Firewall

Disable firewall

Preview all iptables rules

sudo iptables -L -n

Example output

piotr@ubudesk64:~$ sudo iptables -L -n
[sudo] password for piotr: 
Chain INPUT (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0            udp dpt:53
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            tcp dpt:53
ACCEPT     udp  --  0.0.0.0/0            0.0.0.0/0            udp dpt:67
ACCEPT     tcp  --  0.0.0.0/0            0.0.0.0/0            tcp dpt:67 

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination         
ACCEPT     all  --  0.0.0.0/0            192.168.122.0/24     state RELATED,ESTABLISHED
ACCEPT     all  --  192.168.122.0/24     0.0.0.0/0           
ACCEPT     all  --  0.0.0.0/0            0.0.0.0/0           
REJECT     all  --  0.0.0.0/0            0.0.0.0/0            reject-with icmp-port-unreachable
REJECT     all  --  0.0.0.0/0            0.0.0.0/0            reject-with icmp-port-unreachable

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination         

Save existing firewall rules

sudo iptables-save > firewall.rules

Issue the following commands to stop firewall:

sudo iptables -X
sudo iptables -t nat -F
sudo iptables -t nat -X
sudo iptables -t mangle -F
sudo iptables -t mangle -X
sudo iptables -P INPUT ACCEPT
sudo iptables -P FORWARD ACCEPT
sudo iptables -P OUTPUT ACCEPT

Backup and restore rules

iptables-save > firewall.rules     #dumps rules to the file. This contains all rules just missing 'iptable' word
iptables-restore < firewall.rules  #flushes memory and loads all rules from a file

Permanent rules are in /etc/sysconfig/iptables file that is loaded each time system boots up.

ufw - the default firewall configuration tool in Ubuntu

It is developed to simplyfy iptables firewall configuration, ufw provides a user friendly way to create an IPv4 or IPv6 host-based firewall. To disable ufw, enter:

sudo ufw disable