Iptables is a firewall utility that allows you to control incoming and outgoing network traffic on a Linux system. If you want to flush (reset) the iptables rules on an Ubuntu Linux system, you can use the iptables command with the -F option.
To flush the iptables rules, run the following command:
sudo iptables -F
This will flush all the iptables rules, including the default policies for the INPUT, OUTPUT, and FORWARD chains.
To flush only the INPUT chain, you can use the -F INPUT option:
sudo iptables -F INPUT
To flush only the OUTPUT chain, you can use the -F OUTPUT option:
sudo iptables -F OUTPUT
To flush only the FORWARD chain, you can use the -F FORWARD option:
sudo iptables -F FORWARD
Note that flushing the iptables rules will remove all the rules, including the default policies and any custom rules that you have configured. This can leave your system vulnerable to network attacks if you do not set up new rules to protect it.