How do I create a Catalina USB boot drive from my M1 Mac to repair a corrupted Intel based Mac?

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Level 1

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How do I create a Catalina USB boot drive from my M1 Mac to repair a corrupted Intel based Mac?

I have an older MacBook Pro with Catalina installed. I'm trying to set it up for my son, but I've run into a problem. During my attempt to do a fresh install of the OS, the machine became stuck in a continuous reboot loop. Using command-R, I can get to the repair drive, but I can't seem to make it past that point. If I try to do the fresh install, I receive the message "The target volume is part of incomplete system and can not be installed to." If I try to repair or erase that drive, it immediately fails due to a file being in use. i've read that the way around this is to boot from USB, but that seems to be another roadblock.

Now I'm trying to download the Catalina image from my current M1 based MacBook, and I cannot find a way to do so. The option to download is not selectable due to the incompatibility with the M1 chip, and the old machine that is compatible is, as best I can tell, incapable of downloading such an image until its repaired using the image (the famed Catch 22).

Does anyone have any suggestions on how to resolve this?

Posted on Feb 27, 2022 9:56 AM

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Answer 1

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HWTech

Level 9

60,302 points

Feb 28, 2022 7:13 PM in response to stubadubb

You cannot download macOS Catalina using an M1 Mac, because the M1 Macs shipped with Big Sur from the factory. Apple does not allow people to download an OS from the App Store which is not compatible with the Mac you are booted from. Very annoying, but it is Apple's way.

Try booting into Internet Recovery Mode using Command + Option + R to see if you can boot to the online macOS installer which in theory should be the most recent version of macOS which is compatible with that Mac, although sometimes it will only boot to the online installer for the OS which originally shipped on the Mac from the factory (or 10.7 if the Mac shipped with Snow Leopard). You can also boot to the oldest online macOS installer compatible with your Mac by booting into Internet Recovery Mode using Command + Option + Shift + R. Once you have an OS installed, then you can download the OS of your choice and create a bootable macOS USB installer (or upgrade like normal if you installed the original OS from the factory):

How to create a bootable installer for macOS - Apple Support

When erasing the drive make sure to erase the whole physical drive instead of just the "Macintosh HD" volume (or erase the "Fusion Drive" item if the Mac contains a Fusion Drive setup). With macOS 10.13+ you may need to click "View" within Disk Utility and select "Show All Devices" so that the physical drive appears on the left pane of Disk Utility.

In the future you can download the macOS installer of your choice and archive it from the Applications folder into a read-only .dmg file which you can store on external media. As long as you have access to the download OS installer, you should be able to use your M1 Mac to create a bootable macOS USB installer from the mounted .dmg archive (you will need to modify the path locations slightly unless you temporarily move the archived installer into the Applications folder on the M1 Mac).

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Answer 2

stubadubb Author

Level 1

5 points

Mar 3, 2022 11:35 AM in response to HWTech

Thanks, I appreciate you taking the time to reply with help. I thought I was going to type "thanks, but I've already tried these things, and they didn't work." But, somehow, in spite of my certainty that I did exactly what you laid out, this time when I tried, it worked. I'm not sure what i did differently this time, but I'll take it.

Thanks again!

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