Failed restore from time machine and iMac doesn't boot any more

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Failed restore from time machine and iMac doesn't boot any more

Hi,

I have a iMac (Retina 5K, 27-inch, late 2015) bought new in 2017. It had a fusion drive: a 2 TB HHD plus a 128GB SSD. It had Catalina installed.

I had a Time Machine automated backup in a USB drive.

On Nov 10 it stopped booting: the boot process kept being stuck on the Apple logo and the progress bar.

It had a call with Apple support (very reactive - thanks), and did a few tests with them. Turns out that it needed repair. I brought my iMac to an Apple authorized repair shop, which diagnosed that my HDD was faulty and changed it with a 2TB SSD, with a fresh Catalina install.

I brought the iMac back home, plug my USB Time Machine on it, and at startup asked to restore from my latest Time Machine backup.

The restore process progressed with hundred of thousand of items processed, and it left it like that during the night.

Unexpectedly, on morning the iMac screen was on Recovery mode (https://support.apple.com/en-us/HT201314). I restarted the iMac, but it failed to boot, a prohibitory symbol being displayed right at the start.

I restarted through an Internet Recovery, and using the disk util, I get this (in French, sorry):

At that point restoring from Time Machine doesn't work (no target disk available). Re-installing Mac OS from Recovery mode doesn't work (get stuck right at the beginning of the process).

There seems to be something wrong with the new disk. A hardware failure at this point seems highly unlikely. What should I do?

Thanks

iMac 27″, macOS 10.13

Posted on Nov 25, 2020 1:06 AM

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GoodYoyo Author

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Nov 30, 2020 12:31 AM in response to GoodYoyo

If it can help someone, here is how it got solved.

The hard drive seemed to be in an inconsistent state. 'diskutil resetFusion' was performed after having booted through internet recovery. But at that point neither MacOS install nor Time Machine restore from the Recovery screen worked.

The trick was actually to remove the Fusion drive, which doesn't bring any value with two SSD, which I did thanks to: https://medium.com/@ObjSal/split-fusion-drives-in-macos-mojave-a10523f1819f .

After that, Big Sur install from Internet Recovery was performed successfully.

An admin account was created to access Big Sur, and from this account a Time Machine restore was launched using Migration Assistant.

The Time Machine restore finished without error (more than 3 hours for the preparation phase without any visible progress, more than 12 hours for the full restore, around 3M files restored).

But out of the 3 accounts restored, log-in with the main one didn't work (spinning wheel forever after the password screen).

To overcome this last difficulty, I had to log with the newly created admin account, delete the blocked user, while keeping the files, rename the home directory of the home user (to which "deleted" had been added), and re-create a new user with the same name.

And in the end, it worked! Seems like all apps, documents and settings have been successfully restored!

Special thanks to Apple support which was there to help all along the way.

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Failed restore from time machine and iMac doesn't boot any more

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