New
#11
Here's the rundown on creating a system partition to boot from. You can use whatever partitioning program you desire to meet the following requirements:
1. You need at least 100mb unallocated on the drive to create the system partition in. If you are going to boot in legacy bios/CSM mode, the drive must be MBR partitioned. If you are going to boot in UEFI mode, the drive can be either MBR or GPT partitioned.
2. You need to create a primary partition in the unallocated space.
If your drive is MBR partitioned, the diskpart command is:
create part pri size=100.
If your drive is GPT partitioned, the command is:
create part EFI size=100. Size=100 sets the size of the partition at 100mb. Set it lower than 100mb and you risk an upgrade of one version of Windows to the next version of Windows failing (IE: 1803 to 1809). Rarely is more than 100mb needed. You can change the size if you want, or leave the size off the command to use all the remaining contiguous free space on the drive. An EFI partition cannot be created on an MBR drive, it has to be a PRImary partition. UEFI booting does not required an EFI system partition type to boot from, it only requires a FAT32 partition to boot from, and it cannot be a logical partition.
3. If you are going to boot in legacy BIOS/CSM mode, the partition must be active. The diskpart command is simply:
active. The partition can only be marked as active on an MBR partitioned drive. If you are going to boot in UEFI mode and the drive is MBR partitioned, I suggest you set it as active anyway, but not required.
4. Format the partition as FAT32. Diskpart command is:
format fs=fat32 quick.
5. Assign the partition a temporary drive letter. Diskpart comand is:
assign letter=W. You can use any unused drive letter.
6. Exit diskpart with the command:
exit
7. Back at the command prompt, the command to make the partition bootable is:
bcdboot C:\Windows /s W: /f ALL. In the command prompt environment, your Windows may not be C: drive. Change C:\ to whatever driver your Windows actually is. Change W: to whatever drive letter you assigned to your new system partition. /f ALL means the partition is bootable in all modes: legacy BIOS, CSM, UEFI, assuming all other requirements are met.
So...that proves my point that GPT is not required to boot in UEFI mode. If it was, the /f ALL switch could not work, because the drive must be MBR partitioned to boot in legacy BIOS/CSM mode. The /f ALL switch can only work if the drive is MBR partitioned AND the system partition is formatted as FAT32,