Formatting a drive so you can install and boot macOS requires the GUID partition map. Unfortunately, Disk Utility in macOS High Sierra doesn’t make that option easy to find. Read on to see where it’s hiding.
We’ll use an external drive for this example. Start by connecting the drive to your Mac. Once it’s mounted, launch Disk Utility. The app is hiding in the Utilities folder inside the Applications folder.
Click the View widget in the upper left corner of the Disk Utility window and choose Show All Devices. Now you should see your drive device descriptions with the drive name nested underneath. Select the drive description just above the drive name for the device you want to format.
Now click the Erase tab. Set the format to Mac OS Extended (Journaled) and the Scheme to GUID Partition Map. If you selected the drive name instead of its description you won’t see the Scheme option.
Click Erase to wipe all the data that’s currently on the drive and reformat it for your macOS install. The drive will be formatted HFS+, but installing macOS High Sierra or Mojave will change the format to APFS, assuming you’re installing on an SSD.
I did this as you stated on an internal drive of a 2017 iMac, booted from a temp Mac OS High Sierra on an external drive. The internal drive got corrupted during an attempt to upgrade to Big Sur (from High Sierra and is formatted as APFS). Everything was previously saved by Time Machine onto another partition on the external drive. Doing what you suggest in the article Disk Utility just hangs with the msg ‘Erasing (“drive device description”) and creating “iMac Hardrive”, Nothing shows in the window after many minutes, with the progress bar showing nothing happening. Now what? Is the internal drive dead?
Thank you, thank you, thank you! I recently upgraded to Catalina, and needed to reformat an external drive to APFS for my backup software to work with it. The partition command was grayed out, and I couldn’t for the life of me figure out why. Clicking View and selecting Show All Devices allowed me to see the drive I needed to convert.
THANK YOU!!!
i was having an issue but everywhere else i looked left out “show all drives.” that small step was all i needed to fix my issue thanks again
Jeff,
Thank you for this information. Like others, I spent a good amount of time chasing this down before finding your post. One would think that Apple would have this information noted someplace easily found. Good job!
Regards,
Andy
Thank you for this priceless tip. At last I found out about this extra layer of Apple Disk Utility being able to set GUID table on an SD-Card or USB stick. At last my MacBook Pro 7.1 mid 2010 is creating a bootable external drive with “Install macOS High Sierra” from the App Store, so that I can upgrade the internal disk to WD Blue 250GB SSD and make this machine whizz along with LibreOffice.
thank you
Thank you so much Jeff Gamet! I spent a good hour combing the internet and finally found this site and the tip you gave on how to get the scheme to show up via the view button really saved my hide on this one. Thanks again!