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Migration Assistant & User IDs

Alwis

macrumors regular
Original poster
Jan 12, 2017
115
43
Today I picked up my new iMac and now I am unsure how to best use the data from my old 2014 iMac with the Migration Assistant while preserving the numerical user ids.

My 2014 iMac has all Catalina updates installed, including the supplemental update from August. This fixed a memory leak in the kernel. I noticed that problem not only when using VMs but also with high disk io load.

So I guess, that update should be installed before migrating the data but I assume, that the new iMac ships without this update. But when I want to update before migrating the data, I have to create a user first and can not use the Migration Assistant during initial setup. Therefore one of my user ids can not be recreated when migrating my data.

My idea for a workaround would be to create several (e.g. 7) dummy users on the new iMac, than logging in as the last dummy user, which would have uid 507, and delete all users with ids 501 - 506. After migration I would log in with one of my original accounts and delete the user with the id 507.

This would free up these ids, so that the migration assistant could recreate the original user ids. The big question is: Will this work as intended?

I could also try migrating without updating my new iMac before that, but I am nit sure if the assistant will allow migrating from a higher OS version to a lower, even if it is only a supplemental update and there is the risk of a crash during migration.

Thanks for your help!

Alwis
 

Rastafabi

macrumors 6502
Mar 12, 2013
294
137
Europe
You might also try downgrading you current install by rerunning an older installer not including the fix on top of your current install. this way you could just use the migration assistant. To do so just download the desired version using the following terminal command and run the installation.

Code:
softwareupdate --fetch-full-installer --full-installer-version 10.15.5
 
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Taz Mangus

macrumors 603
Mar 10, 2011
5,073
1,229
So I guess, that update should be installed before migrating the data but I assume, that the new iMac ships without this update. But when I want to update before migrating the data, I have to create a user first and can not use the Migration Assistant during initial setup. Therefore one of my user ids can not be recreated when migrating my data.

My suggestion is turn on the computer, connect your backup drive to your computer and select to use Migration Assistant to create the user accounts. Then apply the Catalina OS update if there is one. The iMac might already have the 10.15.6 Supplemental update already applied before it shipped to you.

Doing Migration Assistant first and then the system update won't affect the migration of user data.
 
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Alwis

macrumors regular
Original poster
Jan 12, 2017
115
43
Thanks for your suggestions!

You might also try downgrading you current install by rerunning an older installer not including the fix on top of your current install.

Whow, I did not know that downgrading is possible...

Doing Migration Assistant first and then the system update won't affect the migration of user data.

Without the supplemental update I had several crashes when using an external hard drive and writing a lot of data to it (using rsync). I fesr, that this could also happen during the migration.
 
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Taz Mangus

macrumors 603
Mar 10, 2011
5,073
1,229
Without the supplemental update I had several crashes when using an external hard drive and writing a lot of data to it (using rsync). I fesr, that this could also happen during the migration.

With Migration Assistant you will be reading from the external drive, not writing to the external drive unless you plan on moving the user accounts to an external drive.

The other option would be to not use Migration Assistant, create the user accounts, apply the Catalina update (if that is even needed) and then do a manual migration of user data from the backup drive.
 
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Alwis

macrumors regular
Original poster
Jan 12, 2017
115
43
With Migration Assistant you will be reading from the external drive, not writing to the external drive unless you plan on moving the user accounts to an external drive.

I am not sure if the crashes where triggered by writing or just by transfering a lot of data via USB, that I was writing to the drive might have been a coincidenc.

The other option would be to not use Migration Assistant, create the user accounts, apply the Catalina update (if that is even needed) and then do a manual migration of user data from the backup drive.

I considered doing this, as my current Mac installation originates from 2010, but that would take some time.
 
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Taz Mangus

macrumors 603
Mar 10, 2011
5,073
1,229
There is another way that might work for you. When you receive the computer, turn it on and setup it as a new computer by creating a new admin that does not exist on your backup. Apply the Catalina update and then follow the steps in the link below, this will force Migration Assistant to be rerun. When Migration Assistant completes remove the new admin account.

 
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Alwis

macrumors regular
Original poster
Jan 12, 2017
115
43
Thanks, that seems exactly the solution i was looking for!

In the meantime I had an other idea to: Create a new admin during setup (which will geht the user id 501) and than use the migration assistant to migrate the data of all accounts except the admin account.

Then I would migrate the files from the admin account manually to the new admin account. This would be feasible, as I do not use the admin account for my daily work, so there would not be mich to migrate.
 
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Alwis

macrumors regular
Original poster
Jan 12, 2017
115
43
Once again thanks a lot for all the input!

At the end I went with my last idea: Created the first two accounts and copied the data manually. Than I used the migration assistent in two passes for the rest. Now all my accounts have the same user id on booth Macs, as intended!
 
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