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I'm trying to install Catalina on an external hard drive to use on a 2013 iMac

I've downloaded the Catalina install file, but it won't work on my 2019 iMac running Ventura. what should I try next?

iMac 27″, macOS 10.15

Posted on Jan 26, 2023 2:05 PM

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VikingOSX

Community+ 2024

Level 10

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Posted on Jan 26, 2023 2:21 PM

Get yourself a USB 3.x 16 GB USB stick and then make yourself a bootable installer from that Catalina installer in your Applications folder. Use Disk Utility to format your external drive as APFS. Quit Disk Utility.

See Create a bootable installer for macOS - Apple Support using the Terminal commands for Catalina. When that USB stick is done, reboot your IMac with that external drive connected, and press the option key to present the USB Stick Install macOS Catalina as a selectable device and then select the external drive as the installation target.

After you have installed Catalina on that external drive, leave it connected, reboot your iMac with the option key again, and select that external drive to boot from. Once booted in Catalina, apply anything from Software Update.

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I'm trying to install Catalina on an external hard drive to use on a 2013 iMac

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