Want to clean install macOS High Sierra but unable to delete the existing Macintosh HD partition. An internal error has occurred.

[codegix]

Hello everyone, I have an iMac 18,2 with the current operating macOS Sierra. Now I want to clean install the existing OS using macOS High Sierra v10.13.6, I went to the recovery mode, connect to wifi and click on Reinstall but the issue that I encountered is whenever I try to install it I get the following error:

An error occurred while preparing the installation. Try running this application again (I tried this more than 5 times and still get the same error).

An error occurred while preparing the installation. Try running this application again (I tried this more than 5 times and still get the same error).


I spent a couple of hours trying to find a solution and one of them said that I need to delete the Macintosh partition or check on the partition disk for error first. So, I went ahead and clicked First Aid scan the disk for error for the Macintosh HD partition but it also failed with an internal error. When I try to delete the partition and always get the following error message:

Erasing "Macintosh HD" and Creating "Macintosh HD"

Erase process has failed. Click Done to continue.

When I click show Details:

Erasing APFS Volume File Content

An internal error has occurred.

Operation failed

Is there a way to completely remove the partition, and do a clean install? I also was not able to unmount the partition.

I was also able to create a USB installer for this and the MacOS Sierra can still be used without issue. Is there a complete step on how can I resolve this issue of being unable to erase the partition? My aim is to be able to install MacOS High Sierra in clean mode. I don't want any backups left. Thank you...

PS: this imac originally came with MacOS High Sierra but it was mistakenly downgraded to Sieera

 

[Fishrrman]

"I was also able to create a USB installer for this and the MacOS Sierra can still be used without issue. Is there a complete step on how can I resolve this issue of being unable to erase the partition? My aim is to be able to install MacOS High Sierra in clean mode. I don't want any backups left."

My reply is based upon the premise that you don't care about anything that's on the drive NOW. It will be wiped out.

You can't use "the recovery partition" to install High Sierra, because you can't erase the ENTIRE DRIVE from the recovery partition.

Having said that, you probably can't install High Sierra using internet recovery either.
REASON WHY:
Internet recovery (command-OPTION-R) will offer you the most recent OS that will run on a 2017 iMac.

The special version of internet recovery (command-SHIFT-OPTION-R) will offer you "Low Sierra" (OS 10.12), because that's what the 2017 iMacs originally shipped with.

So... my guess is the ONLY WAY you can install High Sierra (OS 10.13) is by using a bootable USB flash drive (which you say that you already have).
NOTE: you could TRY the special version of internet recovery to see whether it offers you Low Sierra or High Sierra...

So... do this:
1. Boot from the USB flashdrive. Press the power on button and then IMMEDIATELY hold down the OPTION key and KEEP HOLDING IT DOWN.
2. The startup manager will appear.
3. Select the USB drive with the pointer and hit return.
4. The Mac should boot from the flashdrive
5. It will probably boot to the OS installer. DO NOT RUN IT YET. Hit "command-Q" to quit.
6. Now you should see the utilities menu. Open DISK UTILITY
7. VERY IMPORTANT: in disk utility, go to the view menu and choose "show ALL devices". DO NOT SKIP this step!
8. Now, look at "the list on the left". The "topmost" item should be the physical drive inside.
9. Click on the drive and then click "erase".
10. Erase to "Mac OS extended, journaling enabled, GUID partition format"
11. Once the erase is done, quit disk utility and RE-OPEN the OS installer
12. Start clicking through. The Mac will reboot one or more times, and the screen will go dark for a minute or more with no other indication of activity. Just be patient.
13. When done, you should see the initial setup screen (choose your language).
14. At this point you can either set it up completely fresh, or connect a backup drive and use setup assistant to migrate data.

Good luck.

 

[codegix]

"I was also able to create a USB installer for this and the MacOS Sierra can still be used without issue. Is there a complete step on how can I resolve this issue of being unable to erase the partition? My aim is to be able to install MacOS High Sierra in clean mode. I don't want any backups left."

My reply is based upon the premise that you don't care about anything that's on the drive NOW. It will be wiped out.

You can't use "the recovery partition" to install High Sierra, because you can't erase the ENTIRE DRIVE from the recovery partition.

Having said that, you probably can't install High Sierra using internet recovery either.
REASON WHY:
Internet recovery (command-OPTION-R) will offer you the most recent OS that will run on a 2017 iMac.

The special version of internet recovery (command-SHIFT-OPTION-R) will offer you "Low Sierra" (OS 10.12), because that's what the 2017 iMacs originally shipped with.

So... my guess is the ONLY WAY you can install High Sierra (OS 10.13) is by using a bootable USB flash drive (which you say that you already have).
NOTE: you could TRY the special version of internet recovery to see whether it offers you Low Sierra or High Sierra...

So... do this:
1. Boot from the USB flashdrive. Press the power on button and then IMMEDIATELY hold down the OPTION key and KEEP HOLDING IT DOWN.
2. The startup manager will appear.
3. Select the USB drive with the pointer and hit return.
4. The Mac should boot from the flashdrive
5. It will probably boot to the OS installer. DO NOT RUN IT YET. Hit "command-Q" to quit.
6. Now you should see the utilities menu. Open DISK UTILITY
7. VERY IMPORTANT: in disk utility, go to the view menu and choose "show ALL devices". DO NOT SKIP this step!
8. Now, look at "the list on the left". The "topmost" item should be the physical drive inside.
9. Click on the drive and then click "erase".
10. Erase to "Mac OS extended, journaling enabled, GUID partition format"
11. Once the erase is done, quit disk utility and RE-OPEN the OS installer
12. Start clicking through. The Mac will reboot one or more times, and the screen will go dark for a minute or more with no other indication of activity. Just be patient.
13. When done, you should see the initial setup screen (choose your language).
14. At this point you can either set it up completely fresh, or connect a backup drive and use setup assistant to migrate data.

Good luck.

Thank you so much.. i will try this and let you know the result.

 

[MBAir2010]

Yesterday I had to erase a real nice OCLP Monterey and Catalina partitioned SSD drive formatted in APFS
so I can use Mojave Mac journal for an older version of creative suite on a MacBook Pro 2012
and [B]Fishrrman[/B]'s steps are very accurate and solid!

now I need to reformat another APFS drive that was in a Mac mini to Mac journal
so I can back up the MacBook Pro via Time Machine.
I might just plop that into an enclosure and erase-reformat on an MacBook Air 2010.

fun fun!