Need help creating universal multiboot 'fixed' USB

My goal is to create a single bootable 'fixed disk' usb drive that can boot my custom winpe and Parted Magic on UEFI (secure boot) or BIOS. I would also like to be able to create an iso though I'm sure it'll require some boot entry edits. I have ideas but it is taking me a long time to figure out all details.

My idea is to set up hybrid MBR with 2 partitions: ESP and exFAT. I'm hoping someone here has done this or similar. I'm comfortable using any cli tools including dd and gdisk and editing boot entries for grub2, syslinux, or grub4dos. I haven't learned yet how to (chainload?) from the exfat partition.

I am not fond of booting an iso file from grub or BCD. I am open to all suggestions otherwise.

To support Secure Boot, you would need either Windows bootmgfw.efi or grub2 (x64 only).

If you use bootmgfw.efi (as \EFI\BOOT\bootx64.efi) then I am not sure how you would UEFI-boot to Parted Magic from that?

 

So the alternative is to boot to grub2 and then from there boot to pmagic or WinPE.

 

If your WinPE wim file is less than 4GB, then only a single FAT32 partition is required.

 

Once you have secure booting working, getting MBR-booting to work should be easier.

 

You would need signed grub2 boot files for Secure Boot (eg. from a Ubuntu ISO).

My pe wim is less than 4gb but I need to store other big files. One way I'm struggling is that I was trying to make a proper hidden ESP which would boot the files on the exFAT volume. Maybe most UEFI only need a fat32 with EFI folder? I was trying to follow the guidelines on gpt fdisk hybrid mbr page but once I create the hybrid mbr, I can't seem to mount that partition in windows and it seems like I will have to dd the mbr bootloader stuff from linux. Maybe I'm over-thinking this?

EFI or GPT partitions are not required for UEFI-booting from a USB drive.

Just a simple primary FAT32 partition is all that is needed.

 

To perform a full UEFI installation of Windows, Setup.exe insists on GPT partitions, but for any other boot purpose, GPT is not needed (or even desired!).

http://www.easy2boot...things-to-know/

double posted thx to my phone

Edited by x79, 05 April 2017 - 06:12 PM.