To delete firewall rules on a Linux system, you can use the iptables command. The iptables command is a user-space utility that allows you to configure the Linux kernel's built-in firewall.
To delete a specific firewall rule, you can use the -D flag followed by the chain and the rule number. For example, to delete the third rule in the INPUT chain, you can use the following command:
$ iptables -D INPUT 3
To delete all the rules in a specific chain, you can use the -F flag followed by the chain name. For example, to delete all the rules in the INPUT chain, you can use the following command:
$ iptables -F INPUT
To delete all the rules in all chains, you can use the -F flag without specifying a chain name. For example:
$ iptables -F
Note that these commands will only delete the rules from the firewall, but they will not delete any custom chains that were created. To delete a custom chain, you can use the -X flag followed by the chain name. For example:
$ iptables -X mychain
This will delete the custom chain named "mychain" from the firewall.
For more advanced usage of the iptables command, you can refer to the iptables man page by running man iptables on the command line.