Many Mac users who, when a new operating system is launched, want to keep the previous version on their computer for a trial period that allows them to check how the new one responds with their usual applications.

Well, to have both operating systems on your Mac at the same time and allow a dual boot, you don’t need too many requirements. In this article we are going to explain how to configure your Mac so that you can start two versions of macOS.

Why set up a macOS dual boot

There are a number of reasons why you might want to run two versions of the Mac operating system, which is essentially what dual-booting means.

  • When you want to update your Mac to software newer, but you have legacy apps that we might run on the new one. Creating a dual boot could be a solution to test those applications in the new environment.
  • If you are a developer of software and you need to test your own apps on different versions of macOS.
  • When you want to try a beta version of the Mac operating system without compromising or risking that it may cause problems with the applications and data you have on your Mac.

Before going into detail, we must clarify one aspect of dual boot on Mac. In previous versions of macOS X and macOS, it would have been necessary to partition the Mac. In newer versions, the operating system creates a volume automatically.

In this article, we are going to assume that you are running a newer version of macOS, so we will focus on creating a second volume for installation.

First steps

Before taking any step, you must bear in mind the following:

Make some space. If you want to split your Mac so that you can run two versions of the operating system, you will need space. Kill the apps you don’t use, remove the files and folders you don’t need, and copy your photo library to an external drive.

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The next step will be to make a backup. It is always advisable when you are going to perform a task like this, as a prevention that something could go wrong. Query How to Backup a Mac in Simple Steps.

You must be prepared to erase everything. If you are on an older version of macOS when you partition your Mac, you will need to erase it completely. If you want to keep your work, you must create a backup of your Mac, so that the drive can be partitioned.

There are alternatives in this regard, such as the possibility of install the macOS version on a hard drive or external drive, following the complete tutorial.

How to create a new volume on your Mac

The method of creating a dual boot will depend on the version of macOS that you are already running. If you have macOS High Sierra on an SSD, or you have Mojave or Catalina installed, this process is much easier because your Mac will use the Apple APFS file system.

APFS replaced the old file system: HFS +. In this way, APFS has a series of advantages, one of which is the shared use of space, which makes it possible to share the available space between the different volumes of your disk.

It is the way to have more space at any time, and basically, to forget what is assigned to each partition.

If you are using APFS, you can create an APFS volume as we will show you below, and then simply install the new version of the operating system on that volume. You will not need to reformat anything. It couldn’t be easier.

If on the contrary, you are using an older version of macOS, or even Mac OS X, it is a bit more complicated, but we will also see that process in the article.

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How to create an APFS volume

  1. Make a backup of your Mac (because it is always advisable to do so before doing a task like this).
  2. Open ‘Disk Utility’ (you can find it in the ‘Utilities’ folder under ‘Applications’, or just press ‘Command + Space’ to start typing ‘Disk Utility’).
  3. Click on the drop-down menu next to the ‘View’ button on the toolbar and choose ‘Show all devices’. This will ensure that you can see the volumes within your disk. You probably have one called Home.
  4. Select the Startup volume and click the ‘+’ button to create a new volume.
  5. Now, you will need to give your volume a name. If you are testing a new Beta version of the operating system, this could be the word to recognize it better.
  6. You can set the storage limit if you want (although it is not necessary). To set a limit, click on ‘Size Options’ and fill in the minimum storage quota options.
  7. Now click ‘Add’ to add the new volume to your Mac.

Once your second volume is up and running, you are ready to install the new beta or operating system version of macOS.

macOS add APFS volume

If you are using an older version of the Mac operating system and you do not have APFS, you will have to go through a somewhat more complicated process that involves creating a partition. Let’s see how to do it next.

How to install macOS Big Sur on an APFS volume

During the days when macOS Big Sur was in beta, all you had to do was sign up for the ‘Apple beta software program‘and follow the installation instructions. It is something similar to what we have experienced recently with macOS Monterey.

Now that the final version has been released, when the installer window opens and you are asked to choose where to install it, click ‘Show all disks’ to select the new volume.

macOS dual boot

Once the new version has been installed, you can shut down your Mac to force the computer to show you the dual boot menu. Here there may be two modes depending on whether your Mac is one of the new ones with an M1 chip, or you have one with an Intel processor.

  • Mac Apple Silicon M1: Turn on your Mac and press and hold the power button until you see the boot options window, displaying a gear icon labeled ‘Options’. Select and click ‘Continue’.
  • Intel Mac: Make sure your Mac has an Internet connection. Turn on the computer and hold down the ‘Command + R’ keys until you see the Apple logo.
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If you are asked to select a user whose password you know, select it, click ‘next’ and enter the administrator password.

How to install a second macOS system on a partition

If your Mac computer is somewhat older and you have not yet reached the APFS world, you will have to divide the main hard drive into two separate drives and then install macOS Catalina on one partition, and the other version of macOS on the other.

  1. Start macOS in ‘Recovery Mode’ (turn on your Mac and hold down the ‘Command and R’ keys until you see an Apple logo or spinning globe).
  2. Once in recovery mode, use ‘Disk Utility’ to clean the main hard drive and divide it into two partitions.
  3. Now recover your ‘Time Machine’ backup on that partition. Remember, you will not be able to recover a backup based on a newer version of macOS than the one you want to use on this partition.
  4. Alternatively, you can use the ‘Install in Recovery’ option to install the version of macOS you want to run on the main partition.
  5. Now is the time to install the other version of macOS on partition 2. Follow the steps to install a second version of macOS, or the beta version of the new version of macOS, on the second partition.

Finally, we leave you a link to an article in which we explain how to recover a Mac with startup problems. You may also be interested in knowing how to reinstall macOS if recovery mode doesn’t work.

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