How to Create `sys-usb` in Qubes OS Installed on an External USB SSD Without Breaking the System

[apparatus]

Check if you have multiple USB controllers and they are available on the physical USB ports. If you have them then you can dedicate one of the USB controllers to dom0 and connect your USB disk to it.
Run this command in dom0 to see if there are multiple USB controllers available:

lspci | grep USB

Then check if there are different USB controllers connected to the different USB ports:

Quick script to add BDF to lsusb output to find controller for devices on KVM/HUB

For what it may be worth to others, I became sick of using a manual process to find the PCI controller (BDF) associated with a USB device that is connected via an internal or external hub, including those in a KVM The below script should work as-is and will add an additional field to the output of lsusb that provides the BDF for the device - it will be the actual PCI controller that the device ultimately connects to the system through This is most useful when working with a fresh install on ne…