MacOS – Downgrade macOS 10.14 to 10.13 using Migration Assistant

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I am currently running the macOS 10.14 beta on my Macbook and I wish to downgrade to High Sierra (10.13). I do have time machine backups from when I was still on 10.13, but I want to keep all my current files.

Is it a valid idea to instead just do a clean install of 10.13, then use migration assistant to transfer my files from backups when my computer was running 10.14? Can migration assistant even move files from a time machine backup running a later OS to a computer running an older OS?

I am only looking to migrate files and applications. I've done all the development work I needed in 10.14 and no longer need it. I have not added any server configurations or anything like that.

Best Answer

Theoretical answer

This operation will fail.

Migration assistant is a huge procedure made to make all the conversions necessary to go from an older version of MacOS X to the running one.

For example, the Mojave (10.14) version of Migration Assistant is configured to correctly convert the Users and System files from a High Sierra (10.13) set to a Mojave running environment.

The High Sierra (10.13) version of Migration assistant doesn't know the specific changes of Mojave (10.14) because they weren't known at its date of conception. Then this version cannot do a migration from Mojave to High Sierra.

On the other hand, the Mojave version of Migration Assistant does know the specific changes from High Sierra to Mojave but some of them might be not reversible, and this is usually not documented by Apple (this is bad: Apple is convinced none of its users is interested in this information).

Practical answer

Your proposed migrition might succeed (my raw estimate: 25%).

If you didn't made system modification or specific development on Mojave,

and if Apple didn't put in place a basic verification of the origin version of MacOS X, (is the origin version older than the target one?),

then you could try to run Migration Assistant from High Sierra to migrate only Users files from your Mojave backup to your running High Sierra environment.

Experience return

Please add your personnal success or failure as an answer, since this might help many other Mac users.

Related Solutions

How to migrate data when Migration Assistant doesn’t recognize Time Machine external drive

Have you tried right clicking on the time machine icon on your dock, and telling it to browse other time machine disks? See if Time Machine will recognize it as a backup, and see if it will restore any files that way.

When you select Restore From Time Machine backup it doesn't even see the external drive or list it/any backups?

Mac – Files on new computer are locked after using Migration Assistant and Time Machine

Sounds like the permissions are "wrong" or rather the owner is. Click on the folder, press Command+i, in the "Sharing & Permissions:" section (on the bottom) and check if it shows your new user-account on the MBP as owner (first icon) and if the privileges are "Read & Write".
Probably it will show a different user as owner. You could then try to fix the permissions by running Disk Utility, selecting you OS X partition on the left and click "Repair Disk Permissions" - but maybe this won't fix it, then you have to do it using the Terminal.
Maybe someone else can elaborate on that.

Edit 2011-12-18: Ok, I'll try myself:

Something I didn't know yet but found now looking for an easy fix:

From Troubleshooting permissions issues in Mac OS X

Note: In Mac OS X 10.5 and later, while started up ("booted") from the Mac OS X 10.5 installation disc, a user's home directory permissions can be reset using the Reset Password utility.

But in Lion they removed the option form the menu, so if you boot (holding "alt ⌥") into Recovery HD
- Wait for “Mac OS X Utilities” menu to appear, indicating that you are booted into recovery mode
- Click on the “Utilities” menu and select "Terminal"
- Type the following: resetpassword
- Confirm the user account and then the password change and reboot Mac OS X 10.7 as usual with your new password

Copied from Reset a Mac OS X 10.7 Lion Password

I didn't try it myself, but hopefully this should reset/repair your home directory permissions.

Maybe even better solution using Finder in normal OS X:

In Finder select the folder
Press Command+i
Expand "Sharing & Permissions" section (Unlock if necessary 1)
If you're not in the list of owners, press [+] 2
In the upcoming list, select your new user
Finally click the gear 3, make your new user the owner, apply to enclosed items
- and delete the old user by selecting his name from the list and clicking [-]

test_not_owner_arrows

Easiest way, if you're not afraid of the terminal:
Assuming your new user is named harmen

sudo chown -R harmen /Users/harmen

This will make you the owner of everything inside /Users/harmen
Read more here

Good luck.