Linux Trick 1: Unmounting the unresponsive DVD drive in Linux

The newbie states that when he pushes the Eject button on the DVD drive of a server running a certain Redmond-based operating system, it will eject immediately. He then complains that, in most enterprise Linux servers, if a process is running in that directory, then the ejection won't happen. For too long as a Linux administrator, I would reboot the machine and get my disk on the bounce if I couldn't figure out what was running and why it wouldn't release the DVD drive. But this is ineffective.
Here's how you find the process that holds your DVD drive and eject it to your heart's content: First, simulate it. Stick a disk in your DVD drive, open up a terminal, and mount the DVD drive:

# mount /media/cdrom
# cd /media/cdrom
# while [ 1 ]; do echo "All your drives are belong to us!"; sleep 30; done
 
Now open up a second terminal and try to eject the DVD drive:

# eject
 
You'll get a message like:

umount: /media/cdrom: device is busy

Before you free it, let's find out who is using it.


# fuser /media/cdrom
 
You see the process was running and, indeed, it is our fault we can not eject the disk.
Now, if you are root, you can exercise your godlike powers and kill processes:


# fuser -k /media/cdrom
 
Boom! Just like that, freedom. Now solemnly unmount the drive:


# eject
 
fuser is good.