to flash it to a usb drive. I hadn't realized the system had reassigned hard drive device ID from the previous day, and for about 3 seconds it executed before I terminated the process once I realized what I did.
I immediately created a disk image of the Data-Destroyed hard drive just in case I screwed something up in trying to recover it.
I ran testdisk, but I'm not really sure how to use it or how to try to recover the data. The drive mounts okay, and shows it has 19,336 items totalling 8.2 GB of the Debian system files.
The files that were overwritten in the first 3 seconds are gone. Though, It's likely that most, if not all the data is okay. Hopefully its just the pointers to the files that was over written, meaning you'll have to use some file recovery software on the disk/image to get it back. I don't have any software suggestions to do that.
Yeah that's the first thing I wrote in my notes, to stay far far away from dd.
Ventoy isn't in the Debian repos, but I did find a similar program there - Gnome multi writer. I've used unetbootin in the past on Ubuntu, but Debian instructions specifically say not to use a program like unetbootin for some reason. I'll give the multi writer a shot the next time I do a fresh install, thanks for the tip!
Ventoy isn't something you need to install on your system. It's a boot loader that gets installed on a flash drive. You can just copy ISO files to the flash drive and pick which one you want from the boot menu.
MultiWriter is basically just doing the same thing dd does, but with a GUI.
Phtorec can scan the drive and try to recover your remaining data. I've used it in the past to get files back from dying drives. Linky https://www.cgsecurity.org/wiki/PhotoRec
A time machine barring that the data DD overwrote is gone. there are some theories around being able to recover things with an electron microscope but eh. You could repair the partition table and see what you can get back but its best to consider the data knackered.
Sorry probably not what you want to hear but it is what it is.