More info:
I've found the current git for ipconfig (part of klibc) in http://git.kernel.org/cgit/libs/klibc/klibc.git/tree/usr/kinit/ipconfig/README.ipconfig?id=HEAD simply does not support the dns parameters that are specified.
It looks like initramfs-tools assumes it does, rather than pruning the dns entries (if supplied) and passing them to resolvconf.
More info:
I've found the current git for ipconfig (part of klibc) in git.kernel. org/cgit/ libs/klibc/ klibc.git/ tree/usr/ kinit/ipconfig/ README. ipconfig? id=HEAD
http://
simply does not support the dns parameters that are specified.
It looks like initramfs-tools assumes it does, rather than pruning the dns entries (if supplied) and passing them to resolvconf.