Open /etc/nftables.conf in write mode

firewall.py

@@ -204,6 +204,6 @@ if __name__ == "__main__":
     if args.export:
         print(template.render(nat=nat, ports_openings=ports_openings, ports_openings_adh=ports_openings_adh))
     else:
-        with open('/etc/nftables.conf') as nftables:
+        with open('/etc/nftables.conf', 'w') as nftables:
             nftables.write(template.render(nat=nat, ports_openings=ports_openings, ports_openings_adh=ports_openings_adh))
         subprocess.run(['systemctl', 'reload', 'nftables'])