firewall-ufw†
serverworld blog: https://www.server-world.info/query?os=Ubuntu_22.04&p=ufw&f=1
sudo ufw status #Status: inactive
sudo ufw enable
sudo ufw status #Status: active
sudo ufw status verbose #Default: deny (incoming), allow (outgoing), disabled (routed)
sudo ufw allow ssh
sudo ufw status verbose
sudo ufw delete allow ssh
sudo ufw status verbose
sudo ufw reload
sudo ufw delete allow 8080/tcp
sudo ufw app list
sudo vim /etc/ufw/before.rules #ICMP関連すべてコメントアウト
#家だけ許可する場合:-A ufw-before-input -p icmp --icmp-type echo-request -s 192.168.1.0/24 -j ACCEPT
占用されたとき†
sudo netstat -tuln | grep 8080
sudo kill <PID>