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allows CDs to eject even if apps are still open from the CD
Unmount hard drives in a NetBoot client machine.
Get rid of DMG automatically when unmounting disk images.
Just another GUI for diskutil to mount / unmount volumes.
If partitioning a drive with Disk Utility gives you unmount or resource busy errors, there may be workarounds you can use.
Some people have noticed an issue in Snow Leopard where iTunes will query for Audio CD track information and then promptly unmount the CD from the system.
Apple: Improper unmounting can cause disappearance of files in Mac OS X 10.4.x
Mac OS X 10.4.4 Special Report: Acard-connected drives unmountable, other issues
Mac OS X 10.4.4 (#11): Acard-connected drives unmountable, other issues; Fujitsu MO drives -- attaching to a hub; more
FireWire-based RAID arrays spontaneously unmounting
Mac OS X 10.4.2 Special Report: FireWire Drives spontaneously unmounting
Mac OS X 10.4.2 Special Report: FireWire/USB volumes refusing to unmount
Devices refusing to unmount: Force quitting the Finder may resolve
More on drives refusing to unmount; solution from Symantec