external hard drive still shows in disk utility after it was removed I unmounted and removed my backup disk called TimeMachine, but it still shows up in the disk utility app. 

I tried running 

$ diskutil unmount /dev/disk3s2


and 

$ diskutil unmountdisk /dev/disk3


but it didn't help. 

How can I make it stop showing in the disk utility? 

￼￼
The correct command is given below.

diskutil eject disk3


You can also use the Finder and Disk Utility applications to eject a drive.

Occasionally, you may be using a drive that is not fully Mac compatible where the above command does not work. For example, I have an mp3 player that is not Mac compatible. When diskutil eject command is used, the player ejects only to remount a few seconds later. So, before removing the player from the USB port, I have to log out of my account to make sure all files are closed. In your case, you may have to shutdown the Mac before removing the drive.