Ruby, Rails, OSX and Linux fun

First of all, what do I mean by safe sleep, fast sleep or hibernate?

Safe sleep is the way OSX sleeps to RAM and as well create a sleepimage (which is the size of your RAM). In case you run out of battery, so you can still resume from the image if the battery is dead, (and you have plugged it in   Provides very fast wake up, uses the battery while sleeping.

Fast Sleep is just sleep to RAM, same as safe sleep but no image creation, and if your battery is dead, the mac will cold boot. Provides very fast wake up same as safe sleep, uses the battery while sleeping.

Hibernate is when it uses the sleepimage all the time. Slower sleep and slow wake up, but it does not use battery at all…

So…

I found in this website http://alt.cc/jk/2007/08/07/safe-sleep-addendum/ this nice script that handles when to FastSleep or when to Hibernate.

you can get safe sleep with the command “$ sudo pmset hibernate 3″

I have modified the script it little :

#!/bin/sh
MODE=`/usr/bin/pmset -g | grep hibernatemode | awk '{ print $2 }'`
LEFT=`/usr/bin/pmset -g batt | grep Internal | awk '{ print $2 }' | awk -F % '{ print $1 }'`
HIBERNATE=20
FASTSLEEP=50
echo "Running safesleep.sh => MODE: ${MODE} LEFT: ${LEFT}" >> /var/log/system.log
if [ $LEFT -lt $HIBERNATE ] && [ $MODE != 3 ] ; then
	{
		echo "Less than ${HIBERNATE}% remains" >> /var/log/system.log
		echo "Setting Hibernate (hibernate mode 1)" >> /var/log/system.log
		`/usr/bin/pmset -a hibernatemode 1`
		LS=`ls -al /private/var/vm/sleepimage`
		echo "The sleepimage should be created:" >> /var/log/system.log
		echo "${LS}" >> /var/log/system.log
	}
elif  [ $LEFT -gt $FASTSLEEP ] && [ $MODE != 0 ]; then
	{
		echo "Greater than ${FASTSLEEP}% remains" >> /var/log/system.log
		echo "Setting FastSleep (hibernate mode 0)" >> /var/log/system.log
		`/usr/bin/pmset -a hibernatemode 0`
		`rm -rf /var/vm/sleepimage`
	}
fi

save it as /Users/your_user_name/.crons/safesleep.sh

now make it permanent in a crontab to run every 10 minutes, but wait, anacron (osx default cron) only supports daily/weekly/monthly jobs! (unless you patch it)

I guess we’ll have to install fcron:

$ sudo port -d install fcron

$ sudo vi /opt/local/etc/fcrontab


@,runas(root) 10 sh /Users/your_user_name/.crons/safesleep.sh


$ sudo launchctl load -w /Library/LaunchDaemons/org.macports.fcron.plist

$ sudo launchctl start org.macports.fcron

that’s it.

enjoy