Shared folder as stated in laebshade's and Alvin Sim's answers. This operation is equivalent to physically inserting your USB key in a USB port of your guest machine.
In your VirtualBox window select the "Devices => usb devices" menu item on the top left guest window menu and select your USB key. Whenever you insert an USB key, if you want to see it in the guest proceed as follows:Ĭleanly unmount the USB from windows by clicking on the corresponding icon in the bottom right corner and selecting the "safely remove. From your question I imagine you run Ubuntu in a guest and the host is Windows.
In any case, you can easily make the USB key visible in the guest. You shall find your stuffs in this GUEST_SHARE folder. sudo apt-get install virtualbox-guest-utils If you see the error mount: wrong fs type, bad option, bad superblock on …, this means you first need to install virtualbox-guest-utils. In Guest terminal, type sudo mount -t vboxsf HOST_SHARE GUEST_SHARE`
Though it is clear, I still spend some time to do everything correct.