Can't format USB drive

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http://askubuntu.com – I have a 4 Gig USB drive that I'd like to format. I go to the Disk Utility, and try to format it, but it says that the device is busy. (This same error occurs no matter whether I tried to format the whole drive, or just the partition.) So, I do some research, and figured out how to disable automount. It's now disabled. To be on the safe side, I first unplug then reconnect the USB stick then tried: sudo umount /dev/sdb sudo umount /dev/sdb1 sudo umount /dev/sdb* Now, the Disk Utility STILL gives me the same error - usually "/dev/sdb is busy" or "/dev/sdb1 is mounted" or similar. (HowTos)