If you use Linux as Desktop or even on some servers you might end up in situation where mounted filesystem is refusing to unmount with an error:
umount: /media/cdrom: device is busy
That's pretty annoying and many people (especially) desktop users would force a system reboot in order to have the fs unmounted.
If this happened to you, there is no need for that anymore. umount cmd has a handy option – (Lazy Unmount) for situations like this. Here is -l description from umount manual:
-l Lazy unmount. Detach the filesystem from the filesystem hierarchy now, and cleanup all references to the filesystem as soon
as it is not busy anymore. (Requires kernel 2.4.11 or later.)
So next time you hit "umount device is busy" do:
# umount -l /media/cdrom