skiVT-100, thanks ! I have streaming video now 8)
A flash drive to the usb port or even behind a hub is all the same, it is /dev/sda1
So I have a webcam plus flash drive connected to a hub.
I didn't know which is the newest software source folder, so I took the newest folder that had 2014 packages, and it worked.
Running mjpg-streamer was all that was needed, and using port 8080 in my browser.
Update: The Yun shield uses RX and TX to communicate with the Arduino board. When using an Arduino Mega, the usb-serial has to be disabled to make the Yun Shield work with the Arduino Mega. So only the Leonardo is the most useful board for the Yun Shield. The Dragino firmware is not very stable. I have to reset it to factory defaults sometimes, or force to re-install packages. The shield requires knowledge of Arduino and linux. If you can get it for about 26 euros inclusive shipping (like I did) you get great value for money. Search on Ebay for : yun shield arduino
It can run a webserver with control by/to the Arduino board, and many more internet applications like a webcam stream. They will run at the same time if you want to. The components don't get hot. For many projects it is a good (or even a better) alternative for the Raspberry Pi.
Update 2: Streaming two webcams via wifi; using a usb flash drive; playing mp3 files (or internet radio) to a usb-audio device, and a webpage controlled by the Arduino board with zepto.js; also having the LuCI interface open, and the SSH telnet. Everything at the same time, and the cpu is at 80% busy ;D