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Fixing a Stalled Time Machine Backup

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OS X’s wonderful automated local backup system, Time Machine, is one of the main reasons I recommend Macs to people. After all, having peace of mind when it comes to your files securely backed up without needing to drag and drop files every time something changes is the perfect setup. 

Time Machine does have its faults, though. One of the most common ones is a suspended, or stalled, backup. 

In this tutorial, I’ll show you how to correct the dark path that Time Machine occasionally embarks upon. I’ll also give you tips on preventing it from happening.

Basic Fixes for a Hung ‘Preparing’ Backup

This is okay for five minutes. 15 minutes? No.

The most frustrating thing Time Machine can do, aside from lose your files—which has never happened to me—is tell you it’s Preparing [to] backup. This is a valid status message, but if it lasts more than 15 minutes, there’s a problem. 

Here’s a quick list of the reasons for Time Machine sticking in its preparation stage, along with remedies for some of them:

  • The last backup was interrupted. Don’t disconnect a drive in the middle of a backup. Always check the Time Machine menu bar icon to see if it’s spinning, which means a backup is in progress. If you don’t see the Time Machine menu bar icon, launch System Preferences, open the Time Machine pane, and check the box beside Show Time Machine in menu bar.
  • You unplugged the external Time Machine drive. Make sure to check that menu bar icon and eject the disk in Finder before unplugging it. To eject a disk, open a new Finder window and click the eject icon beside the disk in the sidebar.
  • A software update was installed in the middle of a backup, which caused it to either corrupt or overwrite some files. You can prevent this by checking the Time Machine menu bar icon before installing an update, whether it’s from the App Store or within the app.
  • You forced your Mac to shut down in the middle of a backup. Try not to do this unless things really are frozen and Command-Option-Escape doesn’t allow you to force quit the culprit.

Check for Sufficient Disk Space

Three drives, but the DeLorean is almost full.

Time Machine uses a lot of space and can take up an entire 2 TB external drive if the host machine has enough data. If the target backup disk is near full, transferring backup data will not only take longer to begin, Time Machine may have trouble navigating backups that are already on the disk.

Deleting backups of a file.

Tip: You can manually remove files from a backup in the Time Machine interface by selecting them, secondary-clicking, and selecting Delete Backup or Delete All Backups of [file-name].

If the disk is near full, don’t jump to conclusions and start deleting stuff—that will confuse Time Machine all the more. Instead, wait for Time Machine to notify you that old backups will be deleted for new ones to be created. 

If you aren’t getting notifications of this, open the Time Machine pane of System Preferences, click Options, and check the box beside Notify after old backups are deleted. Personally, I like to have these disabled because my 2 TB external drive is partitioned to allot 500 GB to Time Machine and I get too many disk is full alerts.

Last Resorts

Manually skipping and restarting a backup.

If the backup is still stuck preparing, there are some options left. Rather than spend more time waiting, stop the backup manually by clicking the Time Machine menu bar icon and selecting Skip This Backup. This may take a few minutes depending on how far indexing has gotten. 

Now, you can either start it again with by clicking Back Up Now under the menu bar icon, eject the disk, or restart the Mac. Those actions are listed in order of severity. 

Usually stopping and starting the backup works, but you may need a bit more momentum to kickstart it. If none of this works, there’s still one option: formatting the drive and starting over.

Starting Over

Formatting a drive.

Alternatively, you can start over with Time Machine to free up disk space. Just be sure you are okay with data loss, because this entails formatting the drive and you won’t be able to recover any old backups.

  1. Launch Disk Utility and select the disk or partition you would like to format
  2. Click the Erase tab
  3. Make sure the format is Mac OS Extended (Journaled). If it’s not, click the drop-down menu beside Format and select Mac OS Extended (Journaled)
  4. Assign a name to your drive and click Erase. Confirm by clicking Erase once again
  5. Launch System Preferences and open the Time Machine pane
  6. Click Select, choose the disk for backups, and click Use Disk or press Enter
  7. An initial backup will commence in 120 seconds. You can start it immediately by clicking the menu bar icon and selecting Back Up Now

Happy Future Backups

My 500 GB partition still shows backups that were taken when I first got my MacBook Pro with Retina display in August of last year. I don’t remember having a backup hang in all that time, but I’ve hidden most of the status messages from my view—Time Machine is disabled in Notification Center and the menu bar icon is hidden in Bartender

Still, frustration does happen. You should now know how to deal with it, whether you have to remove old backups, manually stop and start one, restart the Mac, or even format the backup drive and start over.

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