pi@rpi /pendrive $ dd if=/dev/zero of=test bs=4M count=10
dd: opening `test': Permission denied
pi@rpi /pendrive $ cd ..
pi@rpi / $ sudo umount /pendrive
pi@rpi / $ ls -ahl
...
drwxr-xr-x  2 pi   pi   4.0K Feb 22 21:59 pendrive
...