Question: I want to do the update to the latest version of Mac OS X Sierra.When I launch the update I get following error message:

This Disk doesn’t use the GUID partition Scheme

Use Disk Utility to change the partition Scheme.

Select the disk, choose the Partition tab, select the Volume Scheme and then click Options.

It is a 2012 MacBook Pro. The original HDD was replaced with a new SSD drive a few month ago. To do the replacement, I used Super Duper to clone the 2 drives.

When I do diskutil cs list, I get

No CoreStorage logical volume groups found

When I do sudo gpt -r show /dev/disk0, I get

start ?size ?index ?contents

0 ?1 ?MBR

1 ?1

2 ?976773166 ?1 ?MBR part 175

What should I do?

Answer: In Disk Utility, near the close/minimize/fullscreen buttons, you can see a “View” mode dropdown menu. Set the view mode to “Show All Devices”, then you’ll see the “root” drives. Click on a root drive, and then click on the “Erase” button. Now an option to change the “Scheme” from Master Boot Record to GUID appears in the Erase subwindow.