In Qubes Beta 3 a new tool, ```qvm-block``` has been introduced that makes mounting USB devices to any user AppVM very easy, no matter which actual VM is handling the USB controller (those can be assigned using the [qvm-pci command](/wiki/AssigningDevices)).
In order to assign a USB disk to a VM, follow these steps:
> This will list available block devices connected to any USB controller in your system, no matter in which VM this controller is hosted. The name of the VM hosting the USB controller is displayed before the colon in the device name. The string after the colon is the name of the device used within the VM.