save iptables rules only when they change

installers/common.sh

@@ -145,14 +145,18 @@ function configure_exit() {
 		sed -i 's#\#ifaddr=#ifaddr=172.16.0.1/16#g' /var/lib/lokinet/lokinet.ini
 		sed -i 's#\#paths=6#paths=8#g' /var/lib/lokinet/lokinet.ini
 		sed -i 's#\#net.ipv4.ip_forward=1#net.ipv4.ip_forward = 1#g' /etc/sysctl.conf
-		if [ -z $(grep "172.16.0.1/16" "/etc/iptables/rules.v4") ]; then iptables -t nat -A POSTROUTING -s 172.16.0.1/16 -o eth0 -j MASQUERADE; fi
+		if grep -Fxq "172.16.0.1/16" /etc/iptables/rules.v4
+		then
+		    echo -n "iptables entry already exists"
+					else
+				iptables -t nat -A POSTROUTING -s 172.16.0.1/16 -o eth0 -j MASQUERADE
+				iptables-save > /etc/iptables/rules.v4
+		fi
 #		iptables -t nat -A POSTROUTING -s 172.16.0.1/16 -o eth0 -j MASQUERADE
-		iptables-save > /etc/iptables/rules.v4
 		sudo sysctl -p /etc/sysctl.conf
 		sudo systemctl restart lokinet
 
 		#clean out installer files
-		# sudo rm -r $exit_dir/installers || install_error "Unable to remove installers"
 		sudo rm -r /tmp/microexit || install_error "Unable to remove /tmp/microexit folder"
 
 		#provide option to launch and display lokinet address