My intel iMac is on Sonoma but I want to install Catalina on a partition but it won't.
Create a bootable installer from that Catalina (or straight to Ventura if that is your goal?) installer, Option-boot to it, and install to APFS volume.
Create a bootable installer for macOS - Apple Support
Just curious – Why do you want to install Catalina?
If it's to run 32-bit applications, you want something earlier than Catalina (if your Mac supports something earlier). Catalina is the version of macOS that dropped support for them.
Is that a recent download of Catalina? I remember Apple in the past has date restricted older copies of an installer so you can only install the absolutely newest version of a system.
I have created a bootable external drive but I had to make sure it was Extended Journaled as it wouldn't install on a APFS but then when I option booted to the external drive to do the full Monterey install it tells me the external drive is locked. I don't have an iMac with a T2 Security chip. It does look like it will let me install on a partition of the internal hard drive. Will this cause problems? So my hard drive main system will be Sonoma (might upgrade to Sequoia) then on the partition if it works and doesn't cause problems I will have Monterey so I can install Cinema 4d r20.
Hello, I need to install Cinema 4D on Catalina then update to Ventura as I updated to Sonoma and the menu in Cinema is not working.
Thank you I will give that a go.
The usual method is to create a bootable macOS installer on a thumb drive. As you have noticed it must be erased as MacOS Extended in order for the Terminal command then to succeed.
Then Option-boot to that. Then switch to Disk Utility and create and erase APFS volume either to some other (*) external disk or maybe to the internal disk -- I'd recommend an external disk to avoid messing with the internal unless you know what you re doing.
(*) I'd suspect that you tried to install to that same external macOS installer disk which of course is locked. So make sure to follow the instructions to the letter and be careful when choosing where to install.
Unable to install macOS
