@chevengur I can tell you how I would go about figuring this this.
Take a computer that represents the finished design of how your disk are laid out. Schedule a deployment to that computer, but before you hit the schedule task button, tick the debug checkbox then schedule the deployment. No worries as long as you pick debug mode since it will never get to the deployment phase. Now pxe boot the target computer, it should boot into the FOS linux console. After a few screens of text you need to clear with the enter key you will be dropped to the FOS linux command prompt. From there issue, the efibootmgr command with no parameters. It should print something similar to below (note this is from my laptop) thunder@lightning:~$ efibootmgr BootCurrent: 0005 Timeout: 2 seconds BootOrder: 0005,0004,0000,0001,0002,0003 Boot0000* UEFI BC511 NVMe SK hynix 256GB SN9BN62231050BJ2H 1 HD(1,GPT,d00df89f-1edb-44f8-b325-245b607b2321,0x800,0x100000)/File(\EFI\Boot\BootX64.efi){auto_created_boot_option} Boot0001* ONBOARD NIC (IPV4) PciRoot(0x0)/Pci(0x1f,0x6)/MAC(b44,0)/IPv4(0.0.0.00.0.0.0,0,0){auto_created_boot_option} Boot0002* ONBOARD NIC (IPV6) PciRoot(0x0)/Pci(0x1f,0x6)/MAC(b440)/IPv6([::]:<->[::]:,0,0){auto_created_boot_option} Boot0003* UEFI HTTPs Boot (MAC:B445065BDC4B) PciRoot(0x0)/Pci(0x1f,0x6)/MAC(b445065bdc4b,0)/IPv4(0.0.0.00.0.0.0,0,0)/Uri(){auto_created_boot_option} Boot0004* debian HD(1,GPT,d00df89f-1edb-07b2321,0x800,0x100000)/File(\EFI\debian\shimx64.efi) Boot0005* Ubuntu HD(1,GPT,d00df89f-1edb-607b2321,0x800,0x100000)/File(\EFI\ubuntu\shimx64.efi)You can see from this the default BootOrder is 5, 4, 0, 1, 2, 3 this lists the different boot managers found by the firmware.
So it will boot ubuntu first, then debian, the hard drive, onboard nic v4, onboard nic v6, http boot.
Now lets say I wanted debian to boot first I might issue the command.
efibootmgr -o 4,5, 0,1, 2, 3
Now reboot the computer with the reboot command see if it changes the boot order specific to your options.
After you get this worked out, you will need to clean up this deploy task on your fog server so it doesn’t do this moving forward. But for debugging as long as the fos engine doesn’t complete, every time you reboot the computer will enter the FOS debug console. This helps with debugging and tweaking your post install script.