Elonex One T & One T+, CnM Minibook > Beginners Board

How to restore deleted files on CNM minibook

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Huskypete:
Hi all,
 
I recently deleted everything on my minibook by accident and I was wondering whether anyone knew of any way to recover deleted files. I know that CNM minibooks use a really obscure operating system so I have been unable to find any software that will do the job.

Please help

Cheers

Mijzelf:
The OS is absolutely not obscure, it's just Linux. And I *think* your data is still there, but I'm not sure.
The filesystem is jaffs2, which is a filesystem especially designed for raw flash memory. Flash memory needs a special treatment for accessing. It can be written bitwise, but only in one direction. A '1' can be made '0', but not the other way around. Erasing can only be done in large blocks (usually 64kB). So when a new file is written, it needs a block completely filled with '1'. If that is not available, a large block needs to be erased.
The question now is: Does the filesystem erase the 64kB block directly when the contents becomes obsolete, or does it wait until the space is needed again.
In the first case most of your data will be gone. In the second case it's still there, until it's overwritten.

In the forum you can find directions how to boot your system from a SD card. When you do that, you can copy the (raw) content of the flashmemory to the SD card, or to an USB stick, and depending on the nature of the data try to recover it with various tools from another system.

Huskypete:
Thanks, I'll try that later on.

You may have seriously saved my ass on this one,

Cheers :)

Huskypete:
I think that I've now got the raw data on my SD card. What file extensions should I be looking for? Also, do you have any advice for the best software to use to recover my files from it?

Thanks again,

Pete

Mijzelf:
You used the dd command to copy the data, I hope?

I don't know if it makes sense to search for extensions, because I don't know how jffs2 marks a file as deleted. I'd try the 'deep scan' option of Recuva first. If the files you are searching for are plain text, then this won't work, I'm afraid, because Recuva searches for known headers, which cannot be found in plain text files.
There are some ways to recover plain text files (well, not really, only their contents), but they are all labor intensive, because the data has to be picked manually from the garbage.
Assuming you copied the flash to a file, you could do a 'dd if=file.raw | strings >file.txt' to filter all textdata from the raw data. This will give a huge textfile full of garbage, in which you can search for keywords. The text around the keywords might be the text you are searching for.

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