How to install OS 10.15 on External Drive?

I have an External 1TB Drive formatted as Mac OS Extended Journaled.

I want to install 10.15 on this External Drive (contacted using a SATA to USB drive enclosure).

The Apple Support's Install Instructions state to use 1 of 3 versions of Command-R.

As I want to install the latest version of macOS from the internet (10.15, in my case), I believe I should use "Press and hold Option-Command-R until a spinning globe appears, then release the keys".

How do I select the External Drive as the destination?

I have not tried this completely because it appears to want to do the Install on the Internal Drive.

Thank you, in advance, for your time ans assistance.

Mac mini, macOS 10.15

Posted on Feb 10, 2023 2:36 PM

Top-ranking reply

D.I. Johnson

Level 8

36,627 points

Posted on Feb 10, 2023 2:43 PM

macOS 10.15 Catalina must be installed on a drive that is formatted with APFS and a GUID partition map.

Launch Disk Utility to accomplish that.

Please see: File system formats available in Disk Utility on Mac - Apple Support

When done, download the Catalina installer and launch it, selecting the newly partitioned external drive and follow the prompts.

Please see: How to download macOS - Apple Support

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How to install OS 10.15 on External Drive?

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