This is an old revision of the document! Debian firewalld apt-get install firewalld firewall-cmd --permanent --zone=public --change-interface=eth0 firewall-cmd --permanent --add-port=10001/tcp --permanent firewall-cmd --reload References https://ec.europa.eu/digital-building-blocks/sites/display/CEKB/How+to+open+a+port+on+the+firewall https://serverfault.com/questions/748946/firewalld-not-listing-any-active-zones