[Solved] Erase process has failed when formatting USB – Mac Disk utility

If you try to format a corrupted USB, Hard Disk, SSD or any other kind of storage devices using Macbook, you may receive “Erase process has failed. Click done to continue.” error message. This is most commonly because of the bad sectors or unfinished formats with the USB. The full message will be as follows.

Erase process has failed. Click done to continue.
Erasing "disk2s2" and creating "UNTITLED"
Unmounting disk
POSIX reports: The operation couldn't be completed. Invalid argument.
Operation failed.

Following is the screenshot obtained while receiving this error message.

Erase process has failed when formatting USB - Mac Disk utility

Sometimes, your USB or Hard Disk will show less size than its original capacity. You can follow the instructions below to fix this issue easily.

Why the MacBook showing “Erase process has failed. Click done to continue.” error message?

There are several factors which cause this issue to a USB or an external drive. One important reason for this issue is due to the modification of the boot drive. Personally, I had this issue because I used my USB as a boot drive. I converted the USB to a bootable macOS USB and format it on my windows PC. During the process, my USB size has reduced and when I plug it back to my MacBook, I was not able to format it again.

Also, this error may occur if any other programs are currently using your USB. Means, if you try to erase the USB in between copying or reading a file, this error may occur. Anyway, there is no particular reason for this issue. You don’t have to worry about this situation since a couple of terminal commands can fix this issue.

How to Fix “Erase process has failed” issue using Terminal Command?

You can easily fix this issue using some terminal commands. Using the terminal command, we remove the USB forcefully and do the clean format. Follow the steps below to fix this issue.

Step 1:- Mount the USB, HDD or SSD to the USB port.

Step 2:- Open the terminal. You can click on launchpad and search for “terminal” to open it.

Step 3:- Once you open the terminal, type the following command.

diskutil list

Once you enter this command, the terminal window will list all the internal and external drives connected to your MacBook. You can easily detect your target drive by looking at its size. Here I am having an issue with formatting an 8 GB USB drive and looking at the terminal list, /dev/disk2 is my target device.

Step 4:- Now copy that disk location (/dev/disk2 in my case) and type the following command in the terminal window.

diskutil unmoundDisk force /dev/disk2

replace disk2 with your own identifier.

Step 5:- No go to disk utility and select the drive you want to erase. You may not be able to erase it in FAT format. So change the option to other formats. Finally, click on the erase button.

ssd showing less capacity than original Macbook

Step 6:- It may take a few seconds to finish the erasing procedure. After that, the device will automatically get mounted to the MacBook.


There is no particular reason for getting “Erase process has failed” error message on MacBook. It may happen due to corrupted disk sectors, unfinished background processes or may be due to a bad boot sector. Whatever the reason, you can fix this issue using a couple of terminal commands. You can use the same commands if your drive is showing lesser capacity than the original capacity.

If you have any queries related to this, please feel free to comment below.


  1. Mikkel March 9, 2020
  2. Andy M. April 30, 2020
  3. Eddy Que June 28, 2020
  4. Michael Allie January 17, 2021

Add Comment