9742 can't access internal sdcard--Solved

Let me first thank Nicogalan, Traveller1701, and Vampirefo (not necessarily in that order), without which this would not have been possible and I would be minus one tablet. I started with Nicogalan's post here:
http://www.androidtablets.net/threads/coby-kyros-mid9042-stock-rom.62650/page-5#post-318780
and took notes from several pages linked from there. As I found that a pain, and also thought it might be incomprehensible to some, I decided to write this up. Hopefully it's a little easier to follow now. To a large extent I simply copied and pasted these others' work, just so it will be easier to locate.

Also allow me to caution anyone considering this fix: You are messing with system files and thus could easily permanently brick your machine. Neither I nor the people named above will be responsible for that!

Naturally this will require root and adb access to your tablet. Since you are basically swapping your internal /sdcard with your /extsd, you will need a micro-SD card installed.

You have to edit both platform.xml and vold.fstab.

Edit /system/etc/permissions/platform.xml and change the WRITE_EXTERNAL_STORAGE section so it looks like this. If platform.xml isn't edited you won't be able to write to the MicroSD card using an app.

Code:
<permission name="android.permission.WRITE_EXTERNAL_STORAGE" >
<group gid="sdcard_rw" />
<group gid="media_rw" />
</permission>

Then edit /system/etc/vold.fstab to change the mount points so that /mnt/extsd refers to the internal memory and /mnt/sdcard refers to the MicroSD card.
I found it easiest to adb pull these files to a PC in order to edit them with a real keyboard and text editor rather than attempt it with a virtual keyboard on a tiny screen.

Code:
adb devices
adb pull /system/etc/permissions/platform.xml /root/platform.xml
adb pull /system/etc/vold.fstab /root/vold.fstab

You may pull the files to wherever you like, on my Linux box it's easiest for me to use /root/.

My platform.xml already looked like that, probably because I have the Mobiz_v.2 ROM. My vold.fstab wound up looking like this:
Code:
## Vold 2.0 fstab for HTC Passion
#
## - San Mehat (san@android.com)
##
#######################
## Regular device mount
##
## Format: dev_mount <label> <mount_point> <part> <sysfs_path1...>
## label - Label for the volume
## mount_point - Where the volume will be mounted
## part - Partition # (1 based), or 'auto' for first usable partition.
## <sysfs_path> - List of sysfs paths to source devices
######################

# Mounts the first usable partition of the specified device
#/devices/platform/awsmc.3/mmc_host for sdio
dev_mount sdcard /mnt/sdcard auto /devices/platform/sunxi-mmc.1/mmc_host /devices/platform/sunxi-mmc.0/mmc_host
dev_mount extsd /mnt/extsd auto /devices/virtual/block/nandi
dev_mount usbhost1 /mnt/usbhost1 auto /devices/platform/sw-ehci.1 /devices/platform/sw_hcd_host0 /devices/platform/sw-ehci.2

what I did was swap the parts after /devices/ on the sdcard and extsd lines.
Then back to terminal:

Code:
adb devices
adb remount
adb push /root/vold.fstab /system/etc/vold.fstab
adb reboot
exit

Without the remount command the push will fail as /system is mounted
r/o by default.

I now have a functional tablet once again. I do not think that CWM will give me a complete nandroid backup anymore, I expect it to get confused with the strange mountings. I have also observed a problem updating apps through Play Store, but that may be a coincidence involving my poor internet connection. Amazon Appstore can install stuff. YMMV!

Edit: there is a problem with Play Store. It simply cannot download apps or updates. I have tried reinstalling it, I have tried force-stop-clear-data-reboot, all to no avail. It runs, shows screenshots & writeups and all, asks me to accept permissions, then errors out, something about not able to download data from server. I'm guessing that either its buffer or its temp d/l location went south along with my internal sdcard, but it's just a guess. I can live without it on this tablet, and will unless someone has a magic wand handy.