How to Deal with the “Disk Cannot Be Partitioned” Error?

Apple’s transition to Intel processors has made it possible to install Windows on Macs thereby benefiting from having two OSs on the same computer. The allure of switching to Windows is reinforced by the ease with which it can be done. In fact, the majority of Macs supports the latest Microsoft OS — Windows 10. Furthermore, Apple computers with OS X 10.5 or later come with Boot Camp Assistant, which is needed to partition a hard drive prior to the installation of Windows.

Unfortunately, when trying to partition their hard drive, some users encounter the following error message: “This disk cannot be partitioned because it is impossible to move some of its files.” This article explains the reason for the error occurrence and provides an effective workaround for the issue.

Why A Boot Camp Partition Can’t Be Created?

When creating a partition for Windows, a user has to dedicate a certain amount of free space on the hard drive. If there is enough available space on the drive to make a reasonably large partition and Boot Camp Assistant refuses to initiate the partitioning process, it means that there is data that occupies the area dedicated for the partition.

The Solution

The solution to the problem is to clone Mac’s drive to an external drive, thereby creating its exact copy, and erase the internal macOS partition after booting from the external drive. The process of cloning can be performed with the help of Disk Utility. Although it has changed with the introduction of OS X El Captain and now involves additional steps, it is still an effective method of making a copy of a startup drive.

Note that for the purpose of creating a bootable drive, it is possible to use hard drives, SSDs, and even USB flash drives. When it comes to the size of a USB flash drive suitable for carrying a bootable copy of macOS, it should be 16 GB or larger.

To install macOS on the drive, start by formatting it with Disk Utility. The formatting standard that has to be selected is Mac OS X Extended. The next step is to enable ownership of the drive. To this end:

  1. Right-click on the icon of the drive;
  2. In a pop-up window, select the Get Info option;
  3. Click on the lock icon to open settings;
  4. Enter the administrator password;
  5. Uncheck the box next to the Ignore ownership on this volume option;

Check the permissions on the Mac’s startup drive in Disk Utility. To do so:

  1. Select the drive in Disk Utility and click on the First Aid tab;
  2. Click on the Repair Disk Permissions

To initiate the cloning process:

  1. Choose the startup disk in Disk Utility and click on the Restore tab;
  2. Drag and drop the disk to the Source field;
  3. Drag and drop the USB flash drive to the Destination field;
  4. Select the Erase Destination option and click on the Restore

What needs to be done next is to:

  1. Hold the Option key when rebooting the Mac;
  2. In the Startup Manager, choose the USB flash drive with the bootable copy of macOS;
  3. Press the Return

Once booted from the flash drive, a user has to erase the internal macOS partition by using Disk Utility. Once the process is finished, it is necessary to use a third-party cloning utility to transfer macOS back to the internal drive. After all operations described in the article are successfully performed, it should be possible to create a Windows partition.