I have this rule in my iptables:

iptables -A INPUT -s -j LOG

My question is:

Where is the iptables log file, and how can I change that?


These logs are generated by the kernel, so they go to the file that receives kernel logs: /var/log/kern.log.

If you want to redirect these logs to a different file, that can't be done through iptables. It can be done in the configuration of the program that dispatches logs: rsyslog. In the iptables rule, add a prefix that isn't used by any other kernel log:

iptables -A INPUT -s -j LOG --log-prefix='[netfilter] '

Following the example set by 20-ufw.conf, create a file under /etc/rsyslog.d/my_iptables.conf containing

:msg,contains,"[netfilter] " /var/log/iptables.log
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  • i dont have installed ufw, so i cannot find logs in syslog,kern.log or iptables.log – pylover Sep 21 '13 at 19:47
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    @pylover UFW was just an example. I know you don't have iptables.log, the point of my answer is to show you how to create it. You may not have /var/log/kern.log if you're running a different version of Ubuntu (I think recent versions no longer use this file and put kernel logs in /var/log/syslog instead), but it doesn't matter. Oh, but if you're running an older version of Ubuntu, you may need to install the rsyslog package. – Gilles 'SO- stop being evil' Sep 21 '13 at 19:50
  • To make this work on 12.10, I had to adjust the rsyslog.d file to have the following additional char: ":msg,contains,"[netfilter] " -/var/log/iptables.log" – Daniel Feb 26 '14 at 15:10
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    one more thing, i needed to name the file like 00-my_iptables.conf, otherwise iptables still were logging into kern.log – Valentin Kantor Jan 3 '15 at 12:02
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    Maybe you could mentioned the & stop command as well. That way you avoid duplicates in the kern.log file, duplicates that could imper your ability to see other important kernel logs. – Alexis Wilke Oct 21 '16 at 20:08

I know that's far too late and the answer is already marked as the accepted one. I just have a piece of new info to give.

The log file of the LOG action is found at either /var/log/syslog (Ubuntu and similar OSs) or /var/log/messages (CentOS and similar OSs).

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If you are in trouble finding the right file you may try like this:

find /var/log -mmin 1

This will find any file modified in the last 1 min inside the /var/log and below. You may find out that the -j LOG may update more than just a single file.

For instance on Ubuntu 18, both the /var/log/kern.log and /var/log/syslog are impacted with netfilter logging.

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