How to Fix Time Machine Backup Failures and Errors

For Mac OS X users, Time Machine is not strange. It is a backup software application that keeps a copy of all your files, and allows you to restore the whole system or specific files whenever you need. Recently, however, we found that many users are discussing on forums about Time Machine backup error and failure. Are you wondering why Time Machine failed to backup? This article contains answers to many common issues about Time Machine backup and troubleshoots to alert messages while time machine could not complete the backup.

Troubleshooting-Time Machine Failed to Complete Backup


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Solution to First Backup Failure

If this is your first backup, or the first time to a new external drive/partition, the most common cause might be that the drive has not been formatted properly. Follow the steps to set up using Disk Utility.

  • Open Disk Utility in Applications>Utilities folder.
  • Select Startup drive, it usually names Macintosh HD on the second line of the side bar. On the bottom you will see detailed information of this HD.
  • In Format it is Mac OS Extended (Journaled).
  • mac hd format
  • Select the line for your external drive that you set up to backup files. If you are not sure, please check in Time Machine Preferences.
  • The format of this drive should be the same as your Startup drive. If they are not the same, you need to erase the partition and select the format to the same as Startup drive.

If Time Machine is still unable to complete a backup, please note the alert message it sends. If you missed it, you can open Time Machine preferences, and click the red "I" icon for more info.

alert message from time machine

Solutions to Specific Alert Messages When Time Machine Failed to Complete the Backup

Regardless of what warning message it appears, firstly you should make sure your software is up-to-date.

Messages you may receive while Time Machine failing to complete a backup:

Message 1: The backup volume is read only

  • Turn Time Machine Off: Launch System Preferences >Time Machine, move the slider to OFF.
  • If your backups are on an external HD, please eject the drive from your computer and disconnect it for a while. And then restart the Mac to connect the drive again.

Message 2: Time Machine could not complete the backup.

The entire alert message like this:

cannot complete backup

Usually this problem can be resolved after you restart the Mac. If this does not help, please format your external HDD and create a new partition for your backups.

Message 3: An error occurred while copying files.

backup failed

This message occurs for no specific reason. Restart and then try the backup once again should fix it.

Message 4: The backup disk is almost full

When the backup is disk full and lock of enough space, the Time Machine will delete old backups to make room for new ones. If you are not willing to remove old backups, please open Time Machine preferences to set up a new backup disk.

backup disk is full

Message 5: No volumes to be backed up were available.

Open System Preferences, in Time Machine preferences pane, click Options. Please check and confirm you have not excluded all available volumes.


We wish you can fix the Time Machine backup issues disturbing you. If the problems you are having do not include here, write on the comment and we will respond as soon as we can. If you lose files on Mac, the Mac Data Recovery aims to help you recover deleted files.

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