From c8745addbcba816e8327d17dac610f249c15c372 Mon Sep 17 00:00:00 2001
From: Padreug <padreug@aiolabs.dev>
Date: Thu, 2 Jul 2026 14:49:27 +0200
Subject: [PATCH] fix(deploy): make disk-image-sintra-usb BIOS+UEFI bootable
 (GRUB)
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The USB disk image was systemd-boot (UEFI-only) with make-disk-image's "efi"
table (pure GPT + ESP, protective MBR). The Sintra's Aaeon UP Board firmware
USB-boots in Legacy/BIOS mode — it boots the live ISO via that ISO's isolinux
(BIOS) El Torito image, not the UEFI ESP — so a dd'd systemd-boot image has no
BIOS boot code to execute and the firmware won't list it (a hand-added hybrid
MBR didn't help: nothing to run).

Switch the USB target to GRUB with BIOS + UEFI on make-disk-image's "hybrid"
table: it adds a bios_grub partition, GRUB writes its BIOS stage to the MBR AND
a removable /EFI/BOOT/BOOTX64.EFI — mirroring the live ISO's dual boot. The
Aaeon now lists it (as two "ia android" entries, BIOS + UEFI) and boots it.
Scoped to disk-image-sintra-usb only; the eMMC install keeps systemd-boot.
ESP stays partition 1 so the ESP-USB relabel step is unchanged.

Verified on hardware: booted from USB into the wizard with the full upboard.nix
hardware config.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
---
 flake.nix | 22 +++++++++++++++++++++-
 1 file changed, 21 insertions(+), 1 deletion(-)

diff --git a/flake.nix b/flake.nix
index a09ffdd..3a678da 100644
--- a/flake.nix
+++ b/flake.nix
@@ -342,6 +342,25 @@
                   fileSystems."/".device = lib.mkForce "/dev/disk/by-label/nixos-usb";
                   fileSystems."/boot".device = lib.mkForce "/dev/disk/by-label/ESP-USB";
                   system.autoUpgrade.enable = lib.mkForce false;
+
+                  # The Sintra's Aaeon firmware USB-boots in Legacy/BIOS mode — it
+                  # boots the live ISO via its isolinux (BIOS) El Torito image, not
+                  # the UEFI ESP. systemd-boot is UEFI-only, so a dd'd systemd-boot
+                  # image isn't recognised as bootable. Switch THIS USB image to
+                  # GRUB with BOTH BIOS (MBR + bios_grub partition, via the "hybrid"
+                  # table below) and UEFI (removable /EFI/BOOT/BOOTX64.EFI) — mirroring
+                  # the live ISO's dual boot — so it boots on Legacy and UEFI alike.
+                  # Scoped to the USB image; the eMMC install keeps systemd-boot.
+                  boot.loader.systemd-boot.enable = lib.mkForce false;
+                  boot.loader.efi.canTouchEfiVariables = lib.mkForce false;
+                  boot.loader.grub = {
+                    enable = lib.mkForce true;
+                    efiSupport = true;
+                    efiInstallAsRemovable = true;
+                    # make-disk-image's build VM exposes the image as /dev/vda;
+                    # GRUB installs its BIOS stage to that disk's MBR.
+                    devices = lib.mkForce [ "/dev/vda" ];
+                  };
                 })
               ];
             };
@@ -349,7 +368,8 @@
               inherit pkgs lib;
               config = cfg.config;
               format = "raw";
-              partitionTableType = "efi";
+              # hybrid = GPT + bios_grub partition + ESP → BIOS + UEFI bootable.
+              partitionTableType = "hybrid";
               diskSize = "auto";
               label = "nixos-usb"; # ext4 root label (make-disk-image -L)
             };