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macrumors regular
Original poster
Oct 30, 2018
I recently installed Catalina 10.15 and updated to 10.15.1.
As I am facing a couple of issues, I would like to do a clean installation.
To do this, I bought a 64GB USB-C drive (one I used in the past to go to Mojave) and downloaded a copy of Catalina through the AppStore.

After using Diskmaker (the version which is working with Catalina), I rebooted my laptop and hit the OPTION key.

Strangely, the laptop is only showing the main HDD and not the USB stick.
When I log into MacOS, I do see that the USB is recognised and showing Catalina.

Is there a different way to install macOS Catalina?


macrumors regular
Oct 6, 2019
Central New York
If your computer has a T2 chip for security, it will not allow you to use an external drive for a boot disk unless you change a setting. I don't have one so this is from memory of something I read. You boot into recovery mode and there should be a choice for security settings. One of the choices is to allow boot from an external drive.
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