Downgrading from Catalina to Sierra on a late 2014 iMac

[moosed]

Long story short... I need to downgrade to a pre 'High Sierra' operating system to see if it solves image retention issues on my 5k iMac which originally started with the installation of High Sierra. I originally thought it was a hardware issue but after lots of research it seems it's something which started with High Sierra and is software based (same issue does not exist for people when downgrading from high Sierra to Sierra or when running windows via bootcamp etc).

How does one go about downgrading to Sierra ? Where I can find the Sierra installer ? It's no longer available on the apple store.

Also if I do a completely fresh install am I going to encounter issues where it tries to tell me I cant install Sierra on my Mac as it's too old ? Even though I got the Mac in 2014... I seem to remember reading something about Apple making it a massive ball ache for anyone to downgrade even after reformatting the system drive. Perhaps something do with with APFS to HFS+ ?

 

[glenthompson]

It can be done since your iMac predates Sierra. Problem is getting a copy of the installer. Here is an article that talks about how:

Sierra download

You will have to revert to a HFS+ fie system. If I was doing this I would get an external SSD and install Sierra on it and then boot from the external.

 

[moosed]

It can be done since your iMac predates Sierra. Problem is getting a copy of the installer. Here is an article that talks about how:

Sierra download

You will have to revert to a HFS+ fie system. If I was doing this I would get an external SSD and install Sierra on it and then boot from the external.

Thanks for the link. At what point do i revert to an HFS+ file system ? When im reformatting via disk utility in recovery mode ?

 

[DeltaMac]

Best choice is to boot to an external bootable installer, so you can format the device, not just the macOS volume.

 

[moosed]

Best choice is to boot to an external bootable installer, so you can format the device, not just the macOS volume.

Yeh that's my plan. I've managed to find the Sierra installer (InstallOS.dmg) My problem now is that when i try and create a bootable sierra USB installer using either 'Diskmaker X' or 'Install Disk Creator' it tells me

"The selected item does not appear to be a valid macOS installer.

It is lacking the file 'Contents/SharedSupport/InstallESD.dmg'

Which suggest the .dmg i downloaded isn't legit but im pretty sure its completely legit

Im downloading Sierra from the link here btw

How to get an old macOS installer from Apple | AppleInsider

Your collection of old macOS installer disk images is now worthless, and Apple has changed where it hides downloadable copies. Yet there are still good reasons to get old OSes, and here's how to do it.

appleinsider.com

 

[moosed]

Well i found an installer, created a booteable drive using install disk creator but i can't select it as the startup drive either from preferences startup disk or when booting the mac via the option key.

Not sure where to go from here

 

[DeltaMac]

You are part of the way there!
Double-click that InstallOS.dmg file.
You will get the file InstallOS.pkg. Double click THAT, which will launch the installer.
Run the install, which does NOT install the system, but simply copies the installer app to your Applications folder, and makes it complete to do the install.
Don't run that installer app. Use that app as the source for your DiskMakerX or Install Disk Creator. Should work this time.
You can also use the terminal, and create a bootable installer using the createinstallmedia command that resides inside the installer app.

sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app

of course, change the parts of the command line to make it conform to your own system directory.
If you are not comfortable with using the terminal, there's an easy way to set up that line of commands.

 

[moosed]

You are part of the way there!
Double-click that InstallOS.dmg file.
You will get the file InstallOS.pkg. Double click THAT, which will launch the installer.
Run the install, which does NOT install the system, but simply copies the installer app to your Applications folder, and makes it complete to do the install.
Don't run that installer app. Use that app as the source for your DiskMakerX or Install Disk Creator. Should work this time.
You can also use the terminal, and create a bootable installer using the createinstallmedia command that resides inside the installer app.

sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app

of course, change the parts of the command line to make it conform to your own system directory.
If you are not comfortable with using the terminal, there's an easy way to set up that line of commands.

edit: I tried both methods (including terminal) and it seems to create the installers ok but the drive never appears as bootable despite appearing on my desktop

 

[moosed]

One other thing, if I get this usb installer working at what point do I have to make sure the drive im installing it to is in HFS+ rather than APFS ? and how do I make it HFS+ ?

 

[moosed]

Ok so after pulling my hair out for the past few hours i have finally managed to create a bootable disk of El Capitan.

It seems creating a Sierra one is impossible. I tried creating one using numerous disk images i found of varying versions, i've tried multiple techniques from Install Disk Creator to Terminal commands and even TransMac on the PC... all installed on the USB ok and appeared mounted on desktop but none were bootable despite me setting them to have a GUID partition as guides suggest.

I noticed that on eBay everyone sells bootable drives for all versions of OSX apart from Sierra... which to me suggests that there is some kind of serious problem with creating bootable versions of Sierra, presumably from macs running Catalina or some other newer version of OSX.

Anyway.

I'm now at the stage where i have to install the operating system but someone in this thread mentioned i needed to change the disk im installing it on from APFS to HFS+.

How, where and when do I do this ?

 

[Fishrrman]

First off -- the only way to get rid of Catalina is to completely ERASE the internal drive and start over. "Nuke it from orbit" as the saying goes.

If you have a USB flashdrive that will boot to El Cap, I suggest you use it.

First -- BACK UP anything you wish to save.
I WOULD NOT USE time machine for this.
I'd use either CarbonCopyCloner or SuperDuper (both are FREE to download and use for 30 days).

Next -- boot from the El Cap drive. Open disk utility. ERASE the internal drive to Mac OS extended with journaling enabled, GUID partition format.

Then -- install El Cap. Get it up and running with a basic account.

At this point, you can investigate trying to upgrade to Low Sierra (10.12).
If you can't get a usable copy of the installer from Apple (I don't know why they make it so hard), then my advice to you is to find it and get it ELSEWHERE, regardless of source.

You might consider paying for a USB flashdrive with a copy of the installer ready-to-go. Folks sell these on ebay.

Try upgrading from El Cap to Low Sierra and see how it goes.
If it goes ok, then restore your data from the cloned backup.