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qemu usb storage emulation
QEMU has three devices for usb storage emulation.
Number one emulates the classic bulk-only transport protocol which is
used by 99% of the usb sticks on the market today and is called
"usb-storage". Usage (hooking up to xhci, other host controllers work
qemu ${other_vm_args} \
-drive if=none,id=stick,file=/path/to/file.img \
-device nec-usb-xhci,id=xhci \
-device usb-storage,bus=xhci.0,drive=stick
Number two is the newer usb attached scsi transport. This one doesn't
automagically create a scsi disk, so you have to explicitly attach one
manually. Multiple logical units are supported. Here is an example
with tree logical units:
qemu ${other_vm_args} \
-drive if=none,id=uas-disk1,file=/path/to/file1.img \
-drive if=none,id=uas-disk2,file=/path/to/file2.img \
-drive if=none,id=uas-cdrom,media=cdrom,file=/path/to/image.iso \
-device nec-usb-xhci,id=xhci \
-device usb-uas,id=uas,bus=xhci.0 \
-device scsi-hd,bus=uas.0,scsi-id=0,lun=0,drive=uas-disk1 \
-device scsi-hd,bus=uas.0,scsi-id=0,lun=1,drive=uas-disk2 \
-device scsi-cd,bus=uas.0,scsi-id=0,lun=5,drive=uas-cdrom
Number three emulates the classic bulk-only transport protocol too.
It's called "usb-bot". It shares most code with "usb-storage", and
the guest will not be able to see the difference. The qemu command
line interface is simliar to usb-uas though, i.e. no automatic scsi
disk creation. It also features support for up to 16 LUNs. The LUN
numbers must be continuous, i.e. for three devices you must use 0+1+2.
The 0+1+5 numbering from the "usb-uas" example isn't going to work
with "usb-bot".
Gerd Hoffmann <>