@Proxmox Host

# replace sdX with the disk device
dd if=/dev/sdX of=/root/unraid-license-usb.img bs=64M status=progress

modprobe libcomposite
modprobe usb_f_mass_storage

apt update
apt install build-essential git proxmox-headers-$(uname -r)

cd /root
git clone https://github.com/xairy/raw-gadget.git
cd raw-gadget/dummy_hcd
make KDIR=/lib/modules/$(uname -r)/build

modprobe ./dummy_hcd.ko

cd /sys/kernel/config/usb_gadget
mkdir unraidusb
cd unraidusb

lsusb
# note the physical's USB drive's Vendor and Product ID (XXXX:YYYY) and replace below
echo 0xXXXX > idVendor
echo 0xYYYY > idProduct
echo 0x0200 > bcdUSB
echo 0x0100 > bcdDevice

mkdir -p strings/0x409
lsusb -v
# note the physical's drive iSerial, iProduct, iManufacturer for the values below

echo "<<iSerial>>" > strings/0x409/serialnumber
echo "<<iManufacturer>>" > strings/0x409/manufacturer
echo "<<iProduct>>" > strings/0x409/product

mkdir -p configs/c.1
mkdir -p configs/c.1/strings/0x409

echo "Mass Storage" > configs/c.1/strings/0x409/configuration
echo 250 > configs/c.1/MaxPower

mkdir -p functions/mass_storage.usb0

echo 1 > functions/mass_storage.usb0/lun.0/removable
echo 0 > functions/mass_storage.usb0/lun.0/ro
echo "<<iManufacturer>> <<iProduct>>" > functions/mass_storage.usb0/lun.0/inquiry_string

echo /root/unraid-license-usb.img > functions/mass_storage.usb0/lun.0/file
ln -s functions/mass_storage.usb0 configs/c.1/

# unplug physical USB flash drive before the next command, otherwise duplicate IDs and serial will likely cause issues!
echo dummy_udc.0 > /sys/kernel/config/usb_gadget/unraidusb/UDC