Time Machine restore on a new Mac fails without explanation if target OS is older than back-up's

Number:rdar://45153677 Date Originated:10/10/2018
Status:Open Resolved:
Product:Mac OS Product Version:High Sierra / Mojave
Classification:Data Loss Reproducible:Didn't try
Something not on this list

I recently purchased a new computer and tried to set it up using Migration Assistant. I tried both using a very recent Time Machine back up. The migration summary screen on the target machine showed that around 5Mb of configuration and contact files would be restored; nothing was shown for all my Applications, documents, etc; it appeared as if the back-up had failed or my files were gone forever. I knew my back-up was around 300Gb despite what the assistant was reporting but anyone less technically savvy could have a meltdown from thinking decades worth of photos were gone or that –taking fault themself– they had messed something up. In either case they'd likely call Apple Care (using  resources and time), visit an Apple Store (also using many peoples resources and time) or hit continue and accept that they lost the entirety of their data.

When I then tried to run migration assistant via a direct connection with the old machine via USB 3. It was ONLY THEN that the old computer's migration assistant (on Mojave) altered me that the target/new computer was running an older version of Mac OS. It did not suggest any course of action. Luckily I knew to setup the new machine as a blank machine and then open migration assistant after updating to Mojave. I had planned on dropping this old machine off at the Apple Store when I got my new computer but decided to hold onto it until the transfer was successful (I guess I've learned to mistrust these things). If I had done so I might not have tried the direct connection and ever seen this warning.

This is a really really bad first time experience to say the least and a bug that probably results in a ludicrously unnecessary amount of data loss per day.

* Migration assistant should recognize if a Time Machine back-up is from a newer OS and display a clear warning and offer to upgrade the target machine before migrating or *at the very least* prescribe explicit and clear instructions.


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