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An Hybrid UEFI GPT + BIOS GPT/MBR boot USB disk is a disk that works on both UEFI and BIOS PCs.


A working Linux installation with the following packages: grub2, grub2-efi, gdisk (on Debian Jessie: grub-pc-bin, grub-efi, grub-efi-amd64, gdisk) An USB drive Some Linux ISO.

Step 1: get the proper /dev

From now on we will use a root shell because almost all commands we will use require it.

root@debianvm:~# fdisk -l


Disk /dev/sdc: 14.9 GiB, 16005464064 bytes, 31260672 sectors
Units: sectors of 1 * 512 = 512 bytes
Sector size (logical/physical): 512 bytes / 512 bytes
I/O size (minimum/optimal): 512 bytes / 512 bytes
Disklabel type: dos
Disk identifier: 0x00000000

Device     Boot Start      End  Sectors  Size Id Type
/dev/sdc1           2 31260671 31260670 14.9G af HFS / HFS+

Find the right dev (ie: mine was /dev/sdc and i will use it in the guide).

Step 2: make GUID partition

root@debianvm:~# gdisk /dev/sdc
And then we are in gdisk prompt; from now on just give the commands in bold and the press enter.

root@debianvm:~# gdisk /dev/sdc
GPT fdisk (gdisk) version 0.8.10

Partition table scan:

  • MBR: MBR only
    BSD: not present
    APM: not present
    GPT: not present

Found invalid GPT and valid MBR; converting MBR to GPT format
typing 'q' if you don't want to convert your MBR partitions
to GPT format!

Warning! Main partition table overlaps the first partition by 32 blocks!
You will need to delete this partition or resize it in another utility.

Warning! Secondary partition table overlaps the last partition by
33 blocks!
You will need to delete this partition or resize it in another utility.

Command (? for help): o
This option deletes all partitions and creates a new protective MBR.
Proceed? (Y/N): y