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OT: be cautious when upgrading your MacOS to High Sierra


We have a Mac Mini that was running Sierra.

  • Two days ago… an employee attempted to upgrade to High Sierra.

The upgrade failed miserably.

I spent hours on the phone with Apple Enterprise Support… and they couldn’t fix it.

Apple has “Consumer Support”…

  • and then they have “Enterprise Support” (which is suppose to be better).

Enterprise Support is specifically tailored for businesses… as opposed to “consumers”.

Even though my computer was out of warranty… and I spent 4 hours on the phone with them

  • it didn’t cost me one penny.

Anyways - to continue… at the end of the upgrade process

  • I would get an error message saying
  • “MacOS High Sierra could not be installed on your computer. Restart to try again.”

“Trying again” was the only option.

No matter what I did… including powering off the computer and doing a cold start…

  • resulted in the Mac “trying to install” High Sierra.

There was no option to to cancel the upgrade… and just use Sierra.

I spent almost 18 hours trying to get our of “hell-of-a-loop”.

I also tried reinstalling the OS via the Recovery Drive…

  • but then I realized… the recovery drive had already been over-written with High Sierra.
  • and that’s why the computer kept trying to install High Sierra.

High Sierra was already installed… but the Mac didn’t know that.

  • apparently the Mac thought it was running a previous version (Sierra).

So basically every time I tried to recover the OS…

  • the system would try to install High Sierra (again)…
  • which would put me right back in the endless loop.

Luckily… I remembered (after 14 or so)

  • that I previously disconnected an external drive from the computer a few days earlier.

That external hard drive
contained a full backup of the Mac… including the Data / the OS / and the Recovery Drive.

The software is called “Carbon Copy Cleaner” from a company named Bombich.

Here’s their URL:

I attached the external hard drive… and it took forever

  • but the system booted to a Sierra Recovery drive…

and with that

  • I was able to reinstall Sierra onto the Mac…
  • thus fixing the issue and ending a nightmare.

I say “ending a nightmare”

  • because, as a business… we file taxes quarterly…
  • and this was our accounting computer
  • and our quarterly taxes are due in 7 days.

If it wasn’t for the Carbon Carbon software…

  • we would be manually entering in financial data.

The first question you should ask is…

  • didn’t you have a backup ?

The answer… Yes. Time Machine. And it seems Time Machine failed to backup the financial data.

I’ve checked… the entire drive was supposed to be backup… (after seeing the log file)

  • it appears Time Machine had a read / write error with the data.

So if you want to upgrade to High Sierra… I’d delay it for a while… until Apple can figure out what the problem is
If you are using Time Machine… verify that backup information is actually being backed up
take a look at Carbon Copy. It literally saved our a$$.

Carbon Copy Cloner. Highly Recommended.

Thanks for the heads up! Nearly upgraded just now, glad I stumbled upon your post. :raised_hands:

I ran into the same problem with a iMac late 2012. A newer MBP upgraded without any problems. With the iMac I tried several times with different techniques but ended up with erasing the disk and start over. Luckily my files live in iCloud so I all I had to do was reinstall som software. Most of them are Mac Appstore apps.

Hope it can be solved for you soon.

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