10. Creating Startup Scripts

#! /bin/sh

# If no rules, do nothing.
[ -f /etc/gateway.rules ] || exit 0

case "$1" in
    start)
        echo -n "Turning on packet filtering:"

    	/sbin/modprobe ip_masq_ftp #only if using ipchains
    	/sbin/modprobe iptable_nat #only if using iptables
    	/sbin/modprobe ipt_MASQUERADE #only if using iptables
        /sbin/ipchains-restore < /etc/ipchains.rules || exit 1

        echo 1 > /proc/sys/net/ipv4/ip_forward
    	# for RedHat users, the above line is not needed if you have
    	# FORWARD_IPV4=true in /etc/sysconfig/network file

    	echo "1" > /proc/sys/net/ipv4/ip_dynaddr
    	# the above option is for Dynamic IP users (DHCP,PPP or BOOTP)

        echo "."
        ;;
    stop)
        echo -n "Turning off packet filtering:"
        echo 0 > /proc/sys/net/ipv4/ip_forward

        /sbin/ipchains -F
        /sbin/ipchains -X
        /sbin/ipchains -P input ACCEPT
        /sbin/ipchains -P output ACCEPT
        /sbin/ipchains -P forward ACCEPT
        echo "."
        ;;
    *)
        echo "Usage: /etc/init.d/gateway {start|stop}"
        exit 1
        ;;
esac

exit 0

bash# chmod 744 /etc/init.d/gateway