Scheduled Wakeup in Ubuntu

Well, this is hardly related to Tivoli, but just thought of sharing this cool stuff. I have a 5-year old desktop running Ubuntu Lucid used mainly for running scheduled jobs off of cron. So, basically it plays some music everyday for couple of hours and sits idle for the rest of the day. Ideally, I wanted to put the system on standby all the time and waking it up only when the scheduled job needs run. It is relatively easy to do it in Ubuntu (especially if your BIOS supports it).

Here are the exact steps needed on my Lucid Lynx. Please note that you need to have Kernel 2.6.22 or later for this to work.

1) Install the Power management interface tools.
sudo apt-get install powermanagement-interface
2) Copy the following code somewhere in your filesystem and save it as "suspend_x_hours.sh".

#!/bin/bash
# This script puts the system under standby mode for x hours

usage() {

echo "usage: $0 <n-hours>"

echo "where <n-hours> is the number of hours to be on standby"

exit 0

}
if [ $# -ne 1 ]

then

usage

fi

PATH=$PATH:/usr/sbin
hours=$1
echo 0 > /sys/class/rtc/rtc0/wakealarm
echo `date '+%s' -d "+ $hours hours"` > /sys/class/rtc/rtc0/wakealarm
pmi action suspend

3) Schedule the script in root's crontab. e.g the following crontab entry runs at 8PM and puts the system in sleep for 10 hours, waking it up at 6:00 AM.

00 20 * * * /home/venkat/bin/suspend_x_hours.sh 10 2>/dev/null

That's it. It takes only about 10 seconds to resume from sleep and it even restores your SSH sessions when it comes back from sleep!

Hope you find it useful.