(Monterey) How do I wipe out a whole physical drive completely?

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coxorange Author

Level 2

151 points

(Monterey) How do I wipe out a whole physical drive completely?

Hello,

In my case it's the remaining 120GB SSD of a late 2015 iMac's Fusion Drive (where the HDD failed).

When it happened I was using Monterey on that Mac,

then it only let me install El Capitan (which came with that Mac).

In the end I want to install Monterey again on the SSD.

At the moment when I try to install Monterey direct from an USB installer it gets stuck in a loop (progress bar always restarting at about 24%).

Internet recovery (alt+cmd+R) takes me to the Monterey recovery screen.

"Reinstall macOS Monterey" didn't work, I guess because the SSD was not completely empty.

Maybe I could use Terminal?

This is how Disk Utility shows the SSD:

Thank you.

[Edited by Moderator]

iMac 27″, OS X 10.11

Posted on Aug 29, 2025 03:47 PM

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Answer 1

Top-ranking reply

HWTech

Level 9

66,674 points

Aug 30, 2025 12:56 PM in response to coxorange

It appears you have a broken Fusion Drive probably due to a failing Hard Drive.

Unfortunately to recreate a Fusion Drive involves destroying all data on both drives which I don't advise because the Hard Drive most likely has a physical failure.

If you want to install macOS to the 120GB internal SSD, then you will need to erase the whole physical SSD. Select the "Apple SSD SM0128G Media" as GUID partition & MacOS Extended (Journaled).

A 120GB SSD will only allow you to have a very limited macOS experience since you won't be able to install too many apps or have too much data stored on the internal SSD (You need to keep at least 20GB+ of Free storage space at all times).

A better option is to install macOS to an external USB3 SSD and boot & use the computer from the external SSD.

FYI, the "Base System" is just a virtual volume from the macOS installer.....ignore it and any other virtual volumes.

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Answer 2

coxorange Author

Level 2

151 points

Aug 30, 2025 03:12 AM in response to coxorange

OK, I guess a Disk Image with "Base System" is always installed when a disk (here SSD) is erased, correct?

I will try now to "Reinstall macOS Monterey" (2nd option in the recovery screen) on the SSD...

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Answer 3

coxorange Author

Level 2

151 points

Aug 30, 2025 03:39 AM in response to coxorange

No, this didn't work!

The installation started, but after a while it failed and displayed a blinking white folder with a "?" on it.

When I boot (cmd+R), it offers me the El Capitan recovery screen, which I don't want.

When I boot (cmd+alt+R), it offers me the Monterey recovery screen.

I now repeat "Reinstall macOS Monterey" (2nd option in the recovery screen)...

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Answer 4

coxorange Author

Level 2

151 points

Aug 31, 2025 03:04 AM in response to HWTech

Thanks for your answer!

Yes the hard drive has a physical failure.

If you want to install macOS to the 120GB internal SSD, then you will need to erase the whole physical SSD. Select the "Apple SSD SM0128G Media" as GUID partition & MacOS Extended (Journaled).

Did it and then, via internet recovery (cmd+R), I was able to install El Captain again, which confirms that the SSD is healthy.

But I wanted to install Monterey on the SSD, and this is where I struggle.

Internet recovery (cmd+alt+R) offers me to install Monterey (last supported macOS for that Mac), but I get in that installation loop...

It seems something isn't quite prepared for that installation...

Can you imagine what is missing?

Thank you.

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Answer 5

HWTech

Level 9

66,674 points

Aug 31, 2025 05:08 PM in response to coxorange

Why don't you download the Monterey installer & run it while booted into El Capitan?

How to download and install macOS - Apple Support

Theoretically you should be able to use the Software Update option in macOS to do it as well. I don't recall where this option is located on El Capitan, perhaps an icon on the System Preferences?

coxorange wrote:

Did it and then, via internet recovery (cmd+R), I was able to install El Captain again, which confirms that the SSD is healthy.

Not necessarily....it only means the SSD was working well enough at that moment to finish installing El Capitan.

But I wanted to install Monterey on the SSD, and this is where I struggle.

Internet recovery (cmd+alt+R) offers me to install Monterey (last supported macOS for that Mac), but I get in that installation loop...

It seems something isn't quite prepared for that installation...

Can you imagine what is missing?

No, because there are no details about how far the install process gets.

Does it ever finish the downloading/copying of installer files to the SSD (aka Phase #1)?

Does it complete Phase #1 and reboot? You should see an Apple logo & progress bar on a black screen IIRC.

How far does the progress bar get in a specific phase?

Any error messages?

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Answer 6

coxorange Author

Level 2

151 points

Sep 3, 2025 02:30 AM in response to HWTech

Thanks for your answer, here is what I did:

I searched for "macOS Monterey" in Safari and found a link to the Mac App Store (which is not shown when you search direct in MAS). From there I downloaded the installer and ran it while in El Capitan (as you suggested). Again it was stuck in the "About 29 minutes remaining..." loop.

Then I tried a new WD 4TB external USB3-drive (formatted Mac OS Extended, Journaled) and ran the downloaded Monterey installer. It began installing on that drive, but then it was the same stuck-in-the-loop result !

Then I tried to install High Sierra on the external drive. It installed perfectly!

I tried Mojave on that drive. Perfect. (Though it seems that such a "normal" mechanical HDD is very slow for that purpose. And the installation took a lot of time and was very noisy...)

Then I tried the same on the internal SSD. To make it short:

High Sierra √

Mojave √

Catalina √

Big Sur √

Monterey √ (mission accomplished)

And now I remember I had an issue years ago when I tried to upgrade from Catalina to Monterey on an other Mac. It was not possible before upgrading to Big Sur.

So the secret was to just do single upgrades, one by one, even if that takes a lot of time.

Thanks again for your help.

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