What To Do if you See ‘Your disk could not be partitioned’

Are you trying to partition your hard drive to install Windows using Boot Camp on a Mac? Can’t get it done manually with Disk Utility either? You’re not alone. It is a common problem that many Mac users have experienced. Fortunately, the error is fairly straightforward to address. If you see ‘Your disk could not be partitioned’ in Boot Camp, this is how to fix it.

Running multiple operating systems on a single machine is a great way to play around with other OS, use OS-specific programs and experiment without having to buy a different computer. I have a Windows machine that runs Hackintosh and a Mac that runs Windows 10 in Bootcamp. I get to experiment with each OS and can simulate errors my computer repair clients experience so I can fix their problems faster.

Boot Camp

Once Mac became Intel-based, the option to boot multiple operating systems became a reality. The same processor architecture meant that the differences between Mac OS X and Windows could be emulated in software, making each accessible to the other even though they work completely differently.

Boot Camp is Apple’s program that enables you to dual boot your Mac with Windows. It creates a separate partition and a bootloader that will prompt you to select an operating system when you hold down the Option key as you boot your Mac. Most of the time it works seamlessly, sometimes it does throw up an error like ‘Your disk could not be partitioned’.

Your disk could not be partitioned

The only times I have seen ‘Your disk could not be partitioned’ errors have been on older Macs that have been in use for a while. I have not seen it on newer Macs or recently unboxed ones. This leads me to believe that the message is caused by some kind of error in the file system. It seems serious enough to prevent partitioning but not serious enough to affect normal operation.

Whatever the cause, the fix is fairly straightforward. There are two stages to this fix. The first step will address the error in many situations. If it doesn’t fix it for you, try the second. Backup your Mac as appropriate in case anything bad happens. Then:

1. Launch Disk Utility from Utilities.
2. Select your drive from the left and select Verify Disk.
3. Allow the disk to be checked for errors and select Repair Disk if the utility finds any.
4. Reboot and retry Boot Camp.

If the verification finds no errors or fixes them but you still see ‘Your disk could not be partitioned’, try the next fix.

1. Shut down your Mac.
2. Turn it on again and hold down Command + S to access Single User Mode.
3. Open a command prompt, type ‘/sbin/fsck-fy’ and hit Enter. Allow the process to complete.
4. Type ‘reboot’ and hit Enter.
5. Run Disk Utility again and allow the process to complete.
6. Retry Boot Camp.

This second step is also an error check but on a deeper level. If that first fix doesn’t work this definitely should.

Using Boot Camp to dual boot with Windows

If you want to dual boot Mac OS X with Windows, you can use the built-in Boot Camp to partition your drive ready for the install. You will need a legit copy of Windows to install but the rest is all contained within OS X. Here is how to set up Windows on a Mac.

1. Navigate to Utilities and select Boot Camp Assistant.
2. Select Continue within the Assistant and select ‘Download the Windows support software for this Mac’ if prompted.
3. Select Continue and enter your Apple ID if prompted.
4. Select Enter to download and install everything you’ll need.
5. Adjust the slider to size your new Windows partition when prompted to by the Boot Camp Assistant. Windows will need at least 20Gb to work well.
6. Select Partition to get things going.
7. Install your Windows installation media once Boot Camp Assistant has completed the partition.
8. Select Start Installation and your Mac will do just that. There may be a couple of reboots as part of the process.
9. Select Custom installation when prompted and select the BOOTCAMP partition.
10. Select Drive options and then Format to prepare the partition for Windows.
11. Follow the Windows installation wizard as it prompts you for input. Select the settings most appropriate for your needs.
12. Once complete, remove the Windows installation media.

Be very careful at Step 9 to select the correct partition to install Windows on. Make sure to select the partition you created earlier otherwise you may overwrite your MAC OS X installation. When I did it, Boot Camp Assistant named it BOOTCAMP. Yours may differ so choose carefully when it comes to selecting the correct partition.

When you load Windows, it should update the drivers and itself as it would on a normal Windows computer. Now all you need do is hold down the Option key when you boot to access the boot loader to choose which OS to load!