I have installed Windows 10 (in UEFI mode – no bios emulation) first on an empty SSD of an iMac (mid-2011). Once I was done I attempted to perform a usb-install of High Sierra (I have a created an HFS+ partition around 180GB or so at the end of the SSD). However the MacOS X installer for High Sierra complains that the disk in question cannot be a startup disk. Partitioning info looks like so:
-bash-3.2# diskutil list disk0
/dev/disk0 (internal, physical):
#: TYPE NAME SIZE IDENTIFIER
0: GUID_partition_scheme *512.1 GB disk0
1: Windows Recovery 523.2 MB disk0s1
2: EFI NO NAME 104.9 MB disk0s2
3: Microsoft Reserved 16.8 MB disk0s3
4: Microsoft Basic Data BOOTCAMP 322.1 GB disk0s4
5: Apple_HFS Windows Shell EFI 67.1 MB disk0s5
6: Apple_HFS MacOS 188.2 GB disk0s6
-bash-3.2# gpt -r show disk0
start size index contents
0 1 PMBR
1 1 Pri GPT header
2 32 Pri GPT table
34 2014
2048 1021952 1 GPT part - DE94BBA4-06D1-4D40-A16A-BFD50179D6AC
1024000 204800 2 GPT part - C12A7328-F81F-11D2-BA4B-00A0C93EC93B
1228800 32768 3 GPT part - E3C9E316-0B5C-4DB8-817D-F92DF00215AE
1261568 629114880 4 GPT part - EBD0A0A2-B9E5-4433-87C0-68B6B72699C7
630376448 131072 5 GPT part - 48465300-0000-11AA-AA11-00306543ECAC
630507520 367659663 6 GPT part - 48465300-0000-11AA-AA11-00306543ECAC
998167183 2048000
1000215183 32 Sec GPT table
1000215215 1 Sec GPT header
The only thing I can imagine being wrong is that the EFI partition is either too small or is not being first on the disk. If that's the case is there a way to salvage the situation without reformatting everything?
Best Answer
Your
disk0s1has nothing in it. What was suppose to go into this partition ended up indisk0s4. You can blame Microsoft for this. The Windows installer just did not make the partition larger enough. So there is two ways to look at this.disk0s1and create a new largerdisk0s2, then try to install High Sierra. I would make the EFI partition at least 209,715,200 bytes in size. If this does not work, then changedisk0s1to a EFI partition and try installing High Sierra again.I can kind of outline some of the steps, but you first would have to decide what you what to do.
Steps to merge
disk0s1anddisk0s2into a single EFI partition.You can either boot from the Windows USB installer or from the WinRE on you internal drive. In the steps below, the WinRE was used.
->Advanced options->Command Prompt.Enter the following commands. The last command lists the drive letters assigned to the volumes. In my case, the Windows volume was assigned the letter
C. If your Windows volume is assigned a different letter, then make the appropriate letter substitution in the rest of the steps.Copy the contents of the EFI volume to the Windows volume.
Remove the existing EFI partition.
Change the existing empty WinRE volume to an EFI volume. The
helpcommands were entered so selected output could be copy and pasted to aid in entering the subsequentgptandset idcommands.Copy the saved files to the new EFI volume.
Remove the files from the Windows volume and close the Command Prompt window.
Select Continue.
Below is the output when I entered the above commands. Windows 10 (1809) was installed in VirtualBox and was running in Audit mode.