If Boot Camp Assistant says that your disk could not be partitioned

Boot Camp Assistant might say that an error occurred while partitioning the disk for Windows.

When attempting to create a Windows partition, Boot Camp Assistant might show the alert ”Your disk could not be partitioned. An error occurred while partitioning the disk. Please run First Aid from within Disk Utility to check and fix the error.”

Use Disk Utility to check for errors

  1. Make sure that you've installed the latest macOS updates
  2. Restart your Mac, then press and hold Command-R to start up from macOS Recovery.
  3. Open Disk Utility from the macOS Utilities window.
  4. Choose View > Show All Devices from the menu bar in Disk Utility. The sidebar in Disk Utility should now show more details about your internal disk:
    • The name of your disk, such as Apple SSD
    • The name of a container on that disk, such as Container disk1 (your disk might not have a container)
    • The names of one or more volumes in the container or disk, such as Macintosh HD.
  5. Select the name of a volume, such as Macintosh HD.
  6. Click First Aid in the toolbar. If you're asked for a password to unlock the disk, enter your administrator password.
  7. Click Run to begin checking the volume for errors. When done, repeat for any other volumes in the container or disk.
    Disk Utility window after clicking the First Aid button
  8. If a container is shown, select the name of the container, then use First Aid to check it as well.
  9. Select the name of the disk, such as Apple SSD, then use First Aid to check it as well.
  10. Restart your Mac.

 


If Disk Utility found no errors or repaired all errors

  1. Try again to use Boot Camp Assistant to install Windows.
  2. If Boot Camp Assistant still gives the partitioning error, continue to the steps below.

Check for unallocated free space

  1. Open Disk Utility, which is in the Utilities folder of your Applications folder.
  2. In the Disk Utility sidebar, select the name of your internal disk, container, or volume, such as Macintosh HD.
  3. Click Partition in the toolbar.
  4. If you see a message about Apple File System space sharing, click Partition to confirm that you want to partition instead of add a volume.
  5. If the pie chart shows a section labeled ”Free space,” click to select it. ”Free space” should now also appear in the Partition Information shown on the right.
    Disk Utility window after clicking the Partition button
  6. After selecting the ”Free space” section of the chart, click the remove (–) button beneath the chart. Removing this unallocated free space makes that space available for your use again. Then click Apply and quit Disk Utility.
  7. Try again to use Boot Camp Assistant to install Windows.
  8. If Boot Camp Assistant still gives the same partitioning error, continue to the steps below.

Turn off Time Machine temporarily

If you use Time Machine with macOS Mojave or High Sierra, either upgrade to macOS Catalina 10.5 or later, or follow these steps:

  1. Open Time Machine preferences from the Time Machine menu  in the menu bar. Or choose Apple menu  > System Preferences, then click Time Machine.
  2. Deselect ”Back Up Automatically” to turn off Time Machine. 
  3. Wait a few minutes, then try again to use Boot Camp Assistant to install Windows.
  4. After installation is complete, you can turn on Time Machine again.

 


If Disk Utility found errors that it can't repair

  1. Back up any data that you want to keep, then use Disk Utility to erase (format) your disk from macOS Recovery.
  2. Reinstall macOS from macOS Recovery.
  3. Use Boot Camp Assistant to install Windows.

 


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