Schedule regular wakeups of your local machines using Wake-On-Lan

I’ve recently discovered, that my NAS’s rtc-clock is only capable of scheduling wakeups up to 1 day into the future – unsuitable for tasks that should be scheduled on a week granularity (e.g. regular offsite backups). So disorganizer was born, two small scripts that allow my NAS to request regular, scheduled wakeups from my router using WakeOnLan packages.

Limitations: I’m using a cronjob, so accuracy is limited to minute granularity. The script tries to rather wake machines early than late.

I use it to as a simple companion to Autosuspend.

Prerequisites

An openwrt-router, running uhttpd, with lua=/=luaposix.

Installation

Copy disorganizer-cron.lua to your device and make it executable: chmod +x Copy disorganizer-cgi to uhttpd’s cgi-root (default: /www/cgi-bin/), and chmod it as well.

Then add a suitable crontab line:

# /etc/crontab/nobody
* * * * * /path/to/disorganizer-cron.lua 60 /tmp/wolwakeups

Then reload cron: /etc/init.d/cron restart

Configuration

The script has minimal configuration, which spans across disorganzier-cgi and the crontab:

-- disorganizer-cgi:
-- We drop permissions. By default, the cgi runs as root, but nobody seems to
-- be a saner choice... If you want, you can use a different user here
local RUNUSER = "nobody"
-- Directory to store the wakeup events
local WAKEUP_DIR  = "/tmp/wolwakeups"

Cron and CGI should run as the same user, the WAKEUP_DIR is passed as the second parameter to the cron-script.

* * * * * /path/to/disorganizer-cron.lua 60 /tmp/wolwakeups

Beyond the directory, the cron-script receives its scheduled period (as the first parameter, in seconds, so as the example schedules with minute granularity it is 60 seconds per period) to make sure that it can wake up all pending tasks early.

Scheduling a wakeup

Wakeup requests can then be scheduled using HTTP-POST requests, for example using this curl request:

curl --data "mac=XX:XX:XX:XX:XX:XX" --data "timestamp=$(date '+%s' -d  '+ 2 minutes')" http://192.168.1.1/cgi-bin/disorganizer-cgi

Parameter mac is the Mac-address to wake, timestamp is the scheduled wakeup time as a unix timestamp in seconds since epoch (UTC).

License

All code is available under the terms and conditions of the AGPL3 license, because all the best things in life are free, and want to stay that way. For more details please see the LICENSE file.

Trivia

Within Terry Pratchetts books, the Dis-Organizer is a personal organizer that can perfom various tasks including (possibly, if all works out) reminding its owner of certain tasks. It occasionally works :P