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feat(deploy): add disk-image-sintra-usb with distinct partition labels

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A USB-bootable Sintra image variant for booting on a machine whose eMMC
already holds a nixos/ESP-labelled install. make-disk-image hardcodes the
root/ESP labels (nixos/ESP); booting the standard image from USB next to
the eMMC races stage-1's by-label/nixos between the two roots and likely
mounts the eMMC. This variant labels root nixos-usb (via make-disk-image
-L) and relabels the ESP to ESP-USB in a post-step (mtools), with
fileSystems pointed at the new labels. Auto-upgrade is disabled — it's a
portable test / hand-off image, and that also removes scheduled bootloader
writes that could land on the eMMC's ESP.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
This commit is contained in:
Padreug 2026-06-29 23:47:18 +02:00
commit ce649947f6
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flake.nix
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@ -326,6 +326,51 @@
diskSize = "auto";
};
# USB-bootable Sintra image with DISTINCT partition labels
# (nixos-usb / ESP-USB) so the stick can be booted on a Sintra whose
# eMMC already holds a nixos/ESP-labelled install without a by-label
# collision — stage-1 would otherwise race between the two roots and
# likely mount the eMMC. Auto-upgrade is disabled: this is a portable
# test / hand-off image, not a managed fleet member, and disabling it
# also removes the scheduled bootloader writes that could otherwise
# land on the eMMC's ESP.
disk-image-sintra-usb =
let
cfg = self.nixosConfigurations.sintra-installed.extendModules {
modules = [
({ lib, ... }: {
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;
})
];
};
baseImage = import (nixpkgs + "/nixos/lib/make-disk-image.nix") {
inherit pkgs lib;
config = cfg.config;
format = "raw";
partitionTableType = "efi";
diskSize = "auto";
label = "nixos-usb"; # ext4 root label (make-disk-image -L)
};
in
pkgs.runCommand "nixos-disk-image-sintra-usb"
{ nativeBuildInputs = [ pkgs.parted pkgs.mtools ]; }
''
mkdir -p $out
cp --sparse=always ${baseImage}/nixos.img $out/nixos.img
chmod +w $out/nixos.img
# make-disk-image hardcodes the ESP FAT label to "ESP"; relabel the
# volume to ESP-USB so /boot (by-label/ESP-USB) doesn't collide with
# the eMMC's ESP. Volume label only — bootloader files are untouched,
# and UEFI loads /EFI/BOOT/BOOTX64.EFI regardless of the label.
espStart=$(parted -sm "$out/nixos.img" unit B print | awk -F: '$1==1 {gsub("B","",$2); print $2}')
echo "ESP partition starts at byte $espStart — relabelling to ESP-USB"
export MTOOLS_SKIP_CHECK=1
mlabel -i "$out/nixos.img@@$espStart" ::ESP-USB
printf 'verify ESP label: '; mlabel -i "$out/nixos.img@@$espStart" -s :: || true
'';
# Backwards compat
iso = self.nixosConfigurations.douro.config.system.build.isoImage;
};