[Miscellaneous Android Development] OfficerJimLahey:
An update on this (for all to see) ... :D

So some early testing determined that the file in question to modify for this is \fstab.qcom (off the rootfs).

This is what the file looks like:

# Android fstab file.
# The filesystem that contains the filesystem checker binary (typically /system) cannot
# specify MF_CHECK, and must come before any filesystems that do specify MF_CHECK

#TODO: Add 'check' as fs_mgr_flags with data partition.
# Currently we dont have e2fsck compiled. So fs check would failed.

#<src> <mnt_point> <type> <mnt_flags and options> <fs_mgr_flags>
#/dev/block/platform/msm_sdcc.1/by-name/system /system ext4 rw,barrier=1 wait
/dev/block/platform/msm_sdcc.1/by-name/userdata /data ext4 nosuid,nodev,barrier=1,noauto_da_alloc,errors=continue wait,check,encryptable=/dev/block/platform/msm_sdcc.1/by-name/encrypt
/dev/block/platform/msm_sdcc.1/by-name/sns /sns ext4 nosuid,nodev,barrier=1,noauto_da_alloc,errors=continue wait,check
/dev/block/platform/msm_sdcc.1/by-name/mpt /mpt ext4 nosuid,nodev,barrier=1,noauto_da_alloc,errors=continue wait,check
/dev/block/platform/msm_sdcc.1/by-name/drm /persist-lg ext4 nosuid,nodev,barrier=1,noauto_da_alloc,errors=continue wait,check

This is what it should look like:

# Android fstab file.
# The filesystem that contains the filesystem checker binary (typically /system) cannot
# specify MF_CHECK, and must come before any filesystems that do specify MF_CHECK

#TODO: Add 'check' as fs_mgr_flags with data partition.
# Currently we dont have e2fsck compiled. So fs check would failed.

#<src> <mnt_point> <type> <mnt_flags and options> <fs_mgr_flags>
#/dev/block/platform/msm_sdcc.1/by-name/system /system ext4 rw,barrier=1 wait
/dev/block/mmcblk1p2	/data ext4 nosuid,nodev,barrier=1,noauto_da_alloc,errors=continue wait,check,encryptable=/dev/block/platform/msm_sdcc.1/by-name/encrypt
/dev/block/platform/msm_sdcc.1/by-name/sns /sns ext4 nosuid,nodev,barrier=1,noauto_da_alloc,errors=continue wait,check
/dev/block/platform/msm_sdcc.1/by-name/mpt /mpt ext4 nosuid,nodev,barrier=1,noauto_da_alloc,errors=continue wait,check
/dev/block/platform/msm_sdcc.1/by-name/drm /persist-lg ext4 nosuid,nodev,barrier=1,noauto_da_alloc,errors=continue wait,check

ajoh99 was the tester for this, made the change, rebooted, and nothing happened! Opened the file again, the file reverted.

I did an experiment then...I modified the file, made a small change, saved, closed the editor, reopened it, and the change was still there. Rebooted, and the change disappeared.

Then I found this thread...

http://xdaforums.com/showthread.php?t=443994

...which means boot.img populates the rootfs every time the system is started (loaded into memory, which is why it's called a RAMdisk).

So I went after the source. Extracted [MENTION=5545101]xdajog[/MENTION]'s kernel, unpacked it, changed the needed file, repacked it (after compiling a needed program), and push it to the device. All went well so far. But then, all went downhill after I flashed it. This is what i got in the reboot (picture attached as well, if you can see through the smudges):

Secure booting error!
Cause : boot certification verify

D'oh! Because recovery is accessed via the kernel, and now I have a rejected kernel, all I could do is enter Download Mode and flash back to true stock with the LG Support Tool (and then root, install TWRP, restore from backup).

So that's where I am with that. Unless there is a way to disable the security check, or to certify the ramdisk, I am stuck for now.