I was reading this tutorial and this (Option Two from there) and as far as I understand, making a Windows USB drive bootable for UEFI requires:

  • rewriting the partition table and formatting as FAT32
  • copying Windows files on USB drive
  • copying an extra file (bootx64.efi) if it doesn't exist

There is no bootloader installation procedure, like you would do with a BIOS bootable USB using the bootsect utility from Windows installation media in the boot folder:

bootsect.exe /nt60 F:

My question is, can a USB drive with no MBR boot in UEFI mode?

  • 1
    UEFI expects GPT partitions not MBR partitions – Ramhound Oct 10 '14 at 10:06
up vote 2 down vote accepted

Yes. It’s also not about GPT or MBR partitioning schemes. It just needs to be FAT32 (could work with other filesystems too, depending on what the actual UEFI implementation supports) and have the bootx64.efi file at the right location.

Yes, an USB drive with no MBR can boot in UEFI mode:

In addition to the standard PC disk partition scheme, which uses a master boot record (MBR), UEFI works with a new partitioning scheme: GUID Partition Table (GPT). GPT is free from many of the limitations of MBR.

The UEFI spec requires support for GPT disks. Having said that, many machines will happily boot in UEFI mode from a USB stick partitioned either MBR or GPT, but NOT ALL WILL. I had a Lenovo laptop I was working on and it refused to see a UEFI boot source on my USB until I converted it from MBR partition scheme to GPT. Hope that helps

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