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 to prepare to start a backup.
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 file change log to its own file inventory. This log comparison system allows Time Machine to create incremental backups, which usually don’t take long to complete, while keeping a full backup of your files.
Typically, unless you’ve made any major changes or added several new files to your drive, the “backup preparation” process is very quick. In fact, it’s so fast that most Time Machine users never even notice it, except for the first Time Machine backup, where the preparation phase takes a long time.
If you see a very long preparation phase, or if Time Machine seems to be stuck in the preparation process, this guide will help you fix the problem.
Time Machine’s “preparing backups” process takes too long
Check if the preparation process is stuck:
- Start System Preferences by clicking the Dock icon or by choosing System Preferences from the Apple menu .
- To open the Time Machine preferences pane, click its icon in the System area of the System Preferences window .
- You’ll see a “Scanning xxx items,” “Preparing xx items,” or “Preparing backup” message, depending on the version of OS X you’re running.
- The number of message elements should increase, albeit slowly. If the number of items stays the same for more than 30 minutes, then Time Machine is probably stuck. If the number increases or the message changes, then Time Machine is working properly.
- If the number of articles increases, be patient and do not interrupt the preparation phase.
- If you think Time Machine is stuck, give it another 30 minutes, just to be safe.
What to do if the time machine is stuck in the “Backup Preparation” process
- In earlier versions of macOS, you can disable Time Machine by sliding the on/off switch in Time Machine preferences to the Off position . You can also click the Off side of the switch.
Now in macOS Mojave, there is only one checkbox to turn off automatic backups. It’s not clear if this does the same thing as turning Time Machine Off.
Still, the following may be helpful in locating your problem.
- Once Time Machine is turned off, check the following as possible causes of the problem:
If you use any kind of antivirus or malware protection system, make sure the app is set to exclude the volume from Time Machine backups. Some antivirus applications will not 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 you are indexing your Time Machine backup volume. You can prevent Spotlight from indexing your Time Machine backup volume by adding it to the Privacy tab of Spotlight preferences as follows:
- Start System Preferences by clicking the Dock icon or by choosing System Preferences from the Apple menu .
- Open the Reflector preferences pane by clicking its icon in the Personal area of the System Preferences window .
- Click the Privacy tab .
- Drag and drop the 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.
Delete the .inProgress file
Once you prevent Spotlight and any antivirus apps from accessing your Time Machine backup volume, it’s almost time to try again. But first, a bit of manual cleanup.
- With Time Machine still off, open a Finder window and navigate to: /TimeMachineBackupDrive/Backups.backupdb/NameOfBackup/
- This trail needs a bit of an explanation. TimeMachineBackup is the name of the drive you are using to store your backups. In our case, the name of the Time Machine drive is Tardis.
- Backups.backupdb is the folder where Time Machine stores backups. This name never changes.
- Lastly, NameOfBackup is the computer name you assigned to your Mac when you first set up your Mac. If you’ve forgotten the team name, you can find it by opening Sharing preferences; will be displayed at the top. In our case, the computer name is Tom’s iMac. So navigate to /Tardis/Backups.backupdb/Tom’s iMac.
- Inside this folder, look for a file called xxx-xx-xx-xx-xxxxxxxx.inProgress.
- 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.
- The .inProgress file is created by Time Machine as it collects information about the files it needs to back up. You should delete this file if it exists, as it may contain outdated or corrupted information.
- Once the .inProgress file is deleted, you can turn Time Machine back on.
Other Causes of Long Machine Backup Preparation Times
As mentioned above, Time Machine keeps track of files that have been updated and need to be backed up. This file system changelog can become corrupted for a number of reasons, the most likely being an unexpected shutdown or freeze, as well as deleting or shutting down external volumes without properly ejecting them first.
When Time Machine determines that the filesystem changelog is unusable, it performs a deep filesystem scan to build a new changelog. The deep scan process greatly extends the time it takes to prepare Time Machine for a backup. Fortunately, once the deep scan is complete and the changelog has been fixed, Time Machine should perform subsequent backups as normal.
