Change what Time Machine backs up

Time Machine used to be a mess. I would try it with each new macOS release, get frustrated, and give up. My incoming email from readers was sometimes dominated by Time Machine problems, particularly when Apple transitioned from HFS+ to APFS as the Mac’s default startup volume file system. At one point, Time Machine volumes had to be formatted as HFS+ even after APFS became the default startup volume format.

Which is why I’m so pleased that Time Machine generally—generally, mind you—now performs as I would expect as part of my backup-and-archive systems.1 I use Backblaze for encrypted Internet-hosted backups, Carbon Copy Cloner for nightly local clones, and Time Machine for continuous archiving and backups. I also use Dropbox and iCloud Drive for nearly all of my documents.

Often, however, I want to exclude something—or a lot of somethings—from Time Machine. A file or folder is too big (like Parallels virtual machines), a volume contains a clone of another volume (and thus should be ignored), or some data changes so frequently that it’s not ideal to archive using Time Machine.

Here’s how you can control what Time Machine archives.

Via the main System Settings interface

Use System Settings to exclude files, folders, or volumes from Time Machine backups.

Open System Settings and go to General: Time Machine. Click Options. The Exclude from Backups list shows everything you’ve added, and anything Apple has included. You can drag items in or click the + (plus) icon to open a file or folder (or volume) selector. Select an item and click – (minus) to remove it.

As you can see from my list, I have many external volumes, and all of them are excluded from Time Machine—all external volumes are added to this list by default, and I’ve left it that way. After many, many hard disk drive failures, including a mirrored RAID, I no longer own enough local capacity to back up all my volumes. I put less-critical files on external volumes and rely on Backblaze.

You may also note that a couple of external volumes have Time Machine icons. Those are included in Time Machine by default, and if you select one, the – (minus) icon is grayed out. Typically, the only entry besides those volumes Apple automatically includes is /Users/Shared/adi, which is related to Apple’s digital commerce—that folder can be removed from exclusions, but I don’t know any good reason to.

Dial in your Time Machine exclusions

You can use tmutil on the command line to get quick answers about what Time Machine will back up or exclude.

If you’re comfortable with the command line, you can also get to know tmutil, which provides text-based control over the same features presented in the Time Machine settings, plus quite a lot else. (In all of these examples, replace /path/to/item or similar with the actual path, of course!)

For instance, if you want to exclude a file or folder, but also may want to move that item later, use:

tmutil addexclusion /path/to/item

Wherever you relocate that item to, the exclusion follows. Or, if you want to use a fixed path and make sure it is invariant, same as the Exclude from Backups, use:

sudo tmutil addexclusion -p /absolute/path/to/item

The sudo command will prompt you to enter an administrative password because it requires elevated system privileges. The -p flag forces the time machine to excluse a path rather than a file.

A neat tip, if you didn’t know it: you can use the Finder to copy absolute paths for items:

In the Finder, select a file or folder.

Hold down the Option key and choose Edit.

Note the Copy “name” as Pathname option: choose it. You can also press Command-Option-C.

The Clipboard stores a path that can be quite short for a local volume, or verge on the absurd for files or folders on iCloud Drive, Dropbox, Google Drive, or other cloud-accessible systems. For instance, take a gander at:

/Users/glenn/Library/Mobile\ Documents/com\~apple\~CloudDocs/Aperiodical\ Projects\ \(iCloud\)/Flong\ Time\ No\ See\ Book/Figures/01\ Flong\ Time/flongs-per-year-chart.png

If you’d like to use the command line to check on items that are excluded or included, you can use:

tmutil isexcluded /path/to/item

You can use shell-based wildcard expansion, too, so if you did a lot of fussing with inclusion and exclusion in nested folders, you can enter the first part of the path, like ~glenn then use ./* to get a list with [Excluded] or [Included] before each directory at that level of the path, like tmutil isexcluded ~glenn/*.2

For further reading

Joe Kissell has written loads about Time Machine in Take Control of Backing Up Your Mac, including strategies, complements, and alternatives.

[Got a question for the column? You can email glenn@sixcolors.com or use /glenn in our subscriber-only Discord community.]

Some people still have terrible experiences with it, but I receive so much less email about Time Machine, and have had so many fewer problems, that I can rate it “not a complete mess” now. ↩

These shell-based expansions are processed by the bash or other shell that handles the command-line interface. They’re passed to the command. But it means you can use any typical expansion with tmutil. ↩