** User scripts **
These are shell scripts that you can create, and which will be run when 
certain events occur.  Those scripts must be saved in /jffs/scripts/ ,
so, JFFS must be enabled, as well as the option to use custom 
scripts and configs.  This can be configured under Administration -> System.
Available scripts:

* ddns-start: Script called at the end of a DDNS update process.
               This script is also called when setting the DDNS type
               to "Custom".  The script gets passed the WAN IP as 
               an argument.
               When handling a "Custom" DDNS, this script is also
               responsible for reporting the success or failure
               of the update process.  See the Custom DDNS section
               below for more information.
* dhcpc-event: Called whenever a DHCP event occurs on the WAN 
                interface.  The type of event (bound, release, etc...) 
                is passed as an argument.
* firewall-start: Firewall is started (filter rules have been applied)
                   The WAN interface will be passed as argument (for 
                   example. "eth0")
* init-start: Right after jffs is mounted, before any of the services 
               get started
* nat-start: nat rules (i.e. port forwards and such) have been applied 
              (nat table)
* openvpn-event: Called whenever an OpenVPN server gets
                  started/stopped, or an OpenVPN client connects to a
                  remote server.  Uses the same syntax/parameters as
                  the "up" and "down" scripts in OpenVPN.
* post-mount: Just after a partition is mounted
* pre-mount: Just before a partition is mounted.  Be careful with 
              this script.  This is run in a blocking call and will 
              block the mounting of the partition  for which it is 
              invoked till its execution is complete. This is done so  
              that it can be used for things like running e2fsck on the 
              partition before mounting. This script is also passed the 
              device path being mounted as an argument which can be 
              used in the script using $1.
* qos-start: Called after both the iptables rules and tc configuration 
              are completed for QoS.  This script will be passed an
              argument, which will be "init" (when QoS is being
              initialized and it has setup the tc classes) or
              "rules" (when the iptables rules are being setup).
* services-start: Initial service start at boot
* services-stop: Services are stopped at shutdown/reboot
* unmount: Just before unmounting a partition.  This is a blocking 
            script, so be careful with it.  The mount point is passed 
            as an argument to the script.
* wan-start: WAN interface just came up (includes if it went down and 
              back up).  The WAN unit number will be passed as argument 
              (0 = primary WAN)

Don't forget to set them as executable:

   chmod a+rx /jffs/scripts/*

And like any Linux script, they need to start with a shebang:

   #!/bin/sh