"You may not install this volume because the computer is missing a firmware partition.

Do you have a working internal drive properly partitioned and formatted for use by macOS? If not, then you cannot install macOS 10.13+ because the bundled system firmware updater will fail because the macOS installer/system firmware updater requires a properly partitioned and formatted internal drive.

You may need to Format the new Disk to MacOS Extended Journaled.

ky151 wrote:

I have a 2-partitioned drive of 500GB each, both are formatted with MacOS Extended (Journaled). My iMAC is Model 11,2 (2010) and currently runs under Serria version 10.12.6 on one of the partition.

I have also received the same error "You may not install to this volume because the computer is missing a firmware partition" when I tried to install MacOS High Serria version 10.13.x. Pls advice.

The only time I've seen this error is when an internal drive is missing or not properly partitioned or formatted for macOS or when a third party PCIe SSD is used internally. Make sure the internal drive has a GUID partition and at least one MacOS Extended (Journaled) volume. If it does, then run Disk Utility First Aid on the drive and the volume to make sure there are no errors reported. Even if First Aid reports no problems, then maybe there is still an issue due to the two volumes. You may need to backup both partitions and erase the whole drive and recreate the two partitions and restore from your backup. Then see if you can perform the OS upgrade.

Or maybe you have some third party software which is interfering. You may want to try booting from Internet Recovery Mode (Command + Option + R) or by creating a bootable macOS 10.13 USB installer.

Yes, my current MacOS (Serria 10.12.6) was booted from an external drive. I have erased my entire drive (external) without partition and used MacOS recovery. Everything is well back on Serria, but I still failed to install H-Serria with the same "missing a firmware partition" msg. Believe it was due to my boot disk is being external drive.

I have followed your above link to create a bootable macOS 10.13 SB installer so that the H-Serria installer can installed from the Application folder. However, I got the disk format error as below.. what shall I do from here ?

I have a 2-partitioned drive of 500GB each, both are formatted with MacOS Extended (Journaled). My iMAC is Model 11,2 (2010) and currently runs under Serria version 10.12.6 on one of the partition.

I have also received the same error "You may not install to this volume because the computer is missing a firmware partition" when I tried to install MacOS High Serria version 10.13.x. Pls advice.

unfortunately my iMac was downed with its internal drive and currently system is booted with Serria from external drive only.

noted the “constraint” that High Serria requires proper internal drive partition and format to be installable.

Thanks for the root cause confirmation.

BDAqua wrote:

You can Install High Sierra to an external drive.

Since macOS 10.13+ include a system firmware updater, the macOS installer/firmware updater requires a working properly formatted internal drive to work (at least if the system firmware needs updating). I don't know if the same error happens when the system firmware is already updated (never had the time to test it). @ky151 confirmed the internal drive is not working so that is why @ky151 is getting the "missing firmware partition" error message when installing macOS 10.13+.

However, looking closer at @ky151's last post with the screenshot I see @ky151 is also having trouble creating the macOS 10.13 USB installer probably because of an issue with the USB drive.

Any luck?

You can Install High Sierra to an external drive.

Ah, thanks.