Fix for prohibitory symbol (do not enter, stop sign) when booting into or updating macOS Mojave 10.14 beta

Over the last week, I encountered the dreaded Apple “prohibitory symbol” — do not enter sign or stop sign — twice: once when just booting into macOS Mojave 10.14 beta 4 and again when updating to macOS Mojave 10.14 beta 8. Here’s what my MacBook Pro’s screen showed me:

The is one of the symbols that users of Apple products running macOS rightfully fear. Of course, we’re talking about products like the Mac Pro, Mac mini, iMac, MacBook, MacBook Air, and MacBook Pro.

When you see the prohibitory symbol, please don’t panic. Please don’t go through any lengthy reinstalls or plunge down the troubleshooting rabbit hole before you hear me out. Apple says you should “try reinstalling macOS using macOS recovery.” Another Apple support page suggests that you “revert to a previous version of macOS if you experience trouble after installing an update” (using Time Machine). Several Apple forums advise booting from a recovery hard drive, reinstalling macOS, repairing your hard drive with Disk Utility… These are all valid solutions… ones you should only use after trying something simple first.

I was able to solve both my boot problem and update problem with simple solutions. Let’s talk about what I did.

Prohibitory symbol displayed when booting into macOS Mojave 10.14 beta 4

When I saw the prohibitory symbol, I held down the power button until the Mac shut down. I waited at least one minute. I pressed the power button to start my MacBook Pro, used the Startup Manager to select my macOS Mojave 10.14 beta 4 startup disk so an arrow appeared pointing to that bootable Mojave startup drive, clicked on the arrow, and macOS booted up perfectly. You should use the Startup Manager as described here:

  1. Press and hold the Option key immediately after turning on or restarting your Mac.
  2. Release the Option key when you see the Startup Manager window.
    If your Mac is protected by a firmware password, you can release the key when you’re asked to enter the password.
  3. Select your startup disk, then click the arrow under its icon, or press Return.
    If you press and hold the Control key during this step, your selection is saved in Startup Disk preferences, so it persists until you change it.

IMPORTANT: When you first see your bootable devices show up, you may not see all of them immediately. Always be patient so that the Startup Manager has time to scan for all connected drives and display them on screen.

That was easy. Perhaps there was a glitch while my Mac was initially looking for a bootable drive. These things happen. That’s why you should never panic.

Prohibitory symbol displayed when updating from macOS Mojave 10.14 beta 4 to macOS Mojave 10.14 beta 8

I had heard that Apple had released versions of Mojave newer than the one I initially installed. I had been promoted several times by Mojave to update, but ignored those prompts for severals weeks. Earlier today, I decided it was time for me to be running the latest version of Mojave beta. Here’s what happened:

1) I initiated the update process by going to the Apple menu and selecting About This Mac. The About This Mac window opened with the Overview tab highlighted. I then clicked on Software Update… (highlighted in red):

2) The Software Update window opened and informed me that “macOS Mojave Developer Beta 8” was available. I clicked the Update Now button (highlighted in red):

3) I was prompted with an informative confirmation screen. I clicked the Install Now button (highlighted in red):

4) I was prompted with a dialog which informed me that “To update, you must restart your Mac.” I clicked the Restart button (highlighted in red):

5) My MacBook Pro restarted and then showed me the generic Apple progress bar:

6) I patiently waited… UNTIL I GOT THE DREADED … prohibitory symbol:

7) Instead of panicking, restoring from backup, reverting OS version, running diagnostics, etc., I trusted my instincts. I pressed the power button until my MacBook Pro powered down.

8) I waited a bit longer than a minute.

9) I pressed the power button and my MacBook Pro powered on. I used the Startup Manager as described above (and at the link), holding the option key down as soon as I heard the Apple chime.

10) Remember to give the Startup Manager enough time to scan for and show all your connected bootable drives.

11) When it was time for me to pick a boot partition/drive, I did not select the one with macOS Mojave 10.14 beta 4 installed. I selected the one named macOS Installer:

11) Now that the arrow was pointing to macOS Installer, I clicked it to finish the probably failed or interrupted macOS update process.

12) The installer showed me that it was calculating how much time it estimated updating would take. Then it showed me progress as it performed the update:

13) BE PATIENT. The update process may take awhile. When the progress bar reaches the end of the estimated processing time marker, the screen may go black. In fact, the screen may go black at several points during all these steps. BE PATIENT.

14) Look ma! I’m all updated to the currently latest available version of macOS, Mojave 10.14 beta 8!


Hope this helps. With software, being patient and not panicking are virtues. I know it’s a fast-paced world out there, but fretting won’t doing anything for you but waste energy.

Author: Andrew Jaffee

Avid and well-published author, software engineer, designer, and developer, now specializing in iOS mobile app development in Objective-C and Swift, but with a strong background in C#, C++, .NET, JavaScript, HTML, CSS, jQuery, SQL Server, MySQL, Oracle, Agile, Test Driven Development, Git, Continuous Integration, Responsive Web Design, blah, blah, blah ... Did I miss any fad-based catch phrases? My brain avatar was kindly provided by under a Creative Commons Attribution-NoDerivs 3.0 Unported license.

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