emulated/0/Android/obb folder. I'd like to off-load some of the larger obb files to the ext4 partition. I've been trying to use Speed Software's Root Explorer (v 3.0.1) and it works for letting me create a simlink for an existing folder on the internal storage and link to it from the extsd2 partition, but not the other way around.

Issue 1: I copied the android/obb folder's contents to a new obb folder on the root of the ext4 partition. I them tried to delete the original storage/emulated/0/Android/obb folder and the OS forcibly prevents same (the subfolders for the games'/apps' obb files did indeed delete, however). I see the toast where SU grants Root Browser superuser rights, but the delete event fails with a dialog indicating so.

Issue 2: I then created a test folder on the ext4 partition, put a dummy text file therein, and then tried to symlink the test folder into a folder on the device's internal storage. I am met with an error dialog indicating "link failed Function not implemented". So, I am guessing that either I am trying to symlink to a virtual folder in the android heiarchy (which is confusing as hell, btw - seems a mix of virtual directories w/in physical, and deeper virtual folders pointing to other physical elsewhere in the OS (legacy for compatibility.?.)), or the OS thinks that the ext4 partition is a FAT partition.

I figure that I am on thin ice and that I had better ask for a pointer to a primer on the android OS file directory heiarchy, soes I can get somewhat smarter, before I go totally borking the device (low risk even if I do, as I do have CWM 6.0.3.1, a good recent nandroid backup, and a paranoid number of Titanium BUs :) - all mirrored on my x86 pc).

I have busybox and terminal emulator as well. Are there some command line scripts that I can run that will help me to ascertain if the OS thinks that the sdext2 partition is something other than an ext4 partition?

Also, any guidance you folks can point me to, to help shallow out the learning curve with the Android's FS implementation would be much appreciated. Thank you, in advance. Peace. Out.

-t