Cron jobs are useful to repeat things on configurable intervals. E. g. reconnect your WAN connection at a given time.

You may know some more useful tasks for cron on your Wrt router.

• A standard OpenWrt Kamikaze release

Crond

is installed and running by default. Follow the testing section below and if your test fails try this:

It may be that cron is not autostarting.

  ps -elf | grep cron

If crond, the cron daemon is running, you will see:

 1760 root        380 S   crond -c /etc/crontabs -b
 2260 root        292 S   grep cron

If you do not see the crond running then ensure the cron system gets stated at boot-time.

/etc/init.d/cron start
/etc/init.d/cron enable

Create a minute job in the root crontab file:

echo "* * * * * echo \"Testing crond...\" | /usr/bin/logger -t crond" >> /etc/crontabs/root

Run

logread -f

and after a minute you should see:

Jan  1 02:50:01 OpenWrt cron.notice crond[566]: USER root pid 577 cmd echo "Testing crond..." | /usr/bin/logger -t crond
Jan  1 02:50:01 OpenWrt user.notice crond: Testing crond...

The cron jobs are defined in the

/etc/crontabs/root

file.

crond

reads this file. You have two ways on adding a cron job to this file.

The first one is just to create the

root

file with

echo

like this:

echo "0 4 * * * ifdown wan && sleep 2 && ifup wan" >> /etc/crontabs/root

or use

crontab -e

(calls the

vi

editor) to edit the cron job file. Copy & paste

0 4 * * * ifdown wan && sleep 2 && ifup wan

then hit

ESC

and enter

:wq

to save the file.

The example cron job reconnects your WAN connection at 4am every day.

When done you can list the cron jobs with

crontab -l

0 4 * * * ifdown wan && sleep 2 && ifup wan

That's it.

• Cron job calculator
  - http://www.csgnetwork.com/crongen.html