How to Encrypt Mac External Drive aka Fix “A GUID Partition Table (GPT) partitioning scheme is required” Error
Are you banging your head trying to figure out what the “A GUID Partition Table (GPT) partitioning scheme is required” error means or how to fix it? I was – here’s the quick fix. It’s easier than you think.
Watch the video to see how to fix the problem:
What causes the error?
The root cause of this error is because the drive you have purchased does not come set up with a “GUID Partition Map” from the factory. In order to fix this, you have to change the partition map type to GUID.
The image to the left shows the 3 options you can select from when erasing the drive and re-doing the partition map.
As you can see in the image, the “GUID Partition Map” is selected. That is because I have erased the drive and changed the partition map.
How to Fix the “A GUID Partition Table (GPT) partitioning scheme is required” Error
You need to use “Disk Utility” (which is a program that comes with your MacOS) to change the partition map type to “GUID Partition Map” via the “Erase” function.
IMPORTANT: Before you do this, make sure you have a backup of the drive contents if those contents are important to you.
To do this, open the Disk Utility application. It is located in: Applications -> Utilities -> Disk Utility
When it opens, two-finger click (or right click) on the top-level aka the “physical drive” for the drive you want to change. It will then show you a menu such as the one on the left.
From this menu, you want to select “Erase.”
Then you will be presented with another menu as described above, and shown here to the right. On that menu, you want to select “GUID Partition Map” in the “Scheme” drop-down selection.
You can also change the “Format” selection to use one of the encrypted types. Or you can choose to encrypt it later by two-finger (or right clicking) the drive in a finder window and selecting “Encrypt” and completing the process that way.
I hope this helps! Once I figured out where to change the partition map type, it was easy and I had no problem encrypting all 4 of my new drives very quickly.