A lot of well-meaning people dumped their leftovers on me when I mentioned I was using a machine with a floppy drive, and had use for some spares. The things are like coat hangers now though — I have about twice as many as I wanted, and 10 times more than I need.
I also don’t really want to know what was on the floppy before it became mine, so I scrounged around a bit and found this as a command to overwrite the disk, until I find time to actually use it. As an alternative to the
shred command. ...
dd if=/dev/urandom of=/dev/fd0
The drive assignment is for Debian there, so it might be different for your distro. And changing the destination assignment will work for a USB drive or something else too. My primary school maths teacher taught us that we should always check our work, so ...
dd if=/dev/fd0 count=1 | hexdump -C
That gives you a quick look at the earliest part of the floppy, so you can check and make sure what's there is more or less unreadable. I don't know if it's a terrifically secure method or proof against forensics efforts, but neither of those is really a concern for me. :)