Solving Mac OS upgrade failure with blank screen


October 2, 2017 by

If your Mac fails to complete an OS upgrade, locking up at a blank screen with an arrow cursor in the upper left corner, solving the problem might be easier than you think.

There is a known issue when upgrading the Mac OS, where the computer locks during the final stages of the process. I ran into this problem when upgrading my Mac to the High Sierra OS.

If you search for solutions online, you will find a number of articles explaining how to restart your Mac in a special way and then enter a series of commands to correct the problem.

While I am sure that these methods would be successful, in my case I discovered an easier way.

The easy way

Unplug any USB drives connected to the Mac.

When I disconnected my USB drive, the OS upgrade completed successfully after restarting the Mac. Once the upgrade was complete, I plugged the USB drive back in and was back in business.

The hard way

Hopefully unplugging the USB drives will work for you, too. If not, here is the process you need to follow:

  1. If the Mac is still on, press and hold the power switch for several seconds to force the Mac to power off.
  2. Press and hold the command and s keys; then, press the power switch to turn on the Mac.

    Lines of text should display on the screen, indicating that you are in a mode where you can enter commands.

    Note: Make sure that the system has completely stopped displaying text before entering any command.

  3. Type each of the following commands, pressing the return key after each command. Commands are case-sensitive. Make sure that you enter spaces as shown.
    1. /sbin/fsck -fy
    2. /sbin/mount -uw /
    3. rm -f /Library/Preferences/
    4. rm -f /var/db/.AppleUpgrade
  4. When the system stops displaying text, press and hold the power switch for several seconds to force the Mac to power off.
  5. Press the power switch to turn the Mack back on.

The system should continue the installing the OS and restart normally. After you log in, you can reconnect your USB drive.

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