How to update iMac 14,2 to the latest supported macOS?

I have a very old iMac 14,2 It has OS X Mountain Lion. I want to update it to the latest OS it can run. It will not connect to Software Update. It is on the internet, I can ping OK.

How do I do this?


[Re-Titled by Moderator]

Posted on Jan 11, 2025 09:18 AM

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3 replies

Jan 11, 2025 07:26 PM in response to dagny gromer

iMac14,2 is an iMac (27-inch, Late 2013).


Mountain Lion is so old that its version of Safari might not be able to access modern https links – like the one for the Apple Support article. Possibly its versions of the App Store and Software Update are outdated as well.


Workaround:

  • Back up your old iMac.
  • Use a modern Mac or PC to download the .DMG file containing the El Capitan installer, or the Sierra installer, and to put this .DMG onto a USB drive. This will NOT create a bootable drive; just one with a .DMG data file on it.
  • Copy the .DMG file from the USB drive to the old iMac.
  • Open the .DMG file / mount the image, and run the installer application inside.


If the installation succeeds, this will get you to an operating system recent enough that its versions of Safari and of the App Store might let you access the Support article from the old iMac to finish upgrading the rest of the way.


Note that Catalina breaks 32-bit applications, and splits up the functions of iTunes among several applications. But Catalina is recent enough to run current versions of the Firefox Web browser, and of LibreOffice.

Jan 12, 2025 09:35 AM in response to dagny gromer

Thanks to all who responded.

I had to do a series of updates, it was not possible to jump right to Catalina which is the last supported OS for this device. To make this project even more "fun", Safari on Mountain Lion could not even connect to apple.com due to the newer https protocols.

I found non-https (plain old http) site http://maclinks.publicvm.com which had downloads for older OS's accessible by old browsers. A good resource! I had to install El Capitan then High Sierra manually, then I could use the OS update feature to progress. At one time I lost my wifi credentials in an update, no big deal of course when I realized that's why I had no internet connectivity.

This took much of a day to complete.

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How to update iMac 14,2 to the latest supported macOS?

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