I used external floppy USB drive on my Linux box. It calls UFI device. A UFI Device is a removable-media mass storage subsystem, which connects to a Host computer via its Universal Serial Bus (USB) port. The Host and UFI Device communicate by exchanging Command Blocks, data, and status information. The method used to transport this information over the USB is defined by the Bulk-Only or CBI transport specifications. This specification defines the UFI Command Set, which was designed to interface Floppy Disk Drives to the USB. The “USB Floppy Interface” (UFI) Command Set is based on the SCSI-2 and SFF-8070i command sets.
Other words, Linux normally works with such floppy disk. But Linux doesn't support floppy format for such devices. So, if you need format floppy, you have to install the special utility which support UFI Command Set. So, finally to say - setup UFIformat utility. It is console based utility. Run it as:
# ufiformat /dev/sdaAnd do High-level formatting by:
# mkfs.vfat -I /dev/sdaAll should be done by this.