How to update my iMac to macOS Monterey solely running on External HDD?

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How to update my iMac to macOS Monterey solely running on External HDD?

Recently, my iMac's internal HDD died and I brought it in to verify with the Genius tech. I was recommended to just run the OS off of an SSD since it fits my usage needs and extends the life of the device (2015 iMac 5K if i remember correctly off the top of my head). I managed to plug the SSD in, format it, and install OS X on it just fine and it boots perfectly fine. However, I decided I want to run it on Monterey since thats the last version its compatible with... I downloaded Monterey through the app store, it starts to do its thing to update but it ends up loading forever and it is in this loop of installing, and then starts to flash the Question Mark Folder again. I reboot while holding Option and it says OS Installer, I try it again, same thing and it just goes in this cycle. Whereas when I install OS X, it will install and actually be able to show the SSD as a bootable drive instead of cycling as OS Installer.

Sorry if this makes no sense but I wonder if there is any way I can update this to Monterey? (Running the OS solely off of the external SSD)

[Re-Titled By Moderator]

iMac 27″, macOS 10.14

Posted on Jun 3, 2024 9:09 PM

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Answer 1

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BDAqua

Level 10

251,409 points

Jun 3, 2024 9:22 PM in response to H3U6A9

Are you certain you gave it enough time, the installtion may restart itself upto 7 times, & sometimes appears nothing is going on.

Have you run Disk Utility's Disk First Aid on all connected drives?

Start up from macOS Recovery

Option-⌘-R

Upgrade to the latest macOS compatible with your Mac.

In Disk Utility>View, select Show all Devices, highlight the top left entry.

Run Disk First Aid on all items in the left panel, from top down.

Install again.

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Answer 2

Owl-53

Level 10

112,405 points

Jun 5, 2024 2:39 AM in response to H3U6A9

Check the format of your storage device

A Mac startup disk requires either of these file system formats. You can use Disk Utility to select your storage device and see which format it's using. You can also use Disk Utility to erase it using either format.

APFS format is recommended for macOS High Sierra or later, especially if your storage device is a solid-state drive (SSD).
Mac OS Extended (Journaled) format, also known as HFS+, is also acceptable for traditional hard drives, and it's required for macOS Sierra or earlier.

Change your Mac startup disk

If none of the above works after testing

Refer back to posting by @BDAqua

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Answer 3

Owl-53

Level 10

112,405 points

Jun 4, 2024 1:21 AM in response to H3U6A9

Two cents here and not good news.

Back around Monterey 12.3, Apple implemented some EFI Boot ROM inside Monterey

During the Initial Installation, the EFI Boot ROM was assigned by Apple to check if the Destination Drive was an Apple Original Drive

Should it not find an Original Drive - the installation process would fail.

Background - the EFI Boot ROM, being part of the Monterey Installer, needs to Flash the Computers Boot ROM.

It does not touch the Drive itself

Once that condition is achieved, applying a new Boot ROM to the computer, the installation of Monterey would continue

As the " iMac's internal HDD died " not sure what the solution might be outside of trying another Apple Original SSD in a Enclosure

www.owc.com maybe a good starting point ?

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Answer 4

BDAqua

Level 10

251,409 points

Jun 3, 2024 9:37 PM in response to H3U6A9

It sound like you eed to reformat the drive, do you have backups?

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Answer 5

H3U6A9 Author

Level 1

4 points

Jun 3, 2024 9:26 PM in response to BDAqua

I am certain! I know it can restart a few times but eventually it restarts and then boots into the flashing question mark folder. Which then I’m forced to reboot and hold option but it says OS installer (instead of the name of the drive like it says when I install OS X)

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Answer 6

H3U6A9 Author

Level 1

4 points

Jun 4, 2024 9:34 AM in response to Owl-53

So I did manage to get the update to go through. However, the only issue now is that it won’t boot straight into the SSD without me holding Option and selecting the SSD manually. Once it loads, if I don’t log in it’ll eventually go to sleep or something and go back to the flashing question mark folder.

Id then reboot, option, manually select and it will load up and run seemingly fine. I’ve already made sure the start up disk is selected to the SSD but idk why it’s not?

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How to update my iMac to macOS Monterey solely running on External HDD?

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