Sometimes a Disk Utility Error Message flags up when formatting or partitioning in Mac ( Mac Book Pro, iMac, Mac mini, Mac Pro, MacBook Air) which is asymptomatic of the HardDrive already engaged in operation and needs to finish before processing the next command to get past this we would need to forcibly unmount external hardDrive in Terminal by inputting some commands. See video which exemplifies how Terminal is initiated and the commands are applied to forcibly unmount the Drive which debugs the error message to zero errors and zero warnings.

CODE inputted in Terminal: Step 1: diskutil list Step 2: diskutil unmountDisk force Step 3 /Dev/ Disk 2,3,4,5 which is a variable.

Type in

terminal
spacebar diskutil spacebar list
(just take note of " /dev/disk2 " and dont type in just yet - depending on what your external hard drive references , in my case its disk 2 in yours could be disk3, My WD elements is the second disk)

now continue typing in

clear
diskutil spacebar unmountdisk spacebar force spacebar /dev/disk2
hit enter on your keyboard

Click the links below for use tips on how to

How to Format, Partition, Troubleshoot & TimeMachine Backup External HardDrive for Mac & Windows(ExFat or MS-Dos)
[ Ссылка ]

How to Partition & Time Machine Backup External HardDrive for Mac & Windows OS's (ExFat or MS-Dos)
[ Ссылка ]

How to troubleshoot and unzip or expand your zipped files with the error message "unable to expand photos (Error 1 - operation not completed)"
[ Ссылка ]

How to format your External HardDrive and set up time machine to backup Mac
[ Ссылка ]

How to Troubleshoot error message operation failed when formatting and partitioning HardDrive
[ Ссылка ]

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