iptables -F
iptables -P INPUT DROP
iptables -A INPUT -i lo -p all -j ACCEPT
iptables -A INPUT -m state --state RELATED,ESTABLISHED -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 22 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 25 -j ACCEPT
iptables -A INPUT -p tcp -m tcp --dport 80 -j ACCEPT
iptables -t nat -A PREROUTING -p tcp --dport 25 -j REDIRECT --to-port 5000
iptables -t nat -A PREROUTING -p tcp --dport 80 -j REDIRECT --to-port 8000
iptables -A INPUT -j DROP
iptables-save

bash -c 'iptables -F; iptables -P INPUT DROP; ...'

iptables -I INPUT 1 -p tcp -m tcp --dport 22 -j ACCEPT
while iptables -D 2 INPUT; do
  :
done
for chain in $(iptables -L -n | awk '/^Chain/ && $2 != "INPUT" { print $2 }'); do
  iptables -F "$chain"
done

iptables-apply -t 180 new.rules