I have mistakenly used my (btrfs) /home Linux partition for the installation of FreeBSD, and it was overwritten by the UFS filesystem. Now this UFS-formatted and written partition is not even readable by Linux, as it refuses to be mounted, I don't understand why. The error message when trying to mount it is:

Error mounting /dev/sda2 at /media/adfa/59ed656a78c3231b: Command-line `mount -t "ufs" -o "uhelper=udisks2,nodev,nosuid" "/dev/sda2" "/media/adfa/59ed656a78c3231b"' exited with non-zero exit status 32: mount: /dev/sda2 is write-protected, mounting read-only
mount: wrong fs type, bad option, bad superblock on /dev/sda2,
missing codepage or helper program, or other error


Anyway, most probably I should not even be trying to mount it the normal way, because I don't want to read it as UFS.

What I need to use is a recovery tool which supports btrfs, but I don't know what to use.

I am sure that the partition was only partially overwritten (because it is over 300 GB, and the FreeBSD installation is much smaller), and I wish to recover at least some of the files, even if I have to do it manually (i.e. by searching for specific strings through raw data).

Can you please help me?

Begin to make a raw copy of it to work on and try recuperation tools like testdisk. The idea would be to force the FS to be seen as BT instead of UDF, perhaps that you'll need to manually edit the first sector??? Good luck...

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As suggested, testdisk, and its associated program photorec, is the often recommended way of recovering any still useful files. The website has several pages that are useful, including pointers as to how to scrape data from any recovered files to attempt to give them meaningful names.

You might also spend some time on the btrfs wiki - the restore command would be a good start. I've not tested it personally.

I have not tried testdisk yet, but from what I have read online it only recovers files, and ignores directory structures.
Do you think that any other tool (maybe one of the Windows-based payware tools) may be able to recover both files AND directory structures from a damaged Btrfs partition?

duplicate of https://www.linuxquestions.org/quest...gs-4175616189/
There is no such thing "raw filesystem".
You need to create a copy of that partition (for example with dd) and you can analyze that copy. I don't really know if you can force to use it as btrfs or ufs, and also be able to find anything. As far as I heard testdisk is a really good tool to recover (files).
https://en.wikipedia.org/wiki/Btrfs here you can find a few words about btrfs-restore, but I have never tried that.

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Testdisk can only deal with what it has - overwriting the beginning of a "normal" filesystem (say ext4) wipes out the inodes with all the directory/filename info. It is no more.
btrfs is different in structure, but I'd be guessing - as the wiki says, get on irc and talk to people that know.

I trust you have noted my sigline.