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What type of format does Fedora media writer do?

asked 2017-06-30 09:52:37 -0500

Wastrel gravatar image

Hi I recently was attempting to create a Fedora Live USB boot disk. Unfortunately I had my 2 TB external harddisk also connected at the time and inadvertently started the process on that instead of the USB drive intended. I clicked cancel as soon as I realized but now the drive is not recognized. My question is what sort of format does Media Writer do? Is everything lost? I have tried testdisk which upon first analysis (using an Intel structure) finds invalid FAT boot sectors: 0 D FAT16 >32M 95867 252 19 283476 201 41 3013935395 0 D FAT32 261753 232 23 364762 75 24 1654829696 neither of which can be recovered. I was pretty sure the original drive was an NTFS system. I am hoping that I have not lost all data on the 2TB system and rather only 2GB may have been possibly overwritten. Is there a way to restore the partition table to the original NTFS system or is my only option doing a raw recovery where all the file names and folder structures are lost? Or even worse a full-format was performed and I have lost all the data?

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villykruse gravatar imagevillykruse ( 2017-06-30 13:40:23 -0500 )edit

Hello villykruse, I've seen that post and decided to ask my question as the answer to how fedora media writer does its formatting was not addressed in that post.

Wastrel gravatar imageWastrel ( 2017-06-30 14:33:15 -0500 )edit

Is my understanding that Media writer partition and format the disk to FAT since is what USB media boot. So you may have lose all your partition information.

aeperezt gravatar imageaeperezt ( 2017-06-30 21:40:05 -0500 )edit

Run

sudo file -s /dev/sdb

and it will tell you which partition format is found on /dev/sdb.

villykruse gravatar imagevillykruse ( 2017-07-01 01:37:05 -0500 )edit

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answered 2017-07-01 02:56:52 -0500

muep gravatar image

My impression is that the media writer basically just copies a pre-built disk image to the beginning of the USB storage device that you point it at. Thus you might have quite a lot of data in the disk, ideally losing only the items that had happened to get allocated by NTFS to the beginning of the available storage area.

There is a nice article about how the Fedora live disk images are set up. It is a bit old by now, but I think the description is still mostly valid. It has quite many technical details in it but the main thing to note is that the image has been specially set up to seem like a valid boot medium for many different kinds of things that can boot some sort of a disk image. I'd not be surprised if this can confuse some data recovery tools.

The answers to that other question suggested by villykruse seem quite promising with regards to data recovery being able to handle this exact case. Hopefully they will help!

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Nice find.

villykruse gravatar imagevillykruse ( 2017-07-01 03:47:59 -0500 )edit
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answered 2017-07-02 15:40:53 -0500

cmurf gravatar image

Media Write uses the functional equivalent of dd on all three platforms. So it's just doing a block copy from the image file to the chosen device. This will instantly obliterate a conventional MBR, whereas a GPT has a backup header+table that will still be intact. But the bigger problem is that within seconds the first data partition, file system volume signature and super block, and critical file system metadata is already being overwritten. It's definitely a scrape operation, at best, to recover user data. There's no chance an fsck will fix this. Nevertheless I filed a feature request. https://bugzilla.redhat.com/show_bug....

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Asked: 2017-06-30 09:52:37 -0500

Seen: 836 times

Last updated: Jul 02 '17