MacBook Air running Big Sur.
Want to install Mojave on separately created partition, as Big Sur is not compatible with program.
Have created APFS partition.
Have downloaded Mojave as a .dmg
How do I create a bootable USB drive to install Mojave on the created partition? (I assume it has to be done that way?)
Thanks guys for any help!
Happy New Year
MacBook Air 13″, macOS 10.15
If this Mac shipped with Catalina, you will not be able to install Mojave. You can't boot directly to an OS older than what the Mac shipped with.
If you need Mojave, your only choice on that Mac is to run a virtual machine, such as VMware, Parallels or VirtualBox. You can then install the older OS in the VM.
You need a bare minimum of 8 GB of RAM for this. 16 or more preferable since you'll be running an OS within an OS.
If this Mac shipped with Catalina, you will not be able to install Mojave. You can't boot directly to an OS older than what the Mac shipped with.
If you need Mojave, your only choice on that Mac is to run a virtual machine, such as VMware, Parallels or VirtualBox. You can then install the older OS in the VM.
You need a bare minimum of 8 GB of RAM for this. 16 or more preferable since you'll be running an OS within an OS.
The full installer app for Mojave downloads to your Applications folder as
Install macOS Mojave.app (6.05GBs), any .dmg is probably not the full installer.
Get it here, use your Safari browser, not any others
How to get old versions of macOS – Apple Support
Go to Download OS and click on macOS Mojave
this will redirect you to the App Store Mojave download page
it should say Get or Download.
You may find as you are running Big Sur it mat refuse the download,
try Control-clicking on Get.
How did you create the partition, can you share a screenshot of Disk Utility
and your Disk and Volume tree.
okay, hit a snag.
When I boot from bootable USB containing install package the partition I created for the older OS does not appear as an option to install to.
I get the usual reinstall Big Sur option, connect to safari etc, but no way to pick the separate partition (it doesn't even show)
Is it not possible to 'go backwards'?
thanks again for any help.
I'm wondering why one of your Macintosh HDs is not mounted.
When you created the partitions did you do it from the Disk and not the indented Volumes.
For example If you started with Big Sur on the disk unpartitioned then to make
the next partition you should highlight the Disk click on Partition and then in
the next window make and size your partitions, each new partition should
once created should appear under its own Container Disk.
When you boot to the USB click on Install OS the installation
should start up in in the following windows you will be asked
to select the Volume/ disk you want to install the OS to.
old OS on separate APFS partition
