# umount /media/disk/
umount: /media/disk: device is busy
# fuser -m /dev/sdc1
/dev/sdc1: 538
# ps auxw|grep 538
donncha 538 0.4 2.7 219212 56792 ? SLl Feb11 11:25 rhythmbox
http://ocaoimh.ie/2008/02/13/how-to-umount-when-the-device-is-busy/