How to fix partition issues with Boot Camp on macOS

Installing Windows on Mac via Boot Camp is usually a straight forward process. Apple has created a Boot Camp Assistant app in macOS that guides users through the complete process. Even though the steps are simple, sometimes Boot Camp gives an odd error with disk partitions that is confusing to figure out. Here is how you can easily fix it.

Fixing Boot Camp startup disk issue

The issue usually occurs if Windows installation fails and Boot Camp Assistant is unable to restore the partitions in their original state. If you get the below message, you know you’re facing this same issue:

The startup disk cannot be partitioned or restored to a single partition. 

The startup disk must be formatted as as single Mac OS Extended (Journaled) volume or already partitioned by Boot Camp Assistant for installing Windows.

Boot Camp Assistant

This issue can happen due to either of the following reasons:

  • FileVault – you can disable it from System Preferences > Security & Privacy
  • Time Machine – this can be disabled from System Preferences > Time Machine
  • Failed Windows installation via Boot Camp Assistant

In either of these issues, you will have to remove the partition and retry installation. Your first reaction might be to delete the new Boot Camp partition so that you can restart the installation process. However, when you go to Disk Utility to try and delete the Boot Camp partition, you will notice that the (-) isn’t active anymore. You get the below message:

You can not remove this volume because the previous volume can not be resized.

Disk Utility

While this seems kind of an odd situation to be in, the solution is pretty simple. You do not need to open up Terminal and use Diskutil, just follow these steps:

  • In Disk Utility, you will notice that there is an 8 GB partition next to the Boot Camp volume. This volume is called OSXRESERVED. Select it, and click the minus button.
  • Once it’s removed, click on the BOOTCAMP volume and you will see that the minus button is active again. Click it to remove the volume.

You should now be able to restart Windows installation using Boot Camp Assistant.

P.S. OSXRESERVED is created just for the Boot Camp installation process and is removed by macOS after Windows is installed. If, somehow, you still see it after installing Windows, you can follow the above steps to remove it and recover 8 GB storage space.