Why Bother?
If you want to pass a USB device through to a Virtual machine, you won't want to plug the USB device directly into the host that the virtual machine is currently running on (although you can) because it will tie that virtual machine to that host. You wont be able to VMotion that VM off the host without losing connection to the USB device.
Why not just buy an off the shelf product?
Well an off the shelf Network to USB device will cost you ~£250 this will cost you ~£46 **
Examples of applications for use?
The USB management interface on a UPS or a USB software license dongle. An ASIC USB BItcoin miner could be another example.
What will I need?
A Case Any compatible case will do!
A Micro USB to USB power cable (don't buy one you'll have one kicking around)
What Next? How do I set it up?
Download the latest copy of Raspbian and follow the Instructions on how to install it on an SD card.
This guide assumes you will be connecting to the LAN via ethernet cable rather than wireless.
Once booted you can confirm the PI's IP by logging onto the console with username “pi” and password “raspberry”. Alternatively you should be able to figure out its IP by looking on your router under the DHCP server name table and connecting via putty.
Once logged in type the following;
sudo apt-get update
wget https://www.virtualhere.com/sites/default/files/usbserver/vhusbdarm
sudo chmod +x ./vhusbdarm
sudo mv vhusbdarm /usr/sbin
wget http://www.virtualhere.com/sites/default/files/usbserver/scripts/vhusbdpin
sudo chmod +x ./vhusbdpin
sudo mv vhusbdpin /etc/init.d
sudo update-rc.d vhusbdpin defaults
sudo reboot
Once it comes back up go to the Windows PC / VM you wish to map the USB device to and download run the VirtualHere USB Client
Right click USB Hubs and select "Specify Hubs ..."
Now add the IP address or Netbios name of your Raspberry PI / Network USB device. Keep the port number the same "xxxxxxxxxxx:7575"
Once discovered right click on the USB device you want to use and select Use or Auto-Use Device
Boom! That's it you're done.
Useful Links:
https://www.raspberrypi.org/help/faqs/
https://www.raspberrypi.org/documentation/raspbian/updating.md
https://www.raspberrypi.org/documentation/configuration/raspi-config.md
https://www.virtualhere.com/home
https://www.virtualhere.com/usb_client_software
https://www.virtualhere.com/oem_faq
http://vmwarebits.com/content/virtualhere-raspberry-pi-usb-server
** To support more than one USB device at the same time you will require a licence at the bargain price of £26.