A lot of Mac admins need to test software in their environment against both the shipping version of macOS and older versions of OS X. However, getting older OS installers from the Mac App Store (MAS) can be problematic if the Mac you’re using isn’t able to run the older OS as its own operating system. If the Mac you’re using isn’t itself able to run the older OS, a request to download the OS installer from the MAS will result in an error message like the one shown below.
If you’re in this situation, but also have VMware Fusion or a similar virtualization solution available, there is a way to download the desired older OS installer using a VM running the shipping version of macOS. For more details, see below the jump.
The method described below uses VMware Fusion, but should be replicable using any virtualization solution which supports running the shipping version of macOS as a guest OS.
1. If needed, create a new VM running the shipping version of macOS.
2. Log into the VM.
3. Launch the App Store application and sign in with the desired Apple ID.
4. Select the desired OS installer and click the Download button.
5. You’ll receive a message that a newer version of the OS is installed and are asked to confirm that you want to download the older OS installer. Click the Continue button.
6. The older OS installer should download.
7. Once the installer has completed downloading, copy it out of the VM to a convenient location.
