It would probably fail unless var was a block device actually. It wouldn’t turn a directory in to a file.

That’s why I didn’t include any privilege escalation, even if someone ran it as is it would fail. But a warning is also appropriate, thanks.

dd if=/dev/zero of=/var

But really, remove what you don’t use and/or stop using flatpak.

Full system updates without a reboot? Sign me up.

You can but unless they’re easily swapped with a ready made key it’s usually not worth the time effort and cost.