Upgrade/Downgrade between Mojave and Catalina (incl Bootcamp); user folder on external SSD

[Beliblis]

Hi,

I would like to upgrade from Mojave to Catalina (or Big Sur), but am a bit reluctant to do so because of Catalina's weird new dual-volume HD-Setup. (Guess Big Sur needs the same HD structure, right?)
Main reason to upgrade is because of the sidecar feature (don't want to get an Astropad subscription). And if I find software compatibility issues, I may have to downgrade to Mojave again.

My 2018 MacMini's setup is a little 'different' I believe:

• my user folder is on an external 1TB SSD (don't like the soldered-on internal hard-drive; in case of hardware problems it's easier to retrieve user folder from the external SSD)
• the internal 512gb drive only holds MacOS and Bootcamp

If I understand things correctly, upgrading to Catalina will automatically change the internal HD-structure to 3 partitions: 2 for Catalina, 1 for Bootcamp. So the upgrade to Catalina should be straight-forward. Is that correct?

But how about if I want to downgrade to Mojave again? Would I have to completely reformat the internal drive, then install Mojave and Bootcamp again from scratch? (Which would be a nightmare... I'm running an eGPU and it took a while to set up Bootcamp/drivers correctly for that eGPU to work reliably under Windows).

In case this makes downgrade easier: I've got several large external hard-drives with backups, and Carbon Copy Cloner.
Is it possible to do an exact 1:1 clone of my current internal HD (Mojave AND Bootcamp) which I could then clone back if I'm not happy with Catalina?

Many thanks for your help!

 

[Fishrrman]

Your solution:

BEFORE you attempt the upgrade, use CarbonCopyCloner to create a bootable cloned backup of your current Mojave install on an external drive (SSD or platter-based hard drive).

TEST the cloned backup, to make sure you can boot from it.

Once that's done, disconnect the cloned backup and set it to a safe place.

NOW you're adequately prepared to attempt the upgrade.
If things don't go as planned, or if you don't like it, you can do this:
a. connect the backup
b. BOOT FROM the backup
c. use disk utility to ERASE the internal drive COMPLETELY**
d. use CCC to "re-clone" the backup BACK TO the internal drive.

... and, having done this, you'll be "right back where you started from".

If you DON'T take these precautionary steps before upgrading, you might still "get back", but it's gonna be a long, hard road.

** To completely erase the ENTIRE drive, you must open disk utility and then go to the "view" menu and choose "show all devices".

 

[Beliblis]

Thank you @Fishrrman.
What about Bootcamp and the user-folder on my external hd?
I've attached a screenshot from disk utility

1. I'm guessing that updating to Catalina will keep the /userfolder path the way it is, right? (in my case /Volumes/BDRIVE/username)
   That external drive contains mostly user folder data of course – but also the library folder with application settings, Apple Mail data, etc.
   Would you anticipate the drive to be backwards compatible if I downgrade to Majoave again?
2. Or can the 100gb Bootcamp partition cause problems during the upgrade to Catalina? Or will the upgrade automatically split the 400gb MacOS partition into 2 parts, and treat the Bootcamp partition as if it were a separate physical hard drive
3. If I want to go back to Mojave and follow your step c) to ERASE the internal drive completely: What would that do to my Bootcamp partition? (When I backup my Bootcamp partition, CarbonCopyCloner tells me "The destination volume will not be a bootable backup of your Windows installation" (CCC's website doesn't offer that functionality and refers to Winclone instead)

Sorry to ask so many questions and in such detail. I consider myself fairly experienced after nearly 2 decades of MacOS. And I've done plenty of backups, bootable partitions, etc.... but never really got my head around Catalina's new dual-volume approach. (First thing I did when I got my MacMini with Catalina preinstalled was to downgrade to Mojave).

It'd be great if there was some kind of "sector-by-sector hard drive cloning software" which clones the entire physical hd (all partitions in one go). CCC only gives the option with Winclone (step 5 and 6 here: https://www.startupcto.com/server-tech/macosx/mac-internal-drive-upgrade

Sector-copying incl all partitions exists for Windows as far as I know. Do you know if there is something for Mac?

 

[Fishrrman]

"Would you anticipate the drive to be backwards compatible if I downgrade to Majoave again?"

No. You'll have to COMPLETELY ERASE the drive and start over to get back to Mojave. Catalina completely changes how the OS exists on the drive. Big Sur is even "more changed".

"If I want to go back to Mojave and follow your step c) to ERASE the internal drive completely: What would that do to my Bootcamp partition?"

I don't use bootcamp, can't help you there. I've heard others say the windows partition can be cloned with winclone. I have nothing more to offer except to say that "going back" (erasing the drive) WILL wipe out bootcamp. You'll have to start over with that too.

Let me offer an alternative:
Get an external SSD. Doesn't need to be big -- 256gb will do. They're cheap.
Get an external USB3 enclosure for it (if it doesn't have one).
Install Catalina (or Big Sur) onto the EXTERNAL DRIVE and play around with it that way.
If you do this, you can "test out" a new OS, without really disturbing your internal drive.

I've been doing this for many, many years to check out new versions of the Mac OS before I "commit myself" to them.
Works for me.

 

[Beliblis]

Thank you again – very helpful.
Your alternative solution with Catalina on external HD sounds perfect. Should have thought of it myself – with my old 2012 MacMini I had an external system HD for some time.

Only problem I can see is Mail Library, but that would be the case with downgrading any OS. I prefer POP to IMAP, and apparently once updated, the Mail Library isn't backwards compatible.
Solution would be manual export/import of elmx files. Or work with another mail client temporarily (using IMAP), until I commit myself to the new system.

 

[JKary]

Hi
On my Mac Pro mid 2010 with Mojave 10.14.6, I did clean install, but when I tried to download my apps from AppleStore ,(Logic 10.5.1,Motion ,iMovie etc ) it Was inpossible.The apps was for Mac OS 10.6.1. Maybe because a few days ago , I had installed in my Mac book pro Catalina os, with the same Apple ID as in Mojave that I have in my Mac Pro 5.1.
Can someone help me ,how can I recover the apps I purchased for Mojave ?
Thanks a lot

 

[saudor]

You will lose your bootcamp partition even with carbon copy cloner. In my case i use acronis true image (perpetual license) to clone both mac and bootcamp partition but again you're relying on 3rd party software which means the restore process may not go so well

Acronis likes to glitch up especially when dealing with these multi volume installs. Plus it has too many junk running in the background (i had to chmod -x a lot of these so they wont run)

As someone said, winclone can also clone the bootcamp partition separately

 

[JKary]

Thanks Saudor ,I will try ..