nixpkgs/boot/make-initrd.nix

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# Create an initial ramdisk containing the closure of the specified
# file system objects. An initial ramdisk 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 initrd is really just a gzipped cpio archive.
#
# Symlinks are created for each top-level file system object. E.g.,
# `contents = {object = ...; symlink = /init;}' is a typical
# argument.
{stdenv, perl, cpio, contents}:
stdenv.mkDerivation {
name = "initrd";
builder = ./make-initrd.sh;
buildInputs = [perl cpio];
# !!! 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;
# For obtaining the closure of `contents'.
exportReferencesGraph =
map (x: [("closure-" + baseNameOf x.symlink) x.object]) contents;
pathsFromGraph = ../helpers/paths-from-graph.pl;
}