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Fixing an Unfinished Mac OS-X Update

Windows famously had the Blue Screen of Death, when the computer was hopelessly frozen in an error state; Macs have the spinning Rainbow Wheel or Beach Ball that often also spells doom. I thought of those recently when I faced a dead computer interrupted mid-upgrade.

While recently upgrading the operating system on my MacBook Pro, I got this screen:
Nothing but a greyish-white backdrop and a darker grey circle-slash in the center. When I'd power down and back on, same thing. It was well and truly stuck mid-upgrade.

How do you fix a Mac when an OS X upgrade fails in the middle of its upgrade?

The first question to ask is: did the upgrade package successfully download?

Your upgrade could get stuck at the download stage, before ever getting to the installation of the upgrade itself. If you are having trouble with downloading the upgrade, you might try:

  • Plug in the network cable - WiFi is great, but it is slower and prone to its own set of issues with maintaining the connection. And these upgrades are very large files to download, so the connection needs to be maintained for a long time. Eliminate one potential source of trouble and speed things up by plugging your Mac directly into your router or network.
  • Are you downloading through the App Store? Try cancelling and restarting the download. Cancel it by going to the App Store and the software being downloaded. Highlight it and press Option + Alt. This should provide the option to cancel the download. Click OK. Once it is cancelled, you can try to restart the download.
  • Go directly to the source by downloading from the Apple support website instead of the App Store. It is currently support.apple.com Open the website and search for the application upgrade you are looking for. In my experience, the higher results of the search will direct you back to the App Store, but farther down the list will be a link to the download from the support site itself. For example, when I searched for "OS X Upgrade High Sierra 10.13.2" the attached image shows the seventh link on the page, and its download does not come from the App Store.


Now, let's assume that you have successfully downloaded the upgrade package. The next question is whether the upgrade process has truly stopped in a hung state or if it is just taking a very, very long time.

This is important to get right. Interrupting an upgrade that is not truly stalled can cause a loss of data. You did back up the computer first, right?

If the screen shows the upgrade progress bar, possibly with the spinning beach ball cursor, it may not have moved in a while. Even when it does move, it may seem erratic, jumping from one estimate to another. (There is brains behind it, but a lot of factors can make its display progress rather non-linear.

The first thing to do is to give it a while longer. Plug in the power and set it aside to do its thing for a few more hours.

Alternately, press Command-L to access a little more information. It will ideally show what is currently being worked on by the installation.

Once you have confirmed that something has gone wrong and the upgrade installation has indeed frozen, there are several options to try.

  • Do a hard-restart of your Mac. Press and hold the power button until the machine shuts off. Count to ten then turn it back on; Hopefully the intelligence in the installation will either back out and let you restart it, or continue where it left off
  • If you downloaded the upgrade package through the App Store, go back to the App Store and click on Updates. Hopefully the intelligence built into the App Store will resume the upgrade
  • After powering off the computer, hold the Shift key while it powers back on. This launches "Safe Mode" on the Mac. Then go to the App Store and try the installation or upgrade in Safe Mode. Be sure to reboot again once the installation completes
  • An even more drastic measure is to reset the NVRAM. The NV stands for Non-Volatile, meaning that this part of the RAM does not lose its contents when the power is turned off. While restarting the Mac, hold down the Command-Option-P-R keys to reset the NVRAM. This is what finally got my OS X installation moving again. Or in my case, it let me restore to the previous operating system, so that I could then start the download-and-upgrade process over again (successfully the 2nd time!)
  • And more drastic still: use Recovery Mode. As with the previous two options, use a key sequence while restarting the Mac. In this case, Command-R launches in Recovery Mode. From there, you can restore a backup from Time Machine, run utilities for disk analysis and repair, install an operating system, etc.

Stalled upgrades and installations are never pleasant, and the issues are so much more severe when the stall happens with an OS X upgrade. Best wishes in getting unstuck!

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