Downgrading from Catalina to High Sierra – what am I doing wrong?

[Waikiki_61]

Hi everyone,

I wonder if anyone could tell me where I am going wrong in my attempt to downgrade from OS 10.15 (Catalina) to 10.13 (High Sierra).

Computer: Desktop iMac, late 2012, 27-inch.

Objective: To use Photoshop CS6 with a graphics tablet (Adobe CS6 will not work with Catalina).


What I have tried:

Creating a bootable installer on a USB flash drive.
I downloaded the installer for High Sierra, typed in the appropriate command into Terminal (which I am not familiar with at all, just following steps provided elsewhere) and the procedure was successful.
The USB is a Toshiba, 16GB. It is not especially fast but it was the only one I had with the required 14GB of space.

Next I tried to install High Sierra via the USB. Booted up while holding Option. Released it when the screen showed bootable volumes; selected my USB, selected install High Sierra. The installation process did not complete, giving the error message "com.apple.osinstallerror -3"
I tried this three times.

Solutions that I tried after this:

1. Booted while holding Command + Shift + Option + R. The computer started the process to install OS 10.8 (Mountain Lion) but it did not show any clickable Hard Drive icon to install it on.

2. I read that it could work if you revert from APFS file system to the older HFS+ one (again, not something I'm familiar with). There is a command to enter in Terminal, but I had no idea how to use Terminal when using a boot installer on USB.


I'm out of ideas so any suggestions you could give me would be most useful. Also if I haven't clarified anything, please ask.
Thanks very much for reading.

 

[IngoX]

Solutions that I tried after this:

1. Booted while holding Command + Shift + Option + R. The computer started the process to install OS 10.8 (Mountain Lion) but it did not show any clickable Hard Drive icon to install it on.

2. I read that it could work if you revert from APFS file system to the older HFS+ one (again, not something I'm familiar with). There is a command to enter in Terminal, but I had no idea how to use Terminal when using a boot installer on USB.

Instead of Terminal, in Internet Recovery use Disk Utility to revert to HFS+.

You might have to choose View > Show all devices
In the sidebar select the internal disk
Select Erase tab
Select Partition map: GUID, Format: Mac OS Extended
click Erase, then Done

Then return to Reinstall Mac OS

 

[Waikiki_61]

Instead of Terminal, in Internet Recovery use Disk Utility to revert to HFS+.

You might have to choose View > Show all devices
In the sidebar select the internal disk
Select Erase tab
Select Partition map: GUID, Format: Mac OS Extended
click Erase, then Done

Then return to Reinstall Mac OS

Thanks IngoX, I was reading about creating a partition but I didn't do it because I don't know enough about the process, and because I was getting an 'Are you sure?'-type message that suggested doing something similar. But it looks a likely course of action – thanks again.

 

[Fishrrman]

OP:

You need to erase THE ENTIRE DRIVE to go back to High Sierra.

BEFORE GOING FURTHER... you ARE backed up, are you not?
If not, you're going to lose everything, because we are going to WIPE OUT the internal hard drive and "start over".

It looks like IngoX described the procedure, but I'll post mine anyway:

Assuming that you have a good, bootable USB flash drive with the HS installer on it (it appears that you do).... do this:

1. Boot from the USB installer.
2. It should present the OS installer, but DO NOT run that yet.
3. Quit the OS installer and open disk utility.
4. VERY IMPORTANT: go to the view menu and choose "show all devices".
5. Look at the list on the left. The TOPMOST line should be the physical drive inside. This is what we need to erase.
6. Click the erase button. Erase the drive to "Mac OS extended with journaling enabled, GUID partition format".
7. When done, quit disk utility and open the OS installer.
8. Start clicking through -- when it asks WHERE to install, select the internal drive and "click onward".
9. The Mac will restart one or more times, and the screen may go dark for a minute or two with no other indication of activity -- be patient.
10. When the install is done, you should see the initial startup display (choose your language).
11. Start clicking through. At the appropriate moment, setup assistant will ask if you wish to migrate from another drive.
12. YES, you do want to do this. Connect your backup and point the way for setup assistant.
13. Setup assistant will take a little time to digest everything. Be patient.
14. Select what you wish to migrate and turn SA loose.
15. When done, you should see your old login screen, so log in and look around...

Good luck.

 

[Waikiki_61]

OP:

You need to erase THE ENTIRE DRIVE to go back to High Sierra.

BEFORE GOING FURTHER... you ARE backed up, are you not?
If not, you're going to lose everything, because we are going to WIPE OUT the internal hard drive and "start over".

It looks like IngoX described the procedure, but I'll post mine anyway:

Assuming that you have a good, bootable USB flash drive with the HS installer on it (it appears that you do).... do this:

1. Boot from the USB installer.
2. It should present the OS installer, but DO NOT run that yet.
3. Quit the OS installer and open disk utility.
4. VERY IMPORTANT: go to the view menu and choose "show all devices".
5. Look at the list on the left. The TOPMOST line should be the physical drive inside. This is what we need to erase.
6. Click the erase button. Erase the drive to "Mac OS extended with journaling enabled, GUID partition format".
7. When done, quit disk utility and open the OS installer.
8. Start clicking through -- when it asks WHERE to install, select the internal drive and "click onward".
9. The Mac will restart one or more times, and the screen may go dark for a minute or two with no other indication of activity -- be patient.
10. When the install is done, you should see the initial startup display (choose your language).
11. Start clicking through. At the appropriate moment, setup assistant will ask if you wish to migrate from another drive.
12. YES, you do want to do this. Connect your backup and point the way for setup assistant.
13. Setup assistant will take a little time to digest everything. Be patient.
14. Select what you wish to migrate and turn SA loose.
15. When done, you should see your old login screen, so log in and look around...

Good luck.

Thanks Fishrrman for your detailed response! It's much appreciated.
To answer your question, the files on my hard drive is backed up on portable hard drives. I have never used Time Machine, so I have yet to use it to make a backup of the present setup to do a migration from. Is this what you're referring to in step 11?
What will happen if I say No to the setup assistant in step 11? Will the process continue without adding any of my files?

Many thanks again.

 

[Fishrrman]

You don't have to migrate using setup assistant if you don't want to.
Your choice.
But again -- BE SURE that you have stuff you want to keep backed up somewhere before you erase the drive.

The BEST WAY to back up what is on the drive right now would be to download CarbonCopyCloner and create a cloned backup on another external drive.

CCC is FREE to download and use for 30 days, doing this will cost you nothing.

Then, use it to restore (again, using setup assistant).

 

[Waikiki_61]

You don't have to migrate using setup assistant if you don't want to.
Your choice.
But again -- BE SURE that you have stuff you want to keep backed up somewhere before you erase the drive.

The BEST WAY to back up what is on the drive right now would be to download CarbonCopyCloner and create a cloned backup on another external drive.

CCC is FREE to download and use for 30 days, doing this will cost you nothing.

Then, use it to restore (again, using setup assistant).

For sure – everything will definitely be backed up. I will definitely start using Time Machine though, and thanks for the tip about CCC. Appreciate it.