let
  # Some metadata on various compression programs, relevant to naming
  # the initramfs file and, if applicable, generating a u-boot image
  # from it.
  compressors = import ./initrd-compressor-meta.nix;
  # Get the basename of the actual compression program from the whole
  # compression command, for the purpose of guessing the
  # compression type and filename extension.
  compressorName = fullCommand: builtins.elemAt (builtins.match "([^ ]*/)?([^ ]+).*" fullCommand) 1;
in
{
  stdenvNoCC,
  cpio,
  lib,
  pkgsBuildHost,
  makeInitrdNGTool,
  binutils,
  # Name of the derivation (not of the resulting file!)
  name ? "initrd",

  # Program used to compress the cpio archive; use "cat" for no compression.
  # This can also be a function which takes a package set and returns the path to the compressor,
  # such as `pkgs: "${pkgs.lzop}/bin/lzop"`.
  compressor ? "gzip",
  _compressorFunction ?
    if lib.isFunction compressor then
      compressor
    else if !builtins.hasContext compressor && builtins.hasAttr compressor compressors then
      compressors.${compressor}.executable
    else
      _: compressor,
  _compressorExecutable ? _compressorFunction pkgsBuildHost,
  _compressorName ? compressorName _compressorExecutable,
  _compressorMeta ? compressors.${_compressorName} or { },

  # List of arguments to pass to the compressor program, or null to use its defaults
  compressorArgs ? null,
  _compressorArgsReal ?
    if compressorArgs == null then _compressorMeta.defaultArgs or [ ] else compressorArgs,

  # Filename extension to use for the compressed initramfs. This is
  # included for clarity, but $out/initrd will always be a symlink to
  # the final image.
  # If this isn't guessed, you may want to complete the metadata above and send a PR :)
  extension ?
    _compressorMeta.extension
      or (throw "Unrecognised compressor ${_compressorName}, please specify filename extension"),

  # List of { source = path_or_derivation; target = "/path"; }
  # The paths are copied into the initramfs in their nix store path
  # form, then linked at the root according to `target`.
  contents,

  # List of uncompressed cpio files to prepend to the initramfs. This
  # can be used to add files in specified paths without them becoming
  # symlinks to store paths.
  prepend ? [ ],

  # Deprecated; remove in 27.05.
  makeUInitrd ? null,
  uInitrdArch ? null,
  uInitrdCompression ? null,
}:
assert lib.assertMsg (makeUInitrd == null && uInitrdArch == null && uInitrdCompression == null)
  "makeInitrdNg: U‐Boot legacy image support has been removed as it is deprecated upstream and ARMv5 kernels no longer default to uImage";
stdenvNoCC.mkDerivation (finalAttrs: {
  __structuredAttrs = true;

  # the initrd will be self-contained so we can drop references
  # to the closure that was used to build it
  unsafeDiscardReferences.out = true;

  inherit
    name
    extension
    prepend
    ;

  compress = "${_compressorExecutable} ${lib.escapeShellArgs _compressorArgsReal}";
  contentsJSON = builtins.toJSON contents;

  nativeBuildInputs = [
    makeInitrdNGTool
    cpio
  ];

  buildCommand = ''
    mkdir -p ./root/{run,tmp,var/empty}
    ln -s ../run ./root/var/run
    make-initrd-ng <(echo "$contentsJSON") ./root
    mkdir "$out"
    (cd root && find . -exec touch -h -d '@1' '{}' +)
    for PREP in ''${prepend[@]}; do
      cat $PREP >> $out/initrd
    done
    (cd root && find . -print0 | sort -z | cpio --quiet -o -H newc -R +0:+0 --reproducible --null | eval -- $compress >> "$out/initrd")

    ln -s "initrd" "$out/initrd$extension"
  '';

  passthru = {
    compressorExecutableFunction = _compressorFunction;
    compressorArgs = _compressorArgsReal;
  };
})