Wireless Scheduler with Cron Job

Cron is a time-based job scheduler in Linux systems which enables users to schedule jobs (commands or shell scripts) to run periodically at certain times or dates. In this example, we'll use cron to control the wireless signal, and set it to turn on only at given time.

DD-WRT is shipped with cron support, but again we'll use our own cron daemon as it's easier for future updates and will save some flash wearing.

1. Disable DD-WRT's Cron
   From the web interface, Administration > Management, find "Cron" and disable it, then click "Apply Settings"
   
   
   
   
2. Install cron (busybox) service
   The cron is provided by busybox and should've been installed. If not, run
   opkg install busybox
   
   and create the scheduling file folder:
   mkdir /etc/crontabs
   
   Set it to run on startup by creating /opt/etc/init.d/crond with the commands:
   source /mnt/root/.profile
   kill -9 $(pidof crond)
   /opt/usr/sbin/crond
   Then run the commands:
   chmod a+x /opt/etc/init.d/crond
   ln -s /opt/etc/init.d/crond /opt/etc/init.d/S80crond
   
   
3. Create a script to switch wireless
   Now create a file /opt/usr/sbin/wireless-off.sh
   #!/bin/sh
   /sbin/ifconfig ath0 down
   
   And another one: /opt/usr/sbin/wireless-on.sh
   #!/bin/sh
   /sbin/ifconfig ath0 up
   
   On VAP enabled routers, additional interfaces like ath0.1, ath0.2...etc. also need to be taken care of:
   /sbin/ifconfig ath0.1 downand
   /sbin/ifconfig ath0.1 up
   
   The full list of wireless interfaces can be found by running
   /sbin/ifconfig
   
   Don't forget the permissions command:
   chmod a+x /opt/usr/sbin/wireless-on.sh /opt/usr/sbin/wireless-off.sh
   
   
4. Edit Cron Scheduler
   DD-WRT's wireless scheduling is available only for Broadcom routers(see picture below) but missing from Atheros builds.
   
   
   
   However, its not hard to implement this on Atheros routers with the help of cron and the scripts above.
   
   For example, to turn on wireless only from 5pm to 11pm, run
   crontab -e, which will bring you the cron job editor. Add two lines like these:
   
   0 17 * * *   /opt/usr/sbin/wireless-on.sh
   0 23,0-16 * * *   /opt/usr/sbin/wireless-off.sh
   
   Save. The wireless-on script will runs only once at 5PM(17:00) but the wireless-off script runs every hour(23:00, 0:00 ... 16:00) to ensure the wireless can still be turned off in case the router is rebooted halfway.
   
   How about turning off wireless only on weekdays?
   
   0 17 * * *   /opt/usr/sbin/wireless-on.sh
   0 23,0-16 * * 1-4   /opt/usr/sbin/wireless-off.sh
   0 0-16 * * 5   /opt/usr/sbin/wireless-off.sh
   
   Refer here for the full instructions about cron.

Posted in: cron,dd-wrt,Repost,wireless