After some research, I’ve learned that Volumio uses usbmount to automatically mount USB drives. I have moved my root partition to a USB hard drive that is always plugged in, so I don’t want it mounted at /USB. I occasionally plug in flash drives, and it’s convenient to have them mounted at /USB. How can I exclude one specific drive from usbmount?
So far, this hasn’t caused any problems, but it seems very strange, having /dev/sda1 mounted in two locations (/ and /USB).