How to Start/Stop and Enable/Disable FirewallD Service

If you’re using CentOS/RHEL 7 or Fedora 18+ versions, you should follow below instructions to manage FirewallD service.
Start FirewallD Service
# systemctl start firewalld 
Stop FirewallD Service
# systemctl stop firewalld
Check the Status of FirewallD
# systemctl status firewalld
Check the State of FirewallD
# firewall-cmd --state
As an alternative, you can disable the firewalld service so that it doesn’t apply rules to packets and enable ones needed again.
Disable FirewallD Service
# systemctl disable firewalld
Enable FirewallD Service
# systemctl enable firewalld
Mask FirewallD Service
# systemctl mask firewalld
Also, you can mask the firewall service which creates a symbolic link of the firewall.service to /dev/null, thus disabling the service.
Unmask FirewallD Service
# systemctl unmask firewalld
This is reverse of masking the service. This removes the symlink of the service created during masking, thus re-enabling the service.

How to Start/Stop and Enable/Disable IPtables Service

On RHEL/CentOS 6/5/4 and Fedora 12-18 iptables firewall comes as pre and later, the iptables service can be installed via:
# yum install iptables-services
Then, the service can be started, stopped or restarted via following commands:
Start Iptables Service
# systemctl start iptables
# service iptables start
Stop Iptables Service
# systemctl stop iptables
# service iptables stop
Disable Iptables Service
# systemctl disable iptables
# service iptables save
# service iptables stop
Enable Iptables Service
# systemctl enable iptables
# service iptables start
Check Status of Iptables Service
# systemctl status iptables
# service iptables status
On Ubuntu and some other Linux distributions however, ufw is the command which is used to manage the iptables firewall service. Ufw provides an easy interface for the user to handle the iptables firewall service.
Enable Ufw Iptables Firewall
$ sudo ufw enable
Disable Ufw Iptables Firewall
$ sudo ufw disable
Check Status of Ufw Iptables Firewall
# sudo ufw status 
However, if you want to list chains in iptables which contains all the rules following command can help you achieve the same:
# iptables -L -n -v

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