Fix Time Machine When Stuck on “Preparing Backup” in Mac OS X

Time Machine is by far the simplest way to keep regular and reliable backups of a Mac, and usually the automatic backups start and finish without any incident. On some rare occasions though, Time Machine may get stuck* on the “Preparing Backup” stage for an inordinately long amount of time, causing a backup to never start, let alone finish. It’s these failed backup attempts that we’re looking to remedy here.

We should point out that if you haven’t backed up a Mac in a while, say a few months, it’s normal for the “Preparing Backup” stage of Time Machine to take a while to gather data before beginning, particularly if you have a large drive to backup. What’s not normal is for the Preparing Backup stage to take 12-24 hours, getting stuck in that stage overnight or all day long, for example (unless perhaps you have some truly absurd amount of disk space, then it may take that long and be normal).

Anyway, having consistent and reliable backups is important, so lets fix this specific Time Machine issue in OS X.

How to Fix a Stuck “Preparing Backup” Issue in Time Machine for Mac

We’ll go through a multi-step troubleshooting process to resolve the preparing backup problem and get Time Machine working in Mac OS X again.

Let’s begin:

Stop the Currently Failing Backup Attempt Before Beginning

The first thing you need to do is cease the currently failed backup attempt while it is stuck on “preparing backup”, this is easy enough:

• Open the “Time Machine” settings panel within System Preferences (get there from the  Apple menu or Time machine menu)
• Click the little (x) icon until the backup attempt stops

When the progress bar disappears and it no longer says “Preparing backup…” you’re good to begin the troubleshooting process outlined below.

1: Trash the “inProgress” File

Now that the backup is stopped, the first thing to do is trash the Time Machine placeholder file found on the backup drive:

1. Open the Time Machine drive in the Finder and navigate to the “Backups.backupd” folder
2. Open the folder within Backups.backupd that is the name of the current Mac which is stuck on preparing
3. Put this directory into “List View” and sort by ‘Date Modified’, or just search the folder for a file with a “.inProgress” file extension
4. Delete the “xxxx-xx-xx-xxxxxx.inProgress” file

The .inProgress file is always in the form of xxxx-xx-xx-xxxxxx.inProgress, where the first 8 digits are the year-month-day (date) and the next 6 or so digits are random numbers, followed by the inProgress file extension.

Just trash that file, it should be about 3kb or so.

2: Reboot with the Time Machine Drive Connected

Next, give the Mac a good old fashioned reboot while the Time Machine drive is connected to the Mac, you’ll see why that matters in a moment:

1. Pull down the  Apple menu and and choose “Restart”
2. Once booted, let Spotlight run completely (you can either just wait it out or watch the mdworker, mrs, and related processes in Activity Monitor)

This should cause OS X to re-index the attached Time Machine drive if it’s needed, which may be getting in the way of Time Machine backing up properly thus causing the computer to get stuck on “Preparing Backup” for a very long time. Even if the drive has been recently indexed by Spotlight, a reboot still appears to be necessary, whether to resolve whatever issues are occurring with backupd or not.

3: Initiate a Backup as Usual

Now that the Mac has rebooted with the Time Machine drive connected, you can start a back up yourself. The easiest way to do this is through the Time Machine menu icon or the System Preferences:

• Pull down the Time Machine icon and choose “Back Up Now”

You will still see a “Preparing backup…” message but it should be gone within a few minutes, depending on the size of the hard drive, the speed of the Mac, and the size of the backup to be made. At this point, your Time Machine backup will proceed as expected, so just let it run and you’re good to go again.

* For those who like to get technical, when “preparing backup” gets stuck, the actual ‘backupd’ process is usually doing nothing at all, with no disk activity or CPU usage shown from Activity Monitor, fs_usage, and opensnoop. Admittedly a bit advanced, but those tools show a definitive way to demonstrate this specific issue and resolution.