This is the recommended method because it the donkeys i like the way you walk should always fix the error.
Click Done to continue.
If the Unable to Unmount Error is triggered by first aid or formatting a non-boot partition, you may be able to fix the error by booting from the Recovery partition that is included with all new versions half life 2 episode 4 of.
OK, weve tried to be nice, but is the disk still not letting you work with it?If you have used our method above to create a bootable installer, choose Disk Utility from the available menu.This should force erase the entire physical disk and all its related volumes, then create a single Mac OS Extended (Journaled) volume: 3) Hopefully you can now perform your desired erase, partition, installation or deployment on this drive.Couldn't unmount disk, then you may have to force an unmount through the terminal.Note: Use of the sudo command may not be necessary for some of these actions, however, as long as you know the administrator accounts password, starting any unix command with sudo will force the command to be run as the unix root user, so you.You can then run Disk Utility from there.Before you trash your drive, it is also worth restarting the mac.For a single drive system this will probably be disk0 : 2) Now enter the following where x is your disk identifier: sudo diskutil unmountDisk /dev/diskx 3) Press return.You should also see the name of the disk such as Macintosh.
Still unable to work on the disk?
Run a command similar to this one sudo diskutil unmountDisk force /dev/disk2, if you're prompted for a password, enter it (yes, your account does need to have administrative privileges).Erasing a "WD My Passport or My Book Media".This should force unmount the volume: 3) Attempt again to perform whichever task caused your Couldnt Unmount Disk error.Now perform the original task that threw the Couldnt Unmount error.Go to First Aid to verify and repair the disk, or go to Erase to format the disk.If you have created your own bootable drive with a full system, open Disk Utility from /Applications/Utilities.Hold down the option key during boot, then select the attached boot drive (typically has an orange icon at the boot menu).You should see some disks appear like /dev/disk0, /dev/disk1, /dev/disk2.