Software⏱️ 3 min read📅 2026-06-11

How to Fix: Error during Time Machine backups on OS X Lion

Error during Time Machine backups on OS X Lion - unable to complete backup due to setxattr error for HostUUID key.

Quick Answer: Run Disk Utility again and check if the HostUUID attribute is correctly set. If not, try resetting the System Management Controller (SMC) or Power Management Unit (PMU).

📋 Table of Contents

  1. 🔍 Why This Happens
  2. ✅ Best Solutions to Fix It
  3. 💡 Conclusion

Error during Time Machine backups on OS X Lion can be frustrating, especially when it occurs unexpectedly. If you're experiencing this issue with your internal hard drive being backed up to an external USB hard drive on OS X Lion (10.7), don't worry - we've got a step-by-step guide to help you resolve the problem.

Time Machine is designed to provide reliable backups, but sometimes technical issues can arise. In this troubleshooting guide, we'll walk you through the possible causes and solutions for the 'Unable to complete backup' error during Time Machine backups on OS X Lion.

🔍 Why This Happens

  • The primary cause of this error is a permissions issue with the Time Machine backup folder. The 'com.apple.backupd.HostUUID' key has an incorrect value, which prevents the backup from proceeding. This can occur due to a corrupted or incomplete disk image, or if the external hard drive is not properly formatted.
  • Another possible cause is a problem with the external hard drive's file system. If the file system on the external hard drive is not compatible with Time Machine, it may cause issues during the backup process.

✅ Best Solutions to Fix It

Repairing the Time Machine Partition

  1. Step 1: Step 1: Open Disk Utility and select the external hard drive from the list of available disks. Then, click on the 'First Aid' tab and click the 'Run' button to start the disk repair process.
  2. Step 2: Step 2: Wait for the disk repair process to complete. This may take several minutes, depending on the size of the external hard drive.
  3. Step 3: Step 3: Once the disk repair process is complete, restart your Mac and try running the Time Machine backup again.

Formatting the External Hard Drive

  1. Step 1: Step 1: Connect the external hard drive to your Mac using a USB cable.
  2. Step 2: Step 2: Open Disk Utility and select the external hard drive from the list of available disks. Then, click on the 'Erase' tab and select 'Quick Erase' or 'Security Options' depending on your preference.
  3. Step 3: Step 3: Wait for the external hard drive to be formatted. This may take several minutes, depending on the size of the external hard drive.

💡 Conclusion

If you've tried repairing the Time Machine partition and still experience issues with backups, formatting the external hard drive may be a viable solution. However, if you're not comfortable with this process or prefer a more straightforward approach, repairing the Time Machine partition is usually the recommended fix.

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