Downgrading from Catalina to Sierra on a 2012 MBP

[Scoot65]

I've just bought a 2012 13" MBP. The seller had replaced the original HD with a larger one and has installed Catalina on it. I wish to downgrade back to Sierra.

My wife has a the same model MBP and I have a backup bootable clone of her MBP (done via Carbon Copy Cloner).
Can I simply connect the bootable clone external HD to the 'new' MBP, select the clone HD as the start up HD, reboot from that and then erase the internal HD (changing the format from APFS to Mac OS Extended Journaled). Once it's erased, install from the cloned external HD and that's that?

 

[Audit13]

Yes, that would work.

 

[Scoot65]

Thanks for the reply. I've just finished..... and now I have problem!

I booted from the external clone HD, erased the internal HD which was APFS and had Catalina on it. I erased it and set it to Mac OS Extended Journaled.

I then cloned the internal HD using the backup external HD. All went well and 95GB was copied in approx 35 minutes.

When the process was complete, closed Carbon Copy Cloner, selected the internal HD start up disk and restarted.

Upon restart, I noticed that only "CCC Backup" was showing on the desktop tp right hand corner rather than "Macintosh HD" which I had named as the destination.

Now, only the external HD is shown in System Preferences > Start updisk no other HD is shown.

In 'about this Mac' only "CCC Backup and optical drive is shown under storage, no Macintosh HD.

I relaunched Carbon Copy Cloner and it's showing 'CCC Backup" as source and the destination says "Macintosh HD - this volume is missing"

I've done a restart in case that sorted things, but still have the same problem....

So it looks like I've managed to lose the internal HD ....... HELP PLEASE !!!

 

[Audit13]

This is weird.

I've used CCC a few times and it's always worked for me.

I buy Airs that are defective in some way so I can mix and match parts to create a single, working unit.

I have a CCC Backup of High Sierra and use it to restore the OS to different MacBooks. It's worked for me. I have since switched to Time Machine because that's what people in my family use.

I recommend booting into disk utility, wiping the internal drive again to see if it is visible by CCC. If not, another solution would be to make a Time Machine backup of your wife's machine and TM to restore to the new Mac.

 

[pshufd]

How about disconnecting the external drive? Are the volume names the same? It might not be able to open both drives at the same time.

 

[Scoot65]

Thanks for all the replies. Very much appreciated.
I've done as Audit13 suggested, rebooting into Disk Utility and re-did the whole cloning process again.

I'm very pleased to say that this time, everything worked as expected and I've got my internal HD back!!

I ejected the external cloned backup HD and I'm running on the internal HD as normal. Everything appears to be OK again.

Thanks again for the replies

 

[subaiku]

Was searching for an answer to a similar problem and thought of posting here instead of opening a new thread. I just got myself a 2012 15" as well that also came with Catalina. I wanted to reinstall High Sierra and made a bootable USB for that purpose. Problem is after I had erase the Macintosh HD drive (APFS format because the drive is SSD) and tried to install High Sierra, I always get this error 'Unable to unmount volume for repair. Quit the installer to restart your computer and try again'

Which I do, booting up from the USB but I keep getting the same error/loop.

Have tried this, but doesn't work for me:

High Sierra install fails - "unable to un… - Apple Community

discussions.apple.com

 

[Audit13]

Was searching for an answer to a similar problem and thought of posting here instead of opening a new thread. I just got myself a 2012 15" as well that also came with Catalina. I wanted to reinstall High Sierra and made a bootable USB for that purpose. Problem is after I had erase the Macintosh HD drive (APFS format because the drive is SSD) and tried to install High Sierra, I always get this error 'Unable to unmount volume for repair. Quit the installer to restart your computer and try again'

Which I do, booting up from the USB but I keep getting the same error/loop.

Have tried this, but doesn't work for me:

High Sierra install fails - "unable to un… - Apple Community

discussions.apple.com

Are you able to install a and boot High Sierra from an external drive?

Is it possible the SATA drive cable is defective? Are you using an internal SSD or mechanical drive?

 

[4sallypat]

Change the date/time using Terminal.
Date anytime for 2017 would work.

Common issue with High Sierra - I have to manually change the time/day/year using Terminal to a day in 2018.

 

[subaiku]

Change the date/time using Terminal.
Date anytime for 2017 would work.

Common issue with High Sierra - I have to manually change the time/day/year using Terminal to a day in 2018.

YES! I did that but before that I found out I also had to delete an extra 'Macintosh HD-Data' volume. Able to install after doing both those steps. Thanks!

But err... I now have a new problem. After installing, I can't reboot from the drive. It keeps rebooting from the USB. I was using the macOS High Sierra Patcher to install so I tried 'macOs Post Install' which installed an APFS patch. And now it keeps rebooting into the Apple logo loading screen but it freezes with no progress at the loading bar.

Any ideas guys?

 

[4sallypat]

At startup chime, hold down the ALT/option key and when it shows the types of startup drives, what do you see ?

 

[subaiku]

At startup chime, hold down the ALT/option key and when it shows the types of startup drives, what do you see ?

I see a drive called EFI Boot. Clicking on it gets me the same freezed Apple loading page.

I am however able to reboot in safe mode though.