I am trying to create a clean install of OS X Catalina on a USB drive for my '13 iMac using an M1 Air

AFAIK - an M1 MBA will not and can not be used to download or even create a Bootable Installer for anything older than what was originally installed on the computer - that would be Big Sur.

Again - AFAIK - there is no workaround except to preform the download and create the Bootable Installer from a Qualifing computer to run Catalina.

The installer app contains all the code to install on an Intel or M1 mac, there are not two separate

installers.

Which OS is your M1 mac running, if it came preinstalled with Big Sur you will not be able to

download the Catalina installer, if the mac was upgraded from Catalina to Big Sur I think you

will not be allowed to download Catalina either. Big Sur will not allow you to download

older OS installers.

Do you have any other macs you can get access to, macs that you know are capable

of running macOS Catalina if so open your Safari browser and click on this link,

How to create a bootable installer for macOS – Apple Support (UK) Download macOS Catalina via the link provide in the article.

eggMcMark wrote:

I have a '13 Intel iMac, which has a failing HDD, and I have read many blogs and forum posts about creating bootable USB drives, but none I've found address this issue.

I would like to use my brand new M1 Air to create the USB boot drive, and I have gotten far enough to realize that the M1 processors use a different version of Catalina, and I am not able to download the full installer for an Intel Mac using the App Store on my M1 Air. Assuming I found a workaround to get the full intel installer onto the M1 Air, would it be possible to create a bootable startup drive for use on the Intel iMac?

How to reinstall macOS from macOS Recovery - https://support.apple.com/en-us/HT204904

You can't create a bootable flash drive for Catalina from a M1 Mac. P. Phillips answered that with his first post.

However, one can install Catalina on the intel Mac via this method:

1 - boot into the Recovery volume (boot with the Command + R keys held down) on the intel Mac and reinstall the system. It will be the last system that was run on the intel Mac.

2 - if the last system on the intel Mac was before Catalina go to the App Store on the intel Mac, search for Catalan and download the full installer.

3 - launch and run the full Catalina installer on the intel Mac.

I have 2 Macs: 1 M1 MacMini, and 1 Intel MBP. I need to be able to create bootable media for the Intel machine. Are you saying I have to go find someone else with an Intel Mac in order to do this? That's insane!

I can tell you I got the installer onto my M1 MacMini and the createinstallmedia app just dies

% sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/BootCatalina
zsh: killed     sudo  --volume /Volumes/BootCatalina

And of course any web search comes up with zero correct responses because there are too many other articles for creating bootable media for the appropriate architecture.

Hopefully someone has gotten this figured out?

No, I'm not able to get internet access to the Intel MBP until after I install the OS. It's a long story but that's the situation, and it just baffles me this isn't allowed either by the OS or rosetta or something.

Is anyone able to answer the question being asked by me and the OP, rather than suggesting alternatives? This doesn't seem like too much of a corner case.

Actually, my previous response was directed to the OP.

I'm sure your situation is exactly the same and so it's good that you can answer for them.

Rather than drop in on their iMac & MBA problem with confusing commentary, it's probably best that you start a fresh post stating exactly your issues with your Mac mini & MacBookPro and its lack of Internet Recovery so that users can give proper attention to both the OP and you without distraction.

Maybe, rather than drop in on an iMac & MBA problem with confusing alternatives that don't answer the OP's question, maybe let someone else answer it.

His question: "Assuming I found a workaround to get the full intel installer onto the M1 Air, would it be possible to create a bootable startup drive for use on the Intel iMac?"

I have the same question. Although your response may give the OP an alternate solution, I believe the original question is still valid.

what P. Phillips said.

Can you not boot the iMac to Internet Recovery and install the macOS onto the USB drive from there?

User @leroydouglas has posted a link to the support article detailing the process.

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