whapweasel

macrumors newbie
Original poster
Mar 14, 2018
5
0
England
I have a 27” iMac with a 500gb SSD hard drive. The hard drive is APFS formatted and has a container with 2 volumes OS Majove and OS High Sierra.

Majove is the start up disk.

I would like to erase High Sierra and replace it with Catalina.

When I try to erase High Sierra using disk utility the process fails because High Sierra is mounted and can’t be unmounted because it is in use.

Is this a container/APFS issue ? Why is it in use ?

Thank you
 

dsemf

macrumors 6502
Jul 26, 2014
410
91
I have a 27” iMac with a 500gb SSD hard drive. The hard drive is APFS formatted and has a container with 2 volumes OS Majove and OS High Sierra.

Majove is the start up disk.

I would like to erase High Sierra and replace it with Catalina.

When I try to erase High Sierra using disk utility the process fails because High Sierra is mounted and can’t be unmounted because it is in use.

Is this a container/APFS issue ? Why is it in use ?

Thank you
My guess is that the Mojave system or some application found files that it uses on the High Sierra volume.

If you boot into recovery mode, you should be able to remove the volume. The risk is that whatever was using the volume will now have issues.

DS
 
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whapweasel

macrumors newbie
Original poster
Mar 14, 2018
5
0
England
Thanks for the response.

You are right the volume can't be unmounted as it is in use process 0 (kernel)

What is process 0 and will stopping process 0 by erasing High Sierra be likely to cause any significant issues ?
 
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dsemf

macrumors 6502
Jul 26, 2014
410
91
Thanks for the response.

You are right the volume can't be unmounted as it is in use process 0 (kernel)

What is process 0 and will stopping process 0 by erasing High Sierra be likely to cause any significant issues ?

Process 0 starts with the boot process and ends after shutdown.

If the High Sierra volume is deleted, the results will be unpredictable. Mojave may depend on something being available or it just mounts the High Sierra volume in case it is needed.

If you boot the High Sierra system and enable File Vault, any attempt by Mojave to mount the encrypted High Sierra volume will require authorization. If you cancel the request, you can see if Mojave is impacted by the lack of the High Sierra volume. If everything is OK, you can then use Disk Utility to remove the High Sierra volume since it will not be mounted.

DS
 
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whapweasel

macrumors newbie
Original poster
Mar 14, 2018
5
0
England
I have carried out the procedure which went very smoothly, High Sierra is now unmounted.
I have not found any issues with Mojave.
DS thank you for your help, you are a genius!
 
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smokerz

macrumors newbie
Feb 29, 2008
13
2
Detroit
I have a 27” iMac with a 500gb SSD hard drive. The hard drive is APFS formatted and has a container with 2 volumes OS Majove and OS High Sierra.

Majove is the start up disk.

I would like to erase High Sierra and replace it with Catalina.

When I try to erase High Sierra using disk utility the process fails because High Sierra is mounted and can’t be unmounted because it is in use.

Is this a container/APFS issue ? Why is it in use ?

Thank you
Next time since you would be booted in Mojave just select the - button. then select + button for your Catalina volume. That's the idea behind APFS is never to partition being 'old school' and use a container to add or delete volumes. Each volume shares the total size of the media itself.
 
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MacDuggy

macrumors member
Dec 14, 2019
38
8
When I tried to restore my Catalina OS to a 1TB SSD from the native HDD on a 2012 MacBook Pro the disk utilities drop down menu didn’t list APFS as a choice. I used a third party partioning program on a Windows pc to convert MBR to GUID on the SSD. When I remounted the SSD on the Pro APFS was listed as a choice on disk utilities. The rest of the restore and changing out of the MacBook Pros incumbent HDD for the SSD went smoothly. Difference in boot up speed like night and day.
[automerge]1576450896[/automerge]
... all the while wondering why “disk utilities” a native Apple/Mac program would not do the MBR to GUID conversion?????
 
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