nixpkgs/pkgs/build-support/kernel/make-initrd.sh
Thomas Watson 7fd6cea253 make-initrd: fix reproducibility problems
cpio includes the number of directory hard links in archives it creates.
Some filesystems, like btrfs, do not count directory hard links the same
way as more common filesystems like ext4 or tmpfs, so archives built
when /tmp is on such a filesystem do not reproduce. This patch replaces
cpio with bsdtar, which does not have this issue. The specific
invocation is from this page:
https://reproducible-builds.org/docs/archives/
2022-04-14 19:06:30 -05:00

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source $stdenv/setup
set -o pipefail
objects=($objects)
symlinks=($symlinks)
suffices=($suffices)
mkdir root
# Needed for splash_helper, which gets run before init.
mkdir root/dev
mkdir root/sys
mkdir root/proc
for ((n = 0; n < ${#objects[*]}; n++)); do
object=${objects[$n]}
symlink=${symlinks[$n]}
suffix=${suffices[$n]}
if test "$suffix" = none; then suffix=; fi
mkdir -p $(dirname root/$symlink)
ln -s $object$suffix root/$symlink
done
# Get the paths in the closure of `object'.
storePaths=$(perl $pathsFromGraph closure-*)
# Paths in cpio archives *must* be relative, otherwise the kernel
# won't unpack 'em.
(cd root && cp -prP --parents $storePaths .)
# Put the closure in a gzipped cpio archive.
mkdir -p $out
for PREP in $prepend; do
cat $PREP >> $out/initrd
done
(cd root && find * .[^.*] -exec touch -h -d '@1' '{}' +)
(cd root && find * .[^.*] -print0 | sort -z | bsdtar --uid 0 --gid 0 -cnf - -T - | bsdtar --null -cf - --format=newc @- | eval -- $compress >> "$out/initrd")
if [ -n "$makeUInitrd" ]; then
mkimage -A "$uInitrdArch" -O linux -T ramdisk -C "$uInitrdCompression" -d "$out/initrd" $out/initrd.img
# Compatibility symlink
ln -sf "initrd.img" "$out/initrd"
else
ln -s "initrd" "$out/initrd$extension"
fi