I have been using ubuntu for a long time. Nowadays, I wanted explore lubuntu. However, I cannot configure ufw. Actually I can but it does not respond. Basically, I cannot get the result of "ufw default deny" and others. I also can see chainrules of ufw with "iptables -L -n -v" ; however, nothing changes. Is there a problem commonly known about that? Or can you benefit from such configuration of ufw?