Disk Utility won’t erase the USB flash drive (“Couldn’t open device”)

disk-utilityhard driveusb

I am willing to dual-boot my MacBook Pro (13-inch, Early 2011) macOS Sierra to install Ubuntu.

I am having some trouble with my USB flash drive when I try to erase it using Disk Utility. It says:

Erase process has failed. Click Done to continue.

Unmounting disk
Couldn't open device.
Operation failed…

Erase process has failed. Click Done to continue. Couldn't open device.

Best Answer

Open Terminal, and type 

$ diskutil list
/dev/disk4 (external, physical):
#: TYPE NAME SIZE IDENTIFIER
0: FDisk_partition_scheme *8000.1 GB disk4
1: 0xEF 12.3 MB disk4s2

It cannot display the USB. To erase the USB completely, run:

$ diskutil eraseDisk free EMPTY /dev/disk4
$ diskutil list
/dev/disk4 (external, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *8.1 GB disk4
1: EFI EFI 12.3 MB disk4s1
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