Busybox's cpio doesn't list all hardlinks (if there's more than 1) in the archive.

Example:
###########################
echo "ZZZZZ" > a
ln a b # b is a hardlink to a
ls | cpio -ov -H newc > /tmp/new.cpio # Creates a new archive with a and b

# Debian's cpio, lists both a and b
cpio -t < /tmp/new.cpio

# Busybox's cpio, lists only a
./busybox cpio -t < /tmp/new.cpio
###########################


I've compiled busybox with the default config.