PRS-T1 "update.img" to boot completely from the SD card?

[jonatasmello]

Hello all!
This is for experienced users (not me) or someone who wants a deep dive into the bits!

I've read almost all the posts for PRS-T1, but couldn't find this:

Is it possible to create an "update.img" to boot completely from the SD card?
Supposing the internal storage is messed up?
(from the SD-rescue package, it is in "OS Firmware/files/update.img")

Something similar to the Raspbery Pi where the boot is all in the SD card (no internal storage)?

Here is my story:

what I did (using the recovery console):
- created a full image backup (almost 2GB) in windows as decribed in another post);
- created one backup for each partition (dd if=/dev/mmcblk2p1 of=/tmp/mmcblk2p1 from 1 to 10);
- removed and recreated the partitions;
- formtated each partition;
- when I was ready to dd the images back, something went wrong and it rebooted! :-O
- then I could not access the console neither the partitions using windows/linux;

- a reboot with the HOME+MENU will keep the power light flashing, and the message "Opening Book" on screen.
- removing and adding the SD card, the SD card led flashes from some time then stops (I thing it is searching for something, but what?)
- I have no access to the console /dev/ttyACM0 in linux or 'Serial Gadget' in windows

Some thoughts:
- As I formated the first partitions mmcblk2p1 and mmcblk2p2, the boot process is not working correctly.
- SD rescue is not working, because boot process is not completed ?
- let's assume that the partitions are OK, but the content is empty.
- the first 20MB in the internal storage are untouched (serial number, MAC addres).


Some experiments:
- I tried to change the /etc/rc.d/rdS in the "update.img" to flash the mmcblk2p1.img back but it didn't worked.
- I mounted the mmcblk2p1.img and copied the "linuxrc" to the "update.img"
- in the "linuxrc" I found out where the "update.img" is mounted:

MOUNT_FILE="/mnt/sd/OS Firmware/files/update.img"
if [ -f "${MOUNT_FILE}" ];
then
/bin/mount -t ext4 "${MOUNT_FILE}" /sysroot -o ro,loop

Some questions:
- How does the boot works?
- Copying the "linuxrc" to the "update.img" actually make it run on boot?
- if yes, can I mount the root in /mnt/sd/img/mmcblk2p1.img instead of the original location?
- is there any full boot img that I can use and connect to the console (U-boot maybe)?


Any ideias are welcome! I will dig into it until I make it works again!

Thanks!
Live Long and Prosper!