Customize Time Machine Settings

I find the hourly backups performed by Time Machine to be a bit excessive for my needs, and wish the Time Machine preferences offered more flexibility. My backup device is a high-capacity hard drive attached to a first-generation AirPort Extreme (802.11n), and I don’t like to ask the drive to spin up on the hour, as good evidence suggests excessive spinning up and spinning down lessens the life of a hard drive. This is much less of a concern with the Apple Time Capsule, which contains an enterprise-grade hard drive that’s more durable than the average drive.

I feel like Apple didn’t get the balance between usability and configurability quite right with the Time Machine preferences. The system is certainly easy to configure, but it’s just too simple. After reading a hint at www.macfixit.com, I did some hunting around the typically forbidden areas of my hard drive, which yielded some property lists stored in /System/Library/LaunchDaemons: com.apple.backupd.plist; com.apple.backupd-auto.plist; com.apple.backupd-wake.plist; and com.apple.backupd-attach.plist. These files can be opened in TextEdit (in your Applications folder), and for my purposes I wanted simply to change the backup interval to every 24 hours. If you open com.apple.backupd-auto.plist in TextEdit, you’ll see this:

To change the interval to every twenty four hours, change the 3600 line to 86400 and save the file. The value in that line is the number of seconds between backups. 3600 seconds is one hours, 86400 seconds is one day. Simply save that file, log out, log back in, and you’re all set.

Time Machine is actually quite configurable when you’re brave enough to edit those property lists. While I cannot guarantee the reliability of these two utilities nor support them, their extensive configurability has proven useful for me:

Time Machine Scheduler: http://www.klieme.com/TimeMachineScheduler.html
Time Machine Editor: http://timesoftware.free.fr/timemachineeditor/