It’s fairly well accepted by most commenters at this point that Time Machine may be one of the biggest features to be part of Leopard. Even those users who managed their own backup solutions – and many still do, including myself – applaud it for making backups both easy and intuitive for the average end user. (I credit it for having dramatically reduced panicked phone calls from friends and family about missing files, and that alone made the effort of updating oh-so worth it.)
However, many of us would also like ways to change the frequency of its backups. By default, Time machine runs once an hour, saving a daily backup at the end of the day and a weekly backup at the end of the week. This behavior continues until the drive it was pointed to is full, at which point it begins to delete the oldest backups. Almost immediately, people wanted a way to change the frequency – even if, like me, half the reason was the annoyance of those bright-blue, flashy LED’s on the external hard drive as it spins up every hour in the middle of the night.
An earlier hint at Mac OSX Hints had users editing a .plist file to change the frequency of backups. This hack consisted of editing com.apple.backupd-auto.plist, specifically the following lines:
A change to that integer value – which is in seconds, by the way – and Time Machine would theoretically back up on your schedule, not Apple’s. However, that seems to cause more problems than it solved, in my experience. Specifically, now Time Machine backs up whenever it likes. (It seems to be about once a day, give or take an hour or so, not once every three hours, as I set it to be.) Upon inspection, it appears that the file’s permissions are broken. Repairing permissions in Disk Utility hangs, and attempting to manually do so, even on a duplicate, causes Finder to crash.
…Let’s just say that method is Not Recommended, then.
Alternatively, there is now this – Time Machine Scheduler. Time Machine Scheduler does not meddle with the .plist files – it simply runs its own daemon to create a backup. It can be set for any length of time between 1 and 12 hours, as well as optionally running a backup upon loading. You have the option of either installing Scheduler and its daemon, in which case you do not need to open TMS, or simply running it from the .app when you want to make a backup. It is also fully compatible with existing Time Machine backups – the preference pane will show that Time Machine is off, but it reads the TMS-created backup and date of last backup without trouble.
There is also the option to mount and unmount the Time Machine backup drive automatically, although I have not tested this. (I have a partitioned drive, and the other partitions are in frequent use, so I don’t bother.)
This method works very well for me, at a reliable three hours. It takes the same amount of time to run backups, as well as to load and unload the normal Time Machine interface, and, thank heavens, it actually does it every three hours. Why Apple didn’t include the option to change the backup frequency all along boggles me.
I will note that a third way to do this is to use Lingon to edit the plist files. I have not tried it, but I thought I would mention it, for those who might be interested. How about you? Have you tried Lingon? Time Machine Scheduler? Did the original .plisthack work for you?
(Time Machine Scheduler and Lingon are both free utilities, available at the links above.)