Tom Laramee wrote:

Greetings:

i have a pretty stock CentOS 5 machine with ports 80 and 22 exposed, so my /etc/sysconfig/iptables file is pretty standard/straightforward.

my question is: how is this config file initially generated? i'd like to re-create it, and add a couple of rules .... so i don't want to lose what's in there already.

i see that my /etc/sysconfig/system-config-securitylevel has three entries, which explains how the port 80 and 22 rules get into the config:

--enabled
--port=22:tcp
--port=80:tcp

... and i see the basic /etc/sysconfig/iptables-config file, but i'm unclear as to how the rest of the stuff gets in there: e.g.:

# Firewall configuration written by system-config-securitylevel
# Manual customization of this file is not recommended.
*filter
:INPUT ACCEPT [0:0]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [0:0]
:RH-Firewall-1-INPUT - [0:0]
-A INPUT -j RH-Firewall-1-INPUT
-A FORWARD -j RH-Firewall-1-INPUT
-A RH-Firewall-1-INPUT -i lo -j ACCEPT
-A RH-Firewall-1-INPUT -p icmp --icmp-type any -j ACCEPT
-A RH-Firewall-1-INPUT -p 50 -j ACCEPT
-A RH-Firewall-1-INPUT -p 51 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp --dport 5353 -d 224.0.0.251 -j ACCEPT
-A RH-Firewall-1-INPUT -p udp -m udp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -p tcp -m tcp --dport 631 -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state ESTABLISHED,RELATED -j ACCEPT
-A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 

22 -j ACCEPT -A RH-Firewall-1-INPUT -m state --state NEW -m tcp -p tcp --dport 80 -j ACCEPT -A RH-Firewall-1-INPUT -j REJECT --reject-with icmp-host-prohibited COMMIT

if you only want to add few simple rules, and if you know about iptables syntax, you can do something like # iptables-save > iptables.tmp edit the resulting files to adjust to your needs, then load it: # iptables-restore < iptables.tmp once you're happy, _backup_ /etc/sysconfig/iptables and do # iptables-save > /etc/sysconfig/iptables

Alternatively, use one of the available scripts or tools to create your configuration.

In any case, be aware that a misconfiguration could result in blocking your own access. so better test on a machine not far from you.