I'm writing in the hope that this can help others. However, most of what follows has already been written.
1. The SD card.
In Ubuntu one can easily prepare the SD card using gparted, installed via
sudo apt-get install gparted
on the command line. A helpful web page for how to use it is
<http://forum.xda-developers.com/showthread.php?t=535914> .
As has been said, unpacking the rootfs file is also easily done on the command line via
tar -pxjvf 060713.tar.bz2
in the ext3 partition containing 060713.tar.bz2 that can be find under the /media directory.
2. The M92.
Create a directory named
update
in the internal storage of the M92 containing two files:
flash.oar
and
uImage-initramfs
The second file is to be downloaded as explained by Seaniko in the initial post; the first file should consist of the following three lines:
#!/bin/sh
dd if=/media/flash/update/uImage-initramfs of=/dev/mmcblk0 bs=512 seek=12288
reboot
as has been mentioned before. This file can be produced by modifying a previous flash.oar file posted by Seaniko here:
https://www.mobileread.com/forums/sho...&postcount=169
3. The procedure.
Click the flash.oar file in the M92. After a few moments the device will reboot. Shutdown the M92. Insert the SD card. Down-pressing the joystick turn the device on. The phrase ``Software update request detected, checking updates'' will appear. Release the joystick and wait. The miracle of Obuntu should happen. Thank you very much Seaniko! (P.S. You can subsequently delete the update directory from the M92 internal storage.)