# This module creates a bootable SD card image containing the given NixOS # configuration. The generated image is MBR partitioned, with a FAT # /boot/firmware partition, and ext4 root partition. The generated image # is sized to fit its contents, and a boot script automatically resizes # the root partition to fit the device on the first boot. # # The firmware partition is built with expectation to hold the Raspberry # Pi firmware and bootloader, and be removed and replaced with a firmware # build for the target SoC for other board families. # # The derivation for the SD image will be placed in # config.system.build.sdImage { config, lib, pkgs, ... }: with lib; let rootfsImage = pkgs.callPackage ../../../lib/make-ext4-fs.nix ({ inherit (config.sdImage) storePaths; compressImage = config.sdImage.compressImage; populateImageCommands = config.sdImage.populateRootCommands; volumeLabel = "NIXOS_SD"; } // optionalAttrs (config.sdImage.rootPartitionUUID != null) { uuid = config.sdImage.rootPartitionUUID; }); in { imports = [ (mkRemovedOptionModule [ "sdImage" "bootPartitionID" ] "The FAT partition for SD image now only holds the Raspberry Pi firmware files. Use firmwarePartitionID to configure that partition's ID.") (mkRemovedOptionModule [ "sdImage" "bootSize" ] "The boot files for SD image have been moved to the main ext4 partition. The FAT partition now only holds the Raspberry Pi firmware files. Changing its size may not be required.") ../../profiles/all-hardware.nix ]; options.sdImage = { imageName = mkOption { default = "${config.sdImage.imageBaseName}-${config.system.nixos.label}-${pkgs.stdenv.hostPlatform.system}.img"; description = '' Name of the generated image file. ''; }; imageBaseName = mkOption { default = "nixos-sd-image"; description = '' Prefix of the name of the generated image file. ''; }; storePaths = mkOption { type = with types; listOf package; example = literalExpression "[ pkgs.stdenv ]"; description = '' Derivations to be included in the Nix store in the generated SD image. ''; }; firmwarePartitionOffset = mkOption { type = types.int; default = 8; description = '' Gap in front of the /boot/firmware partition, in mebibytes (1024×1024 bytes). Can be increased to make more space for boards requiring to dd u-boot SPL before actual partitions. Unless you are building your own images pre-configured with an installed U-Boot, you can instead opt to delete the existing `FIRMWARE` partition, which is used **only** for the Raspberry Pi family of hardware. ''; }; firmwarePartitionID = mkOption { type = types.str; default = "0x2178694e"; description = '' Volume ID for the /boot/firmware partition on the SD card. This value must be a 32-bit hexadecimal number. ''; }; firmwarePartitionName = mkOption { type = types.str; default = "FIRMWARE"; description = '' Name of the filesystem which holds the boot firmware. ''; }; rootPartitionUUID = mkOption { type = types.nullOr types.str; default = null; example = "14e19a7b-0ae0-484d-9d54-43bd6fdc20c7"; description = '' UUID for the filesystem on the main NixOS partition on the SD card. ''; }; firmwareSize = mkOption { type = types.int; # As of 2019-08-18 the Raspberry pi firmware + u-boot takes ~18MiB default = 30; description = '' Size of the /boot/firmware partition, in megabytes. ''; }; populateFirmwareCommands = mkOption { example = literalExpression "'' cp \${pkgs.myBootLoader}/u-boot.bin firmware/ ''"; description = '' Shell commands to populate the ./firmware directory. All files in that directory are copied to the /boot/firmware partition on the SD image. ''; }; populateRootCommands = mkOption { example = literalExpression "''\${config.boot.loader.generic-extlinux-compatible.populateCmd} -c \${config.system.build.toplevel} -d ./files/boot''"; description = '' Shell commands to populate the ./files directory. All files in that directory are copied to the root (/) partition on the SD image. Use this to populate the ./files/boot (/boot) directory. ''; }; postBuildCommands = mkOption { example = literalExpression "'' dd if=\${pkgs.myBootLoader}/SPL of=$img bs=1024 seek=1 conv=notrunc ''"; default = ""; description = '' Shell commands to run after the image is built. Can be used for boards requiring to dd u-boot SPL before actual partitions. ''; }; compressImage = mkOption { type = types.bool; default = true; description = '' Whether the SD image should be compressed using zstd. ''; }; expandOnBoot = mkOption { type = types.bool; default = true; description = '' Whether to configure the sd image to expand it's partition on boot. ''; }; }; config = { fileSystems = { "/boot/firmware" = { device = "/dev/disk/by-label/${config.sdImage.firmwarePartitionName}"; fsType = "vfat"; # Alternatively, this could be removed from the configuration. # The filesystem is not needed at runtime, it could be treated # as an opaque blob instead of a discrete FAT32 filesystem. options = [ "nofail" "noauto" ]; }; "/" = { device = "/dev/disk/by-label/NIXOS_SD"; fsType = "ext4"; }; }; sdImage.storePaths = [ config.system.build.toplevel ]; system.build.sdImage = pkgs.callPackage ({ stdenv, dosfstools, e2fsprogs, mtools, libfaketime, util-linux, zstd }: stdenv.mkDerivation { name = config.sdImage.imageName; nativeBuildInputs = [ dosfstools e2fsprogs libfaketime mtools util-linux ] ++ lib.optional config.sdImage.compressImage zstd; inherit (config.sdImage) imageName compressImage; buildCommand = '' mkdir -p $out/nix-support $out/sd-image export img=$out/sd-image/${config.sdImage.imageName} echo "${pkgs.stdenv.buildPlatform.system}" > $out/nix-support/system if test -n "$compressImage"; then echo "file sd-image $img.zst" >> $out/nix-support/hydra-build-products else echo "file sd-image $img" >> $out/nix-support/hydra-build-products fi root_fs=${rootfsImage} ${lib.optionalString config.sdImage.compressImage '' root_fs=./root-fs.img echo "Decompressing rootfs image" zstd -d --no-progress "${rootfsImage}" -o $root_fs ''} # Gap in front of the first partition, in MiB gap=${toString config.sdImage.firmwarePartitionOffset} # Create the image file sized to fit /boot/firmware and /, plus slack for the gap. rootSizeBlocks=$(du -B 512 --apparent-size $root_fs | awk '{ print $1 }') firmwareSizeBlocks=$((${toString config.sdImage.firmwareSize} * 1024 * 1024 / 512)) imageSize=$((rootSizeBlocks * 512 + firmwareSizeBlocks * 512 + gap * 1024 * 1024)) truncate -s $imageSize $img # type=b is 'W95 FAT32', type=83 is 'Linux'. # The "bootable" partition is where u-boot will look file for the bootloader # information (dtbs, extlinux.conf file). sfdisk $img <