If you ever need to know which application(s) are using (writing or reading) a given directory on your disk, lets say because it is a usb memory stick that you need to unmount and you cant because you do not know which application is still using it.
And the Operating system says that the unit is busy
This is what happens when I try to unmount it
sudo umount /media/usb
umount: /media/usb: device is busy
Use this command.
lsof +D /media/usb
This is the output for me.
COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME COMMAND PID USER FD TYPE DEVICE SIZE NODE NAME bash 5581 ggarron cwd DIR 8,49 32768 1 /media/disk/ evince 6991 ggarron 15w REG 8,49 1496960 323 /media/disk/BA1000_MSAG Brochure_Spanish.pdf
This is because I cd to /media/usb/ from another terminal window, and also opened a .pdf file.
So you can see that bash and evince are using that directory, now I can close or kill them, and I will be able to unmount the usb memory.