How to verify if iptables is running or the firewall is activated

When I run on my linux Redhat version 6.8 machine - service iptables status

I get the rules table ( but not if iptables running or not )

Does the following show that iptables is running?

 # service iptables status Table: filter Chain INPUT (policy ACCEPT) num target prot opt source destination 1 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 state RELATED,ESTABLISHED 2 ACCEPT icmp -- 0.0.0.0/0 0.0.0.0/0 3 ACCEPT all -- 0.0.0.0/0 0.0.0.0/0 4 ACCEPT tcp -- 0.0.0.0/0 0.0.0.0/0 state NEW tcp dpt:22 5 REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject- with icmp-host-prohibited Chain FORWARD (policy ACCEPT) num target prot opt source destination 1 REJECT all -- 0.0.0.0/0 0.0.0.0/0 reject- with icmp-host-prohibited
Chain OUTPUT (policy ACCEPT)
num target prot opt source destination

Iptables is enabled on boot

# chkconfig --list iptables
iptables 0:off 1:off 2:on 3:on 4:on 5:on 6:off

3 Answers

There is no such thing as "iptables is running" - there is no dedicated firewall process to monitor.

If the kernel modules are loaded and rules defined (both of which are proven by showing a valid rules table), the filtering is active. It is done in-kernel on events (packet rcv/snd) and not on a separate process.

So: Yes, if the rules shown are what you want, then your firewall is up.

This way we can know only if its not running

[root@vm1 ~]# service iptables status iptables: Firewall is not running.

if running , it prints rules table as shown to you

On Ubuntu 20.04, I used service iptables status to show the following:

~$ service iptables status
● iptables.service - netfilter persistent configuration Loaded: loaded (/etc/alternatives/iptables.service; enabled; vendor preset: enabled) Active: inactive (dead) Docs: man:netfilter-persistent(8)
~$ service iptables restart
==== AUTHENTICATING FOR org.freedesktop.systemd1.manage-units ===
Authentication is required to restart 'iptables.service'.
Authenticating as: <user id>
Password:
==== AUTHENTICATION COMPLETE ===
~$ service iptables status
● iptables.service - netfilter persistent configuration Loaded: loaded (/etc/alternatives/iptables.service; enabled; vendor preset: enabled) Active: active (exited) since Sun 2021-01-31 08:25:23 EST; 11s ago Docs: man:netfilter-persistent(8) Process: 140486 ExecStart=/usr/sbin/netfilter-persistent start (code=exited, status=0/SUCCESS) Main PID: 140486 (code=exited, status=0/SUCCESS)