While we have endeavoured to make the firewall very flexible and configurable, there may be times when you need to make custom modifications beyond the capabilities of fwadmin. The firewall allows you to add extensions to some of the automatically generated configuration files, by putting these extensions in files in the directory /usr/local/custom (usually with the same name as the file to be extended). For example, the file /usr/local/custom/rc.local can contain extensions to the /etc/rc.local file.