-debconf-set-selections <<< "iptables-persistent iptables-persistent/autosave_v4 boolean false"
-debconf-set-selections <<< "iptables-persistent iptables-persistent/autosave_v6 boolean false"
+echo 'iptables-persistent iptables-persistent/autosave_v4 boolean false' | debconf-set-selections
+echo 'iptables-persistent iptables-persistent/autosave_v6 boolean false' | debconf-set-selections