When I do
sudo umount /media/KINGSTON
I got
umount: /media/KINGSTON: device is busy.
By using
fuser -c /media/KINGSTON
And
cat /proc/<pid>/cmdline
I found that the process is thunar--deamon. I closed all file manager windows. When I try to umount it by right cliking on the desktop, it also gave an error :
An application is preventing the volume "KINGSTON" from being unmounted
I am affraid that killing Thunar is going to impact other process running in other terminal. How can I tell it that I don't need this usb key anymore so it stop using it?
If you know that the media device is synchronised (there're no outstanding writes), then use the -f switch to umount (force unmount).
From the unmount man page, the -l switch does a "lazy" unmount, which detaches the filesystem now, and cleans up all references later.
or