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.