Stubborn data

Long story cut short. To reuse an SD card I had to use the linux utility “shred” on it to be rid of ghost filesystems.
However I neglected to do this for the USB drive I’m using for storage on my Orange Pi PC guineapig. Without thinking I swapped SD cards and booted it up in Armbian, forgetting to take out the USB drive which I had redone the partition table and reformatted with HForm.
Right now I’m staring at the contents of an AMD64 Ubuntu live install. Don’t forget when you want to re-use a drive for RISC OS to thoroughly destroy everything beforehand, or it’ll come back to haunt you. Things like this could easily cause data corruption. Thankfully I don’t care about the current contents of the USB drive. Wouldn’t be surprised if there is damage just from accessing it.

Why use ‘shred’? Wouldn’t it have been sufficient to overwrite it just once with zero by using dd? As far as I know, ‘shred’ overwrites several times, so using it could possibly have worn out your SD card pretty badly.

Actually, wouldn’t it also have been sufficient to overwrite the first 4MB or so of the SD card, rather than the whole thing? I remember doing that in the past to make sure that the bootloader of a previously installed OS was gone – but it’s possible that this didn’t actually work, because I don’t really know where the bootloader is stored, or if’s guaranteed to be in the same place all the time.

No offense was meant by anything I said just now.

You have a valid point. Rewriting it like that would have done the job. Makes me wonder why I did what I did. Frustration I think. In other contexts I’ve had phantom filesystems come back to haunt me causing widespread destruction, especially when the computer is trying to be clever and starts fixing what it sees automatically.