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Disk doesn't use GUID Partition Table scheme

I have read through many different 'answers' to this on the Support site, and none of them address my issue, so please read and help. I bought a new 2TB SSD external, and I want to install macOS High Sierra on it. (this mid 2010 iMac I'm using won't install anything higher). So, step 1, format the SSD to mac OS Extended Journaled (because it came to me FAT32 MS Dos. ) Done. Step 2, get the High Sierra installer onto my iMac. Done. Step 3, run the installer and try to choose the SSD. It's grayed out, and the reason given is "This disk doesn't use the GUID Partition Table Scheme. Use Disk Utility to change the partition scheme. Select the device containing the disk, click the Erase button, select the Volume Scheme and then click Erase." Well, friends, this works just fine but there is Nothing about a Partition, and the button for partition is grayed out. Tried it anyway. Same result.

Okee dokee, let's use restore. I clicked on my SSD in Disk utility, and clicked Restore. the source is Macintosh HD. The error says "Can only be done on GPT partition maps."

Dead end everywhere. How can I make my new, fast SSD my boot and start-up disk, and let the iMac run from it, instead of from the 2TB SATA hard drive?

iMac 21.5", macOS 10.13

Posted on Apr 10, 2020 7:45 PM

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Question marked as Top-ranking reply

Posted on Apr 11, 2020 3:09 PM

The InstallESD stuff is a mounted partition and usually part of a Mac installer. You can ignore that, that’ll go away when that disk image is dismounted. That’s not the volume you’re aiming at.


Partition a physical disk using Disk Utility on Mac - Apple Support

How to erase a disk for Mac - Apple Support

How to reinstall macOS from macOS Recovery - Apple Support


View > Show All Devices, then use the internal volume at the top of the list to erase and reformat and install.


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4 replies
Question marked as Top-ranking reply

Apr 11, 2020 3:09 PM in response to John Comeaux

The InstallESD stuff is a mounted partition and usually part of a Mac installer. You can ignore that, that’ll go away when that disk image is dismounted. That’s not the volume you’re aiming at.


Partition a physical disk using Disk Utility on Mac - Apple Support

How to erase a disk for Mac - Apple Support

How to reinstall macOS from macOS Recovery - Apple Support


View > Show All Devices, then use the internal volume at the top of the list to erase and reformat and install.


Apr 11, 2020 2:54 PM in response to MrHoffman

I am in SOOOO much trouble. I didn't write the whole story. I followed some YouTube instructions , and now i have a boot partition on the drive that i don't know how to get rid of . The picture i upload shows "InstallESD" as the partition. The 2nd image shows it is a UDIF read-only thingy. Am I in too deep? I want to wipe everything clean and start over.

Disk doesn't use GUID Partition Table scheme

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