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Creating a dual boot environment is an ideal solution for Mac users who want to install and try macOS Sierra but without interfering with their primary stable Mac OS X El Capitan installation. This tutorial will walk through the entire process of setting up such an environment, including partition a disk, and installing macOS Sierra 10.12 beta onto that partition to allow for a dual boot.


The process of creating a dual boot Mac OS environment is not particularly difficult but it involves some risk and setup steps which could result in catastrophic data loss, thus this is generally aimed at advanced users and is not appropriate for novices. Completing a full system backup beforehand is essential.

While we’re focusing on installing MacOS Sierra onto a partition for dual boot purposes, you can also install macOS Sierra onto an external hard drive, a USB drive, or even an SD card, and have the same dual boot situation between the macOS Sierra beta and the OS X El Capitan stable release, though performance is usually not as good when an operating system is running off an external volume.

Requirements for Dual Booting MacOS Sierra Beta & OS X EL Capitan:

  • Back up the Mac before beginning, you can learn how to set up Time Machine backups if you have not done so already
  • Be sure the Mac supports MacOS Sierra, refer to this MacOS Sierra compatibility list to be certain the Mac can run 10.12
  • The MacOS Sierra installer app downloaded from Apple, or as a bootable Sierra installer drive
  • Sufficient hard disk space on the Mac to allow for a new partition to be created to run MacOS Sierra from (assume 20GB or more for Sierra partition, and allow at least 10GB of storage on the primary Mac OS X installation as well)
  • If it is a Mac laptop, connect to a power source before beginning

Be sure you have backed up your Mac before beginning this process. You will be partitioning a hard drive and then installing beta system software. Failure to adequately backup your Mac and your data may result in permanent data loss, do not skip a backup.

How to Create a MacOS Sierra Partition

You will need to partition the hard drive of the Mac to add a new partition for which to install Mac OS Sierra onto. This allows MacOS Sierra to run in a self-contained installation without impacting your primary stable OS X EL Capitan installation, thus allowing the dual boot. Here’s how to add a partition:

    1. Open Disk Utility, the app is found in /Applications/Utilities/
Disk Utility icon
    1. Choose your hard drive from the left menu list
Select the partition button in Disk Utility
    1. Click the “Partition” button, then click the [+] plus button to create a new partition
    2. Name the new partition something very obvious like “Sierra”, and then assign the partition a reasonable amount of space (20GB minimum or more is a good idea for basic testing)
Add new partition
    1. Choose “Apply” to finish and to create the new partition on the drive
Apply the partition change

Quit out of Disk Utility when finished, you’re now ready to install MacOS Sierra on the new partition.

How to Install MacOS Sierra to the New Partition

Assuming you backed up, partitioned the Mac, and have macOS Sierra downloaded, you can now safely install MacOS Sierra 10.12 onto the separate partition, this will allow you to preserve your existing OS X installation without potentially messing it up with the new beta system software.

    1. Launch the MacOS Sierra Installer from the /Applications/ folder on the Mac, it is currently labeled as “Install 10.12 Developer Preview.app”
Install MacOS Sierra
    1. Go through the installer as usual, when you get to the disk selection screen, choose “Show All Disks” and choose “Sierra” from the list, then click on “Install” to begin installing MacOS Sierra onto that partition
Choose show all disks in MacOS Sierra installer
    1. Let the installation run its course, the Mac will reboot to complete the job, and when finished the computer will automatically boot into macOS Sierra when installation is complete
Select the partition to install macOS Sierra onto

Now you’re in macOS Sierra running off the separate partition, this gives you access to files on your Mac but preserves the other stable operating system, in this case OS X El Capita. For what it’s worth, this would work the same with OS X Yosemite and Mavericks too if you’re wanting to dual boot Sierra with those releases as well.

MacOS Sierra desktop screenshot

Dual Booting and Switching Between MacOS Sierra 10.12 and OS X El Capitan

You can now easily dual boot between MacOS Sierra and the other stable Mac OS X release. This is quite simple, if you want to switch between the operating systems, all you do is:

  1. Reboot the Mac from the  Apple menu as usual
  2. Hold down the OPTION key when you hear the boot chime sound
  3. Select the drive and operating system you want to boot from and use, whether MacOS Sierra or OS X El Capitan

It’s that simple, you can reboot and switch between the operating systems running on the same Mac with ease.

If you ever want to get rid of one of the operating systems, or remove the MacOS Sierra beta partition, just go back into Disk Utility and delete the partition you wish to remove. Keep in mind that if you delete a partition, you also delete all data and files on that partition.

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Founder and Chief Editor of Colabyte, Jitendra Malviya likes to keep on top of technology and loves to help people around him get through the day to day trouble they face with technology. So that, they can love technology as much as he does!

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