Formatting a Drive With Hidden Partitions

Issue/Question

I have an external storage device (ie: flash drive, external hard drive, etc...) that is not showing the full disk size, even after formatting the device using Disk Utility. 

Environment

• macOS

Cause

The external device might have been pre-configured with special software on a partition that was made for a machine operating with Microsoft Windows only, thus not being seen by macOS.

Resolution

 Note: This process will delete everything stored on the device. Only proceed if you do not need any files that are currently on the device.

1. Plug the device into your computer. 
2. Open the Terminal program. 
3. Type in the following command:

     diskutil list  

4.  On the keyboard press: Enter
5. The drives that your computer can find will be listed; find the drive that you wish to format and make note of the name, such as disk2.
6. To erase the entire drive and make it one partition, enter the following command:

     diskutil eraseDisk JHFS+ Test /dev/name of disk from step 4

7.  On the keyboard press: Enter
8. The drive will be formatted from multiple partitions to one partition; you may close the window once the process states that it is finished. 
9. You may begin using the drive. If you would like to further format the drive for other purposes or tasks, please follow this article.