How to install MacOS

I've just replaced the original 1TB HD with a 2TB SDD drive in a Late 2009 iMac 27 inch. Essentially I now have a blank HD so I'd like to know how to install the MacOS ? I did the startup holding down Command-R but of course just got a Folder icon with flashing '?' as there has never been an OS on the drive.

I have access to a MacBook Pro & DVD drive so I could make a boot disk if this was the right course of action but I'd need step-by-step instructions if this is the best course of action

Posted on Dec 20, 2020 10:05 AM

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3 replies

Niel

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Dec 20, 2020 10:17 AM in response to paultuc

Insert a compatible Mac OS X install DVD or connect an installation thumbdrive, and restart with the Option key held down. For that iMac model, the OS on it can't be newer than High Sierra.

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Niel

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Dec 21, 2020 6:17 AM in response to paultuc

Click here and follow the instructions.

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paultuc Author

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Dec 20, 2020 12:42 PM in response to Niel

Thanks - I guess my follow on Q is how do I create an installation thumbdrive? Is there a site I can download the installation SW and how to transfer it to thumbdrive - Just copy it across or do I need to install it in some way?

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How to install MacOS