openwrt/package/base-files/files/bin/login.sh

#!/bin/sh
# Copyright (C) 2006-2011 OpenWrt.org

if ( ! grep -qs '^root::' /etc/shadow || \
     ! grep -qs '^root:[!x]\?:' /etc/passwd ) && \
   [ -z "$FAILSAFE" ]
then
	echo "Login failed."
	exit 0
else
cat << EOF
 === IMPORTANT ============================
  Use 'passwd' to set your login password
  this will disable telnet and enable SSH
 ------------------------------------------
EOF
fi

exec /bin/ash --login