What to Do When Time Machine Is Stuck on "Preparing Backup"

Time Machine has many tricks up its sleeve to ensure error-free backups, as well as backups that take as little time as possible to complete. In some cases, these two goals can force Time Machine to take a long time preparing for a backup to begin.

Time Machine uses an inventory system that OS X creates as part of the file system. In essence, any file that has been changed in any way is logged. Time Machine can compare this log of file changes against its own inventory of files. This log comparison system allows Time Machine to create incremental backups, which generally don’t take much time to perform, while still maintaining a complete backup of your files.

Normally, unless you’ve made major changes or added a number of new files to your drive, the "preparing backup" process is very quick. In fact, it's so quick that most Time Machine users never notice it, except for the very first Time Machine backup, where the preparation phase does indeed take a long time.

If you see a very long preparation phase, or Time Machine seems to be stuck in the preparation process, this guide should help you fix the problem.

Time Machine "Preparing Backup" Process Takes Too Long

Check to see if the preparation process is stuck:

  1. Launch System Preferences by clicking its Dock icon, or selecting System Preferences from the Apple menu.

    System Preferences in Apple Menu and in the Dock on macOS Desktop
  2. Open the Time Machine preference pane by clicking its icon in the System area of the System Preferences window.

    Time Machine icon in System Preferences app in macOS
  3. You will see either a "Scanning xx items," "Preparing xx items," or “Preparing backup” message, depending on the version of OS X you're running.

  4. The number of items in the message should be increasing, even if it does so slowly. If the number of items remains the same for more than 30 minutes or so, then Time Machine is probably stuck. If the number increases, or the message changes, then Time Machine is working correctly.

  5. If the number of items increases, be patient and don't interrupt the preparation phase.

  6. If you think Time Machine is stuck, give it another 30 minutes, just to be sure.

What to Do If Time Machine Is Stuck in the "Preparing Backup" Process

  1. In older versions of macOS, you could turn Time Machine off by sliding the on/off switch in the Time Machine preference pane to the Off position. You can also just click the Off side of the switch.

    Now, in macOS Mojave, there is only a checkbox to turn off automatic backups. It's unclear whether this does the same as toggling Time Machine to Off.

    Back Up Automatically checkbox in Time Machine preferences in macOS Mojave

    Still, the following may be useful in tracking down your issue.

  2. Once Time Machine is turned off, check the following as possible causes of the problem:

If you use any type of antivirus or malware protection system, make sure the application is set to exclude the Time Machine backup volume. Some antivirus apps won't allow you to exclude a disk volume; if that's the case, you should be able to exclude the "Backups.backupdb" folder on the Time Machine backup volume.

Spotlight can interfere with the Time Machine preparation process if it's performing an index of the Time Machine backup volume. You can prevent Spotlight from indexing the Time Machine backup volume by adding it to the Privacy tab of the Spotlight preference pane as follows:

  1. Launch System Preferences by clicking its Dock icon, or selecting System Preferences from the Apple menu.

  2. Open the Spotlight preference pane by clicking its icon in the Personal area of the System Preferences window.

    Spotlight icon in System Preferences app in macOS
  3. Click the Privacy tab.

    Spotlight preferences panel, highlighting Privacy tab and Add (plus) button
  4. Either drag-and-drop your Time Machine backup volume to the list of locations that will not be indexed, or use the Add (+) button to browse to your backup folder and add it to the list.

Remove the .inProgress File

Once you prevent Spotlight and any antivirus apps from accessing your Time Machine backup volume, it’s almost time to try the Time Machine backup again. But first, a bit of manual cleanup.

  1. With Time Machine still turned off, open a Finder window and navigate to: /TimeMachineBackupDrive/Backups.backupdb/NameOfBackup/

  2. This path needs a bit of explaining. TimeMachineBackup is the name of the drive you're using to store your backups on. In our case, the Time Machine drive name is Tardis.

  3. Backups.backupdb is the folder where Time Machine is storing the backups. This name never changes.

  4. Finally, the NameOfBackup is the computer name you assigned to your Mac when you first set your Mac up. If you've forgotten the computer name, you can find it by opening the Sharing preference pane; it will be displayed near the top. In our case, the computer name is Tom’s iMac. So navigate to /Tardis/Backups.backupdb/Tom’s iMac.

  5. Within this folder, look for a file named xx-xx-xx-xxxxxx.inProgress.

  6. The first 8 x’s in the file name are a placeholder for the date (year-month-day), and the last group of x’s before the .inProgress is a random string of numbers.

  7. The .inProgress file is created by Time Machine as it gathers information about the files it needs to back up. You should delete this file if it exists, as it may contain out-of-date or corrupt information.

  8. Once the .inProgress file is removed, you can turn Time Machine back on.

Other Causes of Long Time Machine Backup Preparation Times

As mentioned above, Time Machine keeps track of which files have been updated and need to be backed up. This file system changelog can become corrupt for various reasons, the most likely being unexpected shutdowns or freezes, as well as removing or turning off external volumes without ejecting them properly first.

When Time Machine determines that the file system changelog isn't usable, it performs a deep scan of the file system to build a new changelog. The deep scan process greatly extends the time it takes to prepare Time Machine to perform a backup. Luckily, once the deep scan is complete and the changelog is corrected, Time Machine should perform subsequent backups in a normal fashion.

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