Update your software

Time Machine is unable to complete a backup, make note of any alert message that appears. You can also open System Preferences and in Time Machine preferences click the red "i" icon for more information.

Messages you may see after clicking the red "i" include:

"The backup volume is read only."

"No volumes to be backed up were available."

"Unable to complete backup. An error occured while copying files to the backup volume."

"The backup volume could not be mounted." or "The backup volume could not be found."

"Time Machine could not be configured..."

Update your software

Regardless of the specific issue, you should first make sure your software is up-to-date.

If you use Time Machine with Time Capsule, make sure you have updated your Time Capsule with the latest available software and firmware.

Message: "Preparing" phase takes a long time

Time Machine keeps track of files and folders that have changed since your last backup so that it only backs up those files and folders. If Time Machine loses track of files and folders that have changed since the last backup, it compares an "inventory" of your current data to an inventory of your backup. When this happens, Time Machine preferences displays a "Preparing..." status message for a longer period of time. See Mac OS X 10.5: Time Machine preferences may display "Preparing" for a longer time.

Message: Time Machine starts a new, full backup instead of a smaller incremental backup

There are three reasons why this may occur:

You performed a full restore.

Your Computer Name (in Sharing preferences) was changed--when this happens, Time Machine will perform a full backup on its next scheduled backup time.

If you have had a hardware repair recently, contact the Apple Authorized Service Provider or Apple Retail Store that performed your repair. In the meantime, you can still browse and recover previous backups by right-clicking or Control-clicking the Time Machine Dock icon, and choosing "Browse Other Time Machine disks" from the contextual menu.

Message: Some items are not backed up

If Time Machine does not back up a particular file, you may have marked it "Do not back up" in Time Machine preferences.

To remove files from the "Do not back up" list:

Choose System Preferences from the Apple menu.

From the View menu, choose Time Machine.

Click Options.

Look in the "Do not back up" list. To remove an item that should not be in the list, select it and click Remove (-).

Click Done.

In rare situations, Time Machine may be unable to back up third-party software (software from companies other than Apple), due to a setting made by that software manufacturer. For more information, contact the vendor of the software.

Message: "The disk (volume name) was not repairable by this computer. it is being made available to you with limited functionality. You must back up your data and reformat the disk as soon as possible."

Attempt to repair your Time Machine's backup:

Choose System

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