Files inaccessible after Mojave downgrade

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Level 1

8 points

Files inaccessible after Mojave downgrade

Hi all,

I have recently successfully downgraded from Catalina to Mojave (to use software for old camcorder video capture) and created a new volume to run Catalina for other stuff. I have a backup of all needed files so there's no issue with losing stuff.

My problem is this: I did not know that when downgrading to Mojave, all the hard drive's contents would remain there taking up storage space but be inaccessible at the same time. So now with my 2 volumes I have 260 odd GB of "used space" that I can't access or delete. If I load all my stuff back on the Catalina volume, I'll have used up over 500GB of my 1TB drive and won't have as much space for the camcorder videos as I would have liked.

Was there a better way I could've handled this? Is there anything I can do now to clear that space?

Thanks in advance for any advice or comments.

AlitaJJ

iMac 21.5", macOS 10.15

Posted on Mar 2, 2020 2:43 PM

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Answer 1

Top-ranking reply

leroydouglas

Community+ 2024

Level 10

188,712 points

Mar 3, 2020 5:02 AM in response to AlitaJJ

AlitaJJ wrote:

Hi all,

I have recently successfully downgraded from Catalina to Mojave (to use software for old camcorder video capture) and created a new volume to run Catalina for other stuff. I have a backup of all needed files so there's no issue with losing stuff.

My problem is this: I did not know that when downgrading to Mojave, all the hard drive's contents would remain there taking up storage space but be inaccessible at the same time. So now with my 2 volumes I have 260 odd GB of "used space" that I can't access or delete. If I load all my stuff back on the Catalina volume, I'll have used up over 500GB of my 1TB drive and won't have as much space for the camcorder videos as I would have liked.

Was there a better way I could've handled this? Is there anything I can do now to clear that space?

Thanks in advance for any advice or comments.

AlitaJJ

It is a little unclear to undestand exactly the complexity of your issue is here—

one problem arise from an incomplete erase/format of the internal drive when reverting back to Mojave.

Revert your Mac to a previous macOS version - Apple Support

Disk Utility>View>Show All Devices here you see the "Parent" drive. It is this Parent drive that needs to be erase/format. That is to say—reformat at the drive level, not the Container & volume level (child).

From the Terminal.app copy and paste:

diskutil list internal

This will give a better look & understanding if you post it here for discussion:

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Answer 2

AlitaJJ Author

Level 1

8 points

Mar 3, 2020 4:08 PM in response to leroydouglas

Thanks Leroy, I appreciate your response. Thanks for the links and info regarding parent drive. Just FYI I have a 2015 Mac that was originally shipped with High Sierra. Please excuse the long story below, yes the situation is complicated!

I'll attach a screenshot of what I'm talking about. But yes, I think you are right - I did not wipe the hard drive before reverting to Mojave. I chose not to use my time machine for Mojave revert because the last time I used it we had four User logins, too many files and junk and the Mac was suffering RAM problems/peaks that were freezing the computer. Apple shop wiped the drive in November and did a clean install which I upgraded to Catalina and carried on as normal. However, recently I hit a huge snag when I discovered iMovie no longer supports old camcorder video capture, and the software I needed was not supported by Catalina - that is how I ended up in this mess!! I have 70 hours of home video to capture so I needed a solution. I used a USB stick with bootable Mojave to install over Catalina. I was under the impression that doing this would overwrite my old data, obviously I was wrong..

Here are some shots of my now somewhat 'busy' Parent Drive..The light grey lined area is empty but 'reserved' for my Catalina volume.

Where it says "Used space" above - that is the problem. Its about 270GB and is all my data from when I was running Catalina just before the revert to Mojave.

Below is my parent drive highlighted.

Below is my new volume with Catalina installed and only a few files.

Below is my Mojave revert which was installed where I was previously using Catalina.

Now, before I go too far with loading up all my files and capturing videos, should I wipe the parent drive and begin again building my dual-boot system? Perhaps this is the only way to move forward with more space..I would appreciate any advice or opinions you could give me.

thanks

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Answer 3

dwb

Level 7

33,100 points

Mar 4, 2020 10:26 AM in response to AlitaJJ

'Reverting' means you've removed the former OS, totally erased the drive, and started over. You didn't do that because it the past it was easy to erase the drive and start over. Not any longer. Catalina creates a container for two parts of Catalina - CatalinaOS and Catalina Data. Actually they aren't named quite correctly. CatalinaOS is indeed the operating system and it is read only. Catalina Data contains a small amount of OS that needs to be modified, applications, and data.

So, you need to reboot into the Recovery partition, delete both the Catalina and Mojave containers, and then reformat. Then you can restore using your Mojave backup

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Answer 4

AlitaJJ Author

Level 1

8 points

Mar 4, 2020 6:20 PM in response to dwb

Thank you DWB :) You have also solved my question. Your explanation of Catalina being in 2 parts now, and exactly in which order to do things to fix the problem is much appreciated. I will start over now .. and hopefully end up with a clean, empty drive ready to reload files!

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Files inaccessible after Mojave downgrade

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