Configure Time Machine To Use a New Hard Drive

Do you need to reconfigure Time Machine to use a new external hard drive? If you read my Tech Tips regularly then you’ll recall that I strongly recommend that everybody setup automatic and redundant systems to backup his or her Mac. If you use Time Machine to backup your Mac to an external hard drive then you either have or will replace the external drive when it dies. Here are instructions on how to reconfigure Time Machine to use a different hard drive.

  • Click on the Apple menu and select System Preferences
  • Click on Time Machine
  • Click the Select Disk button. [Note: If your Mac is configured to backup to 2 or more backup drives then the button will be labeled Add/Remove Backup Disk.]
  • In the Backup Disks section, click on the name of the external hard drive that has died and then click the Remove Disk button.
  • In the Available Disks section, click on the name of the external hard drive that is replacing the dead hard drive then click the Use Disk button.
  • You should see a prompt asking if you want to replace your current drive or if you want to use both drives. In this case, you want to replace it.   [Important: Since most new hard drives come setup (formatted) as PC hard drives. Time Machine may inform you that it needs to erase (reformat) this hard drive so it can be used as a Mac hard drive. If you see this prompt, let this occur.]
  • Click the red dot to close System Preferences.
  • Within a couple of minutes, Time Machine will initiate a backup to this new hard drive. Let this backup run in the background. It’ll likely take many hours to finish since it needs to backup everything on your Mac.


  1. Thanks for this. I often wonder why Apple doesn’t give such clear and simple instructions on its support pages. I was prompted to encrypt the drive. I did that and now I’m sorry. Do you have instructions on removing a password (yes, I know pw) from a TM backup drive? 🙂

    • Hi Maura,
      Apple provides simple instructions that cover how to initially setup Time Machine and restore files from it. For whatever reason, they don’t happen to provide instructions on how to replace an USB external hard drive when it fails. Thus, I wrote some instructions and I’m sure other people have as well.

      The password that you set on your USB external hard drive is used to encrypt the data that gets stored on that drive. To the best of my knowledge, the only way to remove the password is to erase your USB external hard drive. You could use Disk Utility to erase it which would, of course, delete all of existing backup data stored on this drive. Then you could configure Time Machine to backup to this recently erased USB external hard drive. This Apple Support page provides some instructions on using Disk Utility. Note that you should select which version of the Mac operating system (macOS) you have on your Mac so you get macOS-specific instructions.

Leave a Reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.