Restore Individual Files

The easiest problem to recover from is a small number of files that are missing, or for which you need an older version. Follow these steps:

1. If you backed up the files using Time Machine, try restoring them using the steps in Restore Data with Time Machine; or, if you used another versioned backup app, follow the developer’s instructions (check the Help menu) for restoring your files.

2. If the files are missing from your backup, check your bootable duplicate. Connect the drive (if it’s not already attached) and navigate to the location on the disk where the file should be. If it’s there, copy it to your main disk.

3. If steps 1 and 2 don’t work—for example, if your entire backup drive is missing—move on to your secondary backup. That may mean fetching an extra backup drive from another location and following steps 1 and 2 again, or using your internet backup app to find the file in your online backup.

Use Your Bootable Duplicate

In some situations it’s clear that your problem is worse than a few missing files. If your Mac won’t start up—it gets stuck at a blue or gray screen or displays a flashing question mark icon—turn next to your bootable duplicate. Also use your duplicate if many files seem to be missing or damaged, apps won’t launch, you’re unable to start the Mac using macOS Recovery, or it exhibits other similar system-wide misbehavior. Follow these steps:

1. Attach the drive containing your bootable duplicate. (Remember, it must be directly attached to your Mac; you can’t boot from a duplicate over a network.)

2. If your Mac is already running, restart it; if not, turn it on. Immediately (or as soon as it begins restarting) press and hold the Option key.

3. When your screen shows the volumes available for booting your Mac, release the Option key, use the arrow keys to select your duplicate, and press Return. Your Mac should boot from the duplicate—but be aware that this may take considerably longer than booting from your regular internal startup disk. (And if your backup drive uses a slow interface, such as USB 2.0, it will take longer still.)

   Once your Mac finishes booting, you can continue working from your duplicate if you want to. But if possible, you should check your internal drive and repair it.

4. Run Disk Utility (in /Applications/Utilities on your duplicate). Select your internal disk in the list on the left. In the First Aid view, click Repair Disk. Disk Utility attempts to fix the disk. If it succeeds, you can restart your Mac right away, and you’ll automatically go back to using your internal disk. If Disk Utility is unable to repair the disk, you have three options:

   • Try a third-party disk repair utility, such as Alsoft’s DiskWarrior. (Note that as of publication time, DiskWarrior is not yet capable of rebuilding APFS volumes, which are used for all boot volumes under Mojave and for SSD boot volumes under High Sierra, but the developer is working on adding full APFS support.)

   • Erase the internal disk and then reverse the duplication process.

   • Restore your entire disk using Time Machine (or another backup app, if you made a versioned backup of the entire disk).

   If you decide to take the second route—restoring your disk from a bootable duplicate—read on for instructions. For help restoring an entire disk from a Time Machine backup, refer back to Restore a Disk Using Time Machine.

Restore a Disk from a Bootable Duplicate

If your internal hard drive has become so badly damaged that it can’t be repaired by disk utilities—or if your hard drive, or your entire Mac, had to be replaced—your best bet is to erase the damaged drive and then restore its entire contents. Although you can restore your disk from a Time Machine backup, the process usually takes a very long time—and of course it won’t include any files you excluded from Time Machine. A better tactic, assuming you have a functioning and up-to-date bootable duplicate, is to restore your disk from the duplicate.

To restore the contents of your bootable duplicate to your internal disk, follow these steps:

1. Follow steps 1–3 under Use Your Bootable Duplicate (just previously) to start up from the duplicate.

2. Open Disk Utility (in /Applications/Utilities).

3. Select your computer’s internal disk in the list on the left.

4. In the Erase view, click Erase, and confirm that you really want to do that. Disk Utility erases the disk.

5. Follow the steps in Create and Use a Bootable Duplicate to copy the contents of your duplicate back onto your internal disk—but in this case, choose the external disk containing your duplicate as the source and your internal disk as the destination.

6. When the restoration is complete, restart from your internal disk.

7. Allow data (particularly files you added or modified since you last updated your duplicate) to sync from the cloud using services such as iCloud Drive, iCloud Photo Library, and Dropbox; this reduces the number of items you’ll need to find in your backups. (See Can Cloud Sync Simplify Backups?)

8. If you have further files to restore that weren’t synced from the cloud, and your versioned backup software (Time Machine or otherwise) ran after the most recent update of your bootable duplicate, you may want to use that software now to copy any new or changed files back to your main disk. Unfortunately, most backup apps (including Time Machine) have no way to select only files that changed after a specified date and time—namely, those that changed and were backed up after you last updated your bootable duplicate. See the sidebar Finding Recently Backed-Up Files, ahead.

After you restore a bootable duplicate in this manner, Time Machine may conclude that all the files on your disk have changed and try to create an additional copy of all of them. Read the sidebar Restarting Time Machine Backups After a Restore, earlier, for more details and a possible solution.