maartje@Ellendig-ding:~$ sudo mkfs.vfat -F 32 /dev/sdc1
[sudo] password for maartje: 
mkfs.fat 3.0.26 (2014-03-07)
mkfs.vfat: unable to open /dev/sdc1: Device or resource busy
maartje@Ellendig-ding:~$