26

I use amazon EC2 instance which works via ubuntu. By default according security restrictions I can't bin my application to port 80, so I just bind it port 8080 and then set routing redirect from port 80 to 8080 via the following command:

iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to 8080

But I found that when I reboot the server this settings no longer active untill I invoke this command again.

So my question is how to enable port's redirect work even if system was rebooted?

Ph0en1x
  • 405

4 Answers4

20

You can add this command in /etc/rc.local , so it will be executed automatically after reboot .

nux
  • 39,152
16

Use the iptables-save command instead.

Firewall rules should never go into rc.local script. rc.local is the last thing to be executed. If a block rule has been placed into rc.local there is a small time frame where an attacker can exploit a rule not being in place.

While it probably doesn't matter with this situation, it is still best to not get into a bad habit that may bite you later.

Zanna
  • 72,312
MeOMy
  • 161
6

Here is how the official iptables' documentation teaches us. See here

Add these two lines in /etc/network/interfaces:

pre-up iptables-restore < /etc/iptables.rules
post-down iptables-save > /etc/iptables.rules

The line post-down iptables-save > /etc/iptables.rules will save the rules to be used on the next boot.

Zanna
  • 72,312
Stavarengo
  • 161
  • 1
  • 2
0

I discovered a set of directories on Ubuntu 16.04 in /etc/network that will run scripts at various times during network initialization and shutdown:

if-down.d
if-post-down.d  
if-pre-up.d  
if-up.d
interfaces.d

So I found that I could dump the configuration as usual:

$ sudo sh -c "iptables-save > /etc/iptables.rules"

Then I created a file `/etc/network/if-pre-up.d/restore:

#!/bin/sh

iptables-restore < /etc/iptables.rules

... and flagged it executable

$ sudo chmod 755 /etc/network/if-pre-up.d/restore
mikebridge
  • 161