A Fix for Time Machine's Backup Failure

Posted by Aaron West at 1:30 PM in Mac, Leopard

Returning home from the Adobe Community Summit I knew there were a couple of things I had to do. Getting a bit of rest and hanging out with my wife and son were at the very top of the list. Closer to the bottom was plugging my MBP into a power brick in order to backup my computer to my Time Capsule. Little did I know it wasn't going to be as easy as usual.

After plugging in and initiating the backup, Time Machine took over 20 minutes to prepare the data - it simply displayed "Preparing data" for what seemed like ages. Finally, it finished the prepare data phase and displayed how much data it was backing up, about 5.3 GB. I'm simply amazed that one weeks worth of work could generate 5.3 GB of changed data. Realizing it was going to take Time Machine quite a while to copy 5.3 GB wirelessly to the Time Capsule I shut the MBP's screen about 80% of the way and decided to return to the living room to do other things.

A few hours later I came back to my MBP to see the following message:

First, many thanks to Apple for giving me a useful error message I could do something about. Pfff. I tried several things to get Time Machine working again including rebooting, reconnecting to the Time Capsule, and simply restarting the backup process. All failed with the same error message.

After hitting up Google for answers (Google always seems to have answers you know) I found a few posts on the MacCast forums that seemed promising. A user by the name of "karinlord" deserves credit for the right set of steps to mitigate this problem.

I believe my problem started when my computer decided to sleep in the middle of the backup process. I am unsure if this occurred because of my systems preferences or whether I actually shut the computer lid enough to force it to sleep. Regardless, Time Machine seems to freak out if it gets interrupted during the backup process. When this happens several files and folders are left on your backup volume that deter any subsequent backups.

To get Time Machine going again, you need to remove the errant files with the following steps:

  1. Ensure your backup device is turned on and connected to your computer (wirelessly or wired, it doesn't matter)
  2. Turn off Time Machine using the big button in Time Machine preferences. NOTE: I did not execute this step and was still able to fix Time Machine.
  3. Make sure the backup volume (which is just part of the backup drive) is mounted to your desktop/Finder. You may have to initiate (and subsequently cancel) a Time Machine backup process in order to see the drive on the desktop or in Finder.
  4. Access your backup volume in Finder (it should be named "Backup of your-computer-name..." or something similar) and double-click into the "Backups.backupdb" folder.
  5. Next, click into the "your-computer-name" folder. You should see a bunch of folders with dates. These are all the dates corresponding to days you ran a successful backup.
  6. At the bottom of the folder listing will be one or two things you need to move to the trash. You may see only one or both of these, but delete the file that starts with a date (it should be the date the backup failure started) and ends in ".inProgress." Also delete a file named "Latest" if it exists.
  7. Return to Time Machine preferences and turn Time Machine on. Remember, I was successful without performing this step.
  8. Initiate a backup using the Time Machine drop-down in the menu bar or wait until the next scheduled backup run.
  9. A final but important step, be patient. Time Machine may sit in "preparing" mode for a while. It's important to at least let it run for an hour or so to see if the process will continue actually writing files to your backup volume.

If you continue having problems and are unable to get Time Machine to perform a successful backup, I recommend running the following command in Terminal. This command will let you view your system log - where Time Machine errors are located - in order to [possibly] get a clearer picture of what is causing your backups to fail.

sudo grep backupd /var/log/system.log


Day three of the Adobe Community Summit was the second day of talks by various folks at Adobe. The day was jam packed with more content and information than presented the previous day. Read on for more...

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