Unpacking and repacking an initrd (2023)

# tested on current Tumbleweed 20230901
cp /boot/initrd-6.4.12-1-default .
mkdir -p part1 part2
cpio -idv -D part1 < initrd-6.4.12-1-default
/usr/lib/dracut/skipcpio initrd-6.4.12-1-default | zstd -d | cpio -idv -D part2
# [optional: make changes to extracted files in part2]
(cd part1 && find . | cpio -ocv > ../part1.cpio)
(cd part2 && find . | cpio -ocv > ../part2.cpio)
cat part1.cpio part2.cpio > initrd.test
cp initrd.test /boot/initrd-6.4.12-1-default
reboot
# and it works...