How to make Time Machine backup less (or more) frequently.
Apple’s Time Machine is a useful beast. Plug a disk into your Mac or buy a Time Capsule and Time Machine does the rest — waking up once an hour and copying anything that’s changed onto your backup.
However, you may not want a backup every hour — the backup disk is a limited resource. If you’re regularly changing large files then Time Machine is regularly writing large amounts of data to the backup disk, and if that’s the case then you won’t have backups going back very far into the past.
So there will be lots of revisions of files that have changed recently, but nothing much from, say, a couple of months ago.
So how do you change the interval?
The standard Time Machine options don’t allow you to change the backup interval (the time between backups), but the preferences are there to be changed if you know how.
From the command line
If you don’t want to install any extra software then you can change Time Machine’s backup interval from a shell prompt. Start up a Terminal window and then type:
sudo defaults write /System/Library/LaunchDaemons/com.apple.backupd-auto StartInterval -int 18000
The 18000 above is the required backup interval in seconds — five hours in this example. And note that the above command is all on one line.
Point-and-click
There are several full Mac OS applications out there that allow you to manipulate Time Machine’s hidden preferences. The two most popular are Time Machine Scheduler and Time Machine Editor. I haven’t used either (being someone who leans toward using the command line), but they look like they’ll do the job. However…
My recommendation was, but is no more:
I did suggest using the Secrets prefPane to change Time Machine’s backup interval (see below), but unfortunately that turned out to be bad advice. You can set the interval using the Secrets prefPane but it doesn’t stick. Quit the System Preferences application and start it up again and you’ll find the interval has gone back to the default of 3600 seconds.
So it seems Secrets prefPane doesn’t work for this after all! I’ll leave the rest of this article in place and perhaps someone will tell me when the problem’s fixed?
In the mean time, please use one of the options suggested above.
Here’s the rest of the original article, which at the moment doesn’t work:
I suggest you use the Secrets Prefpane from blacktree. Just download it from the link near the top of the web page, unzip it and then install it by double-clicking on the resulting file (Secrets.prefPane).
Now, when you start up System Preferences you’ll find a new preferences pane:
The Secrets preferences pane allows you to set the hidden Time Machine backup interval:
but — and this is why I recommend the Secrets prefPane – it also allows you to change all sorts of other hidden preferences in Mac OS:
which is great fun — and who knows, may even prove useful 
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Secrets prefs for TimeMachine don’t appear to work for me.
It doesn’t change the 1 hr. backup interval. Doesn’t appear to presist the new value (3600 default) is always present after launching Preferences – Secrets.
Odd — so you set the interval to something different, come out of the Secrets prefPane, go back in and the number has gone back to 3600?
I read your posting, installed Secrets and had the same result: no changes. Every time you re-open Secrets it’s reverted back to the 3600 setting. Even more vexing is if you try and edit the file (as written up on other sites) I get a message telling me that I don’t have the authority to change the file. And here I thought I paid for the computer! Despite following Apple sites directions I still couldn’t get the file to allow me to edit it to allow me to change the interval.
I purchased my MacBook Pro because I thought Apple was better. After 4 months I regret my decision on an almost daily basis.
A thought: does your account have administrator privileges? If you go to System Preferences->Accounts and click on your account, is ‘Allow user to administer this computer’ ticked?
Mark
Thanks for the post in response to my comment. Yes it is ticked. Your explanation is clearer than Apples but neither results in being able to edit the file that other sites refer to.
I did download Time Machine Scheduler and am trying it out. I can’t figure out if it’s working–haven’t paid attention to the actual backup times–but the last I checked it’s still scheduled for an hour interval.
This is truly frustrating and again: I’m very disappointed in Apple. It’s as though they hired some cast-off Microsoft employees and their viral thinking has infected the company.
It seems I’ve been giving bad advice. Secrets prefPane doesn’t work for me either now I try it again. I must have changed my backup interval by a different route before installing the prefPane and so not noticed that the Secrets prefPane Time Machine settings don’t stick. Sorry — I’ve amended the article accordingly
Mark
Maybe my time machine is strange but it doesn’t work for me?
I believe I have an understanding of why solutions such as Secrets prefPane don’t appear to be working.
The time interval for a Time Machine backup is declared in a launchd plist file. However, you have to restart your machine for any interval changes to take effect – the launchd daemon interval won’t change otherwise. This is true even for your command line solution, and might be why other programs (such as the Secrets prefPane) still “see” the old value, even after (apparently) applying the change.
Think of system launchd plist files like the old AUTOEXEC.BAT and CONFIG.SYS files of MS-DOS. Changes to those files wouldn’t have any immediate effect on how the system was running – you had to restart the computer in order to see the effects of those changes. The launchd plist files for Time Machine work the same way.
There seems to be a fair amount of misinformation on the internet, related to confusion over why the interval change doesn’t take effect immediately. (Even the authors of TimeMachineScheduler seem confused about this, in the first description paragraph on their program’s website – which gives me cause to seriously question the validity of their software offering.) It’s easier to understand once you know how launchd works.
To confirm this, I used the excellent open-source program Lingon (http://tuppis.com/lingon/) to modify my plist file for Time Machine, setting the interval to every two hours instead.
After rebooting, the Time Machine UI still erroneously thinks backups will be happening every hour (this is apparently hard-coded, and make it appear that the interval change had no effect), but the backups themselves take place every two hours, just as I instructed!
(Oh, and “Michael” – I’m sorry, but your over-the-top anti-Apple comments make it difficult to take you seriously.)
Lingon is now no longer available. Why is it so darn difficult to change the interval? Seems like Apple doesn’t want people changing it. Lame.
Mark,
Thanks for the command line instructions. I am completely ignorant of this guru type stuff, but never the less followed your instructions. But how do I know if it did anything (other than waiting and watching for five hours)? Thanks.
This is cool but what if I want to schedule a specific time, say 1:00am for my Time Machine to backup? Can I run it off some cron job instead of its own scheduler?
Nevermind: Time Machine Editor can do it… Supposedly… We’ll see…