Install the new macOS Catalina without having to forego Mojave (or High Sierra)? That sounds absurd at first, but it isn't at all. Because you can install both operating systems in parallel on your hard drive on your Apple Mac and use them with their respective advantages (and disadvantages). This is conceivable if you deal professionally with macOS 10.15 Catalina, but not the many Problems and Limitations want to accept. Even if you want to continue to use 32-bit apps under macOS 10.14 Mojave, you can install Catalina in parallel with Mojave without a partition. Here I'll show you how to do it.
Chapter in this post:
The pioneer: APFS file system
The Apple File System (APFS) is responsible for making parallel installation and alternating use of two operating systems on the Mac entirely possible. And in a very simple way. It is no longer necessary to create a new partition and reserve it for the second system. There is also no need to move to a second hard drive or external data carrier. You can find some more information about APFS in this guide. The following is now about the instructions with which you can install macOS Catalina without a partition parallel to Mojave or High Sierra.
Instructions: Use two macOS versions without a partition on one hard drive
Apple makes it really easy for one to accomplish this feat under APFS. Basically, all you have to do is create a new volume (a kind of virtual hard drive) and install Catalina on it. But there are one or two small hurdles. So that you don't trip over it, here are the instructions:
- Opens Disk Utility (via Launchpad or Spotlight)
- Make sure your hard drive is operating in the APFS file system
- If this is the case, click on the "+" above the word "Volume"
- You will now be asked for the name and format of the new volume
- You can freely assign the name ("Catalina" is a good idea); you leave APFS as the format
This creates the basis for the double installation of operating systems on your Mac. But when you try to install Catalina next to Mojave, you may not see the new volume. Don't worry, this is normal. This is how you do it:
- Start the macOS Catalina installer from your hard drive (that's how you get it)
- The note where the OS will be installed now shows the regular hard drive (Macintosh HD)
- You select your new "Catalina" volume by clicking on "Show all volumes ..." below
- In addition to the Macintosh HD, the hard disk space created with the above steps is now displayed
- Select this and complete the installation
Choose a startup disk and switch between Mojave and Catalina
Now you want to determine or at least check which volume the Mac boots from when it starts. To do this, simply open the system settings ( -> System settings ...) and then select the item "Startup volume". In the window that opens, you can now specify which system should be loaded when the Mac starts.
If you want to change this directly at start-up and use the other system, then stop immediately after switching on the computer Option key (option, old or ⌥) pressed. This will take you to the start volume selection. Unfortunately, you cannot simply switch between the two systems during operation. Here a restart of the computer is necessary before or during which you switch to the other system using the options shown.
Partitions are now unnecessary and are no longer recommended
It is not only possible with APFS to install two operating systems in parallel on a hard drive on an Apple Mac. That was already possible before. However, a so-called “partition” had to be defined for this. That was depending on the procedure (Portcommand, tools with a clear user interface, etc.) sometimes complicated, sometimes simpler. But those times are over with APFS – so basically with macOS 10.13 High Sierra.
Apple itself no longer recommends partitions under the current file system, as described in the support document HT208891 emerges. Partitions, the required size of which is not automatically determined and must be specified by the user, are used for the file system Mac OS Extended recommended. You can find the note at the bottom under the heading "Further information".
Jens has been running the blog since 2012. He acts as Sir Apfelot for his readers and helps them with technical problems. In his spare time he rides electric unicycles, takes photos (preferably with the iPhone, of course), climbs around in the Hessian mountains or hikes with the family. His articles deal with Apple products, news from the world of drones or solutions to current bugs.