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# Create an initramfs containing the closure of the specified
# file system objects. An initramfs is used during the initial
# stages of booting a Linux system. It is loaded by the boot loader
# along with the kernel image. It's supposed to contain everything
# (such as kernel modules) necessary to allow us to mount the root
# file system. Once the root file system is mounted, the `real' boot
# script can be called.
#
# An initramfs is a cpio archive, and may be compressed with a number
# of algorithms.
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 u-boot
# compression type and filename extension.
compressorName = fullCommand: builtins.elemAt (builtins.match "([^ ]*/)?([^ ]+).*" fullCommand) 1;
in
{
stdenvNoCC,
cpio,
ubootTools,
lib,
pkgsBuildHost,
# 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 { object = path_or_derivation; symlink = "/path"; }
# The paths are copied into the initramfs in their nix store path
# form, then linked at the root according to `symlink`.
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 ? [ ],
# Whether to wrap the initramfs in a u-boot image.
makeUInitrd ? stdenvNoCC.hostPlatform.linux-kernel.target or "dummy" == "uImage",
# If generating a u-boot image, the architecture to use. The default
# guess may not align with u-boot's nomenclature correctly, so it can
# be overridden.
# See https://gitlab.denx.de/u-boot/u-boot/-/blob/9bfb567e5f1bfe7de8eb41f8c6d00f49d2b9a426/common/image.c#L81-106 for a list.
uInitrdArch ? stdenvNoCC.hostPlatform.linuxArch,
# The name of the compression, as recognised by u-boot.
# See https://gitlab.denx.de/u-boot/u-boot/-/blob/9bfb567e5f1bfe7de8eb41f8c6d00f49d2b9a426/common/image.c#L195-204 for a list.
# If this isn't guessed, you may want to complete the metadata above and send a PR :)
uInitrdCompression ?
_compressorMeta.ubootName
or (throw "Unrecognised compressor ${_compressorName}, please specify uInitrdCompression"),
}:
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
makeUInitrd
uInitrdArch
prepend
;
${if makeUInitrd then "uInitrdCompression" else null} = uInitrdCompression;
builder = ./make-initrd.sh;
nativeBuildInputs = [
cpio
]
++ lib.optional makeUInitrd ubootTools;
compress = "${_compressorExecutable} ${lib.escapeShellArgs _compressorArgsReal}";
# !!! should use XML.
objects = map (x: x.object) contents;
symlinks = map (x: x.symlink) contents;
suffices = map (x: if x ? suffix then x.suffix else "none") contents;
closureInfo = "${pkgsBuildHost.closureInfo { rootPaths = finalAttrs.objects; }}";
# Pass the function through, for reuse in append-initrd-secrets. The
# function is used instead of the string, in order to support
# cross-compilation (append-initrd-secrets running on a different
# architecture than what the main initramfs is built on).
passthru = {
compressorExecutableFunction = _compressorFunction;
compressorArgs = _compressorArgsReal;
};
})
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