why? the data is easily recoverable.

    # dd if=/dev/zero of=/dev

now that's more like it.

dd's destruction is gated by the device's write performance and so data may be recoverable if the operation is interrupted.

For those of us with SSDs that transparently leverage AES encryption, the following generates a new keypair and marks all cells as empty instantly nuking it (and restoring the device's write performance to factory-fresh):

  # hdparm --user-master u --security-set-pass p /dev/sdX; hdparm --user-master u --security-erase-enhanced p /dev/sdX

More info on the ATA Secure Erase instruction and how to tell if your storage device supports it can be found here: https://ata.wiki.kernel.org/index.php/ATA_Secure_Erase

I read somewhere this doesn't really work anymore on common distros for reasons I don't remember. Not that I'm gonna test it.

Most `rm` impls default to `--preserve-root` now, so you need to `rm --no-preserve-root`.

it prevents against `rm -rf /`, not `rm -rf /*` does it?

Probably. The star would involve shell globbing. [edit for clarification: I meant that you’re probably right]