Once upon a time, Ian Malone ibmalone@gmail.com said:
Thanks both, I'd thought about a USB drive, but didn't have one to hand at the time that I didn't mind messing up. The sysfs route sounds a bit safer though, and I can probably find one I don't need any more.
Another thought: use something like NBD or iSCSI running locally, rather than direct loopback volumes. I'm pretty sure you could kill an NBD or iSCSI export.