What happens when NOOBs starts installing Arch?

[rPioneer]

This is a question to do with my current thread here http://www.raspberrypi.org/forums/viewt ... 66&t=95328 that I suggest you read (at least some, it is 55 posts long! ) but I thought this was a separate enough question to start a new thread.

I have an SD card with NOOBs on it. I had installed Raspbian and used it for about a year. Apparently the Raspbian root partition is partition 6. By accident, Arch began installing from the NOOBs menu on top of Raspbian. I stopped the install, less than 3 seconds after it started, and switched off the Pi by unplugging it. Raspbian does not boot anymore, and the OK led flashes 4 times because start.elf is missing.

What I would like to know is what does Arch do when it begins installing? What might it have done in those first few seconds? I am trying to retrieve my files, but partition 6 is apparently non-existent- it does not show up as /dev/sde6, or appear using fdisk on an image of the SD card. So, as I said, I would like to know from someone who definitely knows, what does Arch do in that timeframe? Thanks.

[sdjf]

I cannot answer your question about the order of installation activity, but i can make a suggestion about that article you have lost.

when I had an SD card whose file system got totally trashed, I created an .img file of the whole card. I then grepped through that img file for critical keywords, and saved the output to a file, and was able to retrieve some text files that way. If you article was getting composed in a simple text editor, you may be able to do the same thing.

the actual image had various prior versions of what I was looking for, not visible to me when I was working with the SD card itself, but still there as they had not been overwritten with other data bits.

you know how to create an img file, and how to use grep??

I had hunted around for utilities that would retrieve files from trashed file systems, but at the point I was looking, there were not any that would do that for ext4 file system files.

[RobHenry]

Just had a look through your previous thread as you suggested. I don't know what NOOBS does when it starts installing Arch but it seems logical to assume it drops and creates partitions to hold the OS. If you can create partition #6 with .the same size and offset as it had before then you will probably find that all your data is intact.

Have a look at testdisk, which is designed to recover lost partitions and deleted files: http://www.cgsecurity.org/wiki/TestDisk

Good luck

[DougieLawson]

It doesn't matter what you select from the recovery menu, installing anything (Arch, Raspbian, OpenELEC) will start by trashing everything that's already installed on the SDCard.

Arch is no longer in NOOBS. But, in this case it's not to blame anyway.

Once you've used NOOBS to complete any OS installation, you can't add anything more to that SDCard. You can only use it as a boot manager to chose between installed OSes.

[rPioneer]

@Dougie, I understand that, but I wanted to know what Arch/NOOBs actually does to the card when it begins installing.

@Rob That sounds like a good idea. But how would I actually make the partition, and in the correct place on the card? UPDATE: Silly me didn't re read your post before replying! I'll have a look at testdisk.

[gsh]

When you try to recover using NOOBS the first thing it does is wipe the partition structure completely and recreate it from scratch with new offsets. It then formats those partitions (as indicated by the partitions.json file) and copies the Arch sources from the .tar.gz to each of the partitions defined

Finally it does some post configuration (such as setting up the /etc/fstab file correctly)

So, when it comes up with the warning saying this is going to wipe the whole thing and replace it, it wasn't lying!

Gordon

[RaTTuS]

when you install another thing [arch raspbian, openelc etc] then it will overwrite the partition with a new image
stopping this part way though will leave it in an unknown state

best bet is to go back to your backup

[rPioneer]

So it may have destroyed the partition structure, but surely a format would take a long time, so it has not neccesarily deleted my files?

So my files may still be there but the partition that hold them is damaged/non existant? Bear in mind I still have a very limited knowledge of how SD card partitions work!

[fruitoftheloom]

The only to find out how much damage you have undertaken is to use a File Recovery program, anything else is conjecture and supposition

TestDisk was mentioned in an earlier response.....

[rPioneer]

I'll give testdisk a go. Thanks folks!