Guide To Excluding Data from Time Machine Backups


Brian writes: My question is about Time Machine and what NOT to include. I just installed a new 2TB HDD into my iMac and have reinstalled Snow Leopard. My Time Capsule’s hard drive is only 1 TB. Previously I backed up everything except a few large files I identified. Now I want to ensure I back up the “essentials” so I assume my excluded list in all reality should be long … real long.

FYI - I did make a Carbon Copy Clone on 2 separate disks filed away once the system and apps were totally setup. I am looking for specifics on what all to exclude and how best to do this.


Indeed, this is where Time Machine’s interface isn’t great — there’s no way to be inclusive with it, only exclusive.

You say you want to backup the “essentials” which may mean different things to different people.

If all you want is your documents and data, the lion’s share of that is stored in the /Users folder. So, in theory, you could simply go into System Preferences, choose Time Machine, click on Options, and then add every folder EXCEPT /Users from the root level of your hard drive.

This means you’ll exclude 3 (or possibly 4) folders at the root of your hard drive (assuming you haven’t added extras here): Applications, Library, System, and (possibly) Developer.

As you’re doing this, one interesting thing will happen. When you choose the folder named “System” it will prompt you and let you decide whether you only want to exclude only the “System” folder or “All System Files”, something that would be somewhat tedious to do manually, especially since so many of them are hidden from the Finder and normal file dialogs.

To get more granular on exactly what documents you backup (or exclude), you’ll have to dig into the /Users folder. Each user on the system will have a separate folder within it, of course. Inside each of those user folders you’ll likely see the following. I’ve included a quick explanation and some advice for each.

  • Applications - Any Mac apps you’ve installed for just your user. In most cases this folder is empty. If you’re not backing up apps, feel free to exclude it.
  • Desktop - The contents of your Desktop folder. Since most of us wind up storing commonly-used documents here, I highly recommend keeping this in the backup (and NOT excluding it).
  • Documents - Unless you’ve chosen to save them elsewhere, this is where all your documents will be. Keep this one!
  • Downloads - The files you’ve downloaded from the Internet. In most cases you can probably redownload these, so if you’re looking to make your backups as lean as possible, you’re probably safe excluding this one.
  • Library - All your application support files, preferences and, in some cases your user files (like Mail, iCal, Yojimbo, etc). I don’t recommend excluding this, even though that means you will be backing up more than you probably wish.
  • Movies - Any movies you’ve created with iMovie (and other third-party movie software) will be stored here. Likely large files, and likely stuff you want to safeguard in a backup.
  • Music - Your iTunes Library and any files you’ve created with GarageBand (and possibly other, third-party music software) will be stored here. The choice to back it up is yours.
  • Pictures - iPhoto, Photo Booth, and other third-party photo apps will likely store data here. Again, a user-choice.
  • Public - Most people won’t use this, but if you have File Sharing enabled this is where anyone can drop files for you to use. In most cases, safe to exclude.
  • Sites - Your personal web sharing directory. If you’ve customized your website hosted from your Mac, keep this one, otherwise probably safe for most to exclude.

Once you have excluded all of these, you should be good to go with a lean and mean Time Machine backup. Note that if you DO exclude the /System, /Library and /Applications folders from the root of the hard drive your backup will be incomplete. Should your hard drive die, you’ll have to reinstall Snow Leopard first, then restore from your Time Machine backup, and then reinstall all your third-party apps.