Nov 15, 2015 I'm attempting to partition a 500gb external HDD to run bootcamp, but whenever I go into Disk Utility, the option to partition the drive is greyed out. I've previously erased and formatted to Mac OS X Journaled, so there's nothing on it, but still the partition option isn't available (see screenshot). Any help is majorly appreciated. Winclone 6.0 - MAC OS X ReleaseLoadName: Winclone for Mac. Version: 6.0. Release Date: March 15th 2017. Mac Platform: Intel. OS version:OS X 10.11 or later. Requirements: Windows 7 (64-bit), 8.1, or 10: Winclone allows you to clone your Boot Camp partition. It also includes Windows 7 and 8.1 cloning!

If you've always wanted to partition your Mac's hard drive so you can run a separate operating system — including the launch of macOS Big Sur — in tandem with your current one, it's surprisingly easy to do so thanks to Apple's built-in disk utility program. Here's how to partition your Mac.

What is a disk partition?

Partitioning your Mac is basically splitting your hard drive into separate, usable systems. It makes it possible to run two separate operating systems on one device, like Windows and macOS, or two versions of macOS (like Catalina and Big Sur).

Note: If you want to run Windows on your Mac, Apple's Boot Camp assistant will automatically make a partition for you. Here's how to install Windows.

It is important to note that partitioning your hard drive also splits up your available hard drive space. Each partition will take up a portion of your usable storage. So, if you are running low on storage capacity on your hard drive, we don't recommend partitioning.

Before you start

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The most important thing to do before making any changes to your hard drive is to back it up. Seriously. Back it up. Please. Time Machine is the easiest way to back up your data if you don't already have another system in place.

Second, make sure you have enough free disk space to properly run a secondary operating system. Shoot for at least 30GB free, though I recommend closer to 50GB if you have it available.

How to create a partition on your Mac

1. Open Finder from your dock.

2. Select Applications.

3. Scroll down and open the Utilities folder.

4. Double-click to open Disk Utility.

5. Select your hard drive in the Disk Utility window. It will be the first drive on the list. It might be named 'Fusion,' or 'Macintosh HD.'
6. Click on the Partition tab. You will be prompted to either add an APFS volume or a Partition.

7. Click Partition.

8. Click the Add partition button it looks like a plus (+) symbol.
9. Change the size of the partition you wish to use by dragging the resize controls. The used space is represented in blue.
10. Name the new partition.
11. Specify which file system format you want to use. If you're running macOS 10.13 or higher, you'll want APFS. If you are running macOS 10.12 or older, you'll want Mac OS Extended.

12. Click apply.

Disk Utility will check the disk and make changes. This will take several minutes.

How to switch partitions

You can switch to the new partition, install the current macOS, and then download and install macOS Catalina from there.

1. Click the Apple icon in the upper-left corner of your screen.

2. Select System Preferences from the drop-down menu.

3. Select Startup Disk.

4. Click the Lock in the lower left corner of the window to unlock and make changes.

5. Enter your system admin password.
6. Click OK.
7. Select your partition drive.

8. Click Restart.

You can also restart your Mac and press the Option Key when you hear the startup chime. This will take you to the Startup Manager and you can select your drive from there.

You will then be asked to install macOS. This will install the latest available macOS onto the partitioned hard drive. You may have to install an older version of macOS before updating it to the more recent version you want to run.

If you are testing a beta version of macOS, you'll first install whatever the current version is. Then, you can then install the macOS beta.

How to download the developer beta of macOS Big Sur

Once you've updated your partitioned Mac with macOS Catalina, you can download and install the developer beta of macOS Big Sur. You need a developer account and probably some patience. Developer betas are often a bit complicated to install. We've got a guide to help you out.

Any questions?

Do you have any questions about installing a partition or downloading a new operating system onto a partitioned drive? Let us know in the comments. If you're having trouble partitioning your hard drive, be sure to check out our forums for help!

Updated June 2020: Updated for the developer beta of macOS Big Sur.

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