Linux - Firewall

$ su

Ubuntu

$ systemctl stop ufw
$ systemctl disable ufw

$ systemctl status ufw

$ systemctl enable ufw
$ systemctl start ufw

http://jasonmun.blogspot.my/2016/12/ubuntu-firewall.html

Fedora / CentOS

$ systemctl stop firewalld
$ systemctl disable firewalld

$ systemctl status firewalld

$ systemctl enable firewalld
$ systemctl start firewalld

$ firewall-cmd --get-active-zones

$ firewall-cmd --add-port={110/tcp,143/tcp} --permanent --zone=FedoraWorkstation
$ firewall-cmd --add-service=telnet --permanent --zone=FedoraWorkstation

$ firewall-cmd --reload
$ firewall-cmd --list-all --zone=FedoraWorkstation

OpenSUSE

$ systemctl stop SuSEfirewall2
$ systemctl disable SuSEfirewall2

$ systemctl status SuSEfirewall2

$ systemctl enable SuSEfirewall2
$ systemctl start SuSEfirewall2

http://jasonmun.blogspot.my/2017/01/opensuse-firewall.html