SystemD

#!/bin/sh
 
### BEGIN INIT INFO
# Provides: Firewall
# Required-Start:
# Required-Stop:
# Default-Start:
# Default-Stop:
# Short-Description: Starts firewall rules
# Description: Starts firewall rules
### END INIT INFO
 
# Exit immediately if a command exits with a non-zero status.
set -e
 
case $1 in
        start)
                iptables -F
                iptables -A INPUT -s 192.168.200.0/24 -j ACCEPT
                iptables -A INPUT -p tcp --dport 22 -j DROP
                ;;
        stop)
                iptables -F
                ;;
        *)
        echo "Usage: /etc/init.d/firewall.sh {start|stop}"
        exit 1
        ;;
esac

• chmod +x /etc/init.d/firewall.sh

/lib/systemd/system/firewall.service.

[Unit]
Description=Firewall
Requires=network-online.target
After=network-online.target
 
[Service]
User=root
Type=oneshot
RemainAfterExit=yes
ExecStart=/etc/init.d/firewall.sh start
ExecStop=/etc/init.d/firewall.sh stop
 
[Install]
WantedBy=multi-user.target

• systemctl enable firewall Created symlink /etc/systemd/system/multi-user.target.wants/firewall.service → /lib/systemd/system/firewall.service.

• systemctl start firewall

• systemctl stop firewall
• systemctl disable firewall

Removed /etc/systemd/system/multi-user.target.wants/firewall.service.