macOS Mojave Failing to Install on an External USB Drive? Here’s the Fix

MacBook Pro lid with external SSD

If you’re trying to install macOS Mojave on an external drive connected to your USB-C and Thunderbolt 3 equipped Mac and get the dreaded No Entry (circle with a slash) screen, there’s an easy fix.

MacBook Pro lid with external SSD

Here’s the scenario: You connect a USB drive to your Mac with a USB A to USB-C adapter, or with a USB-C to USB-C cable and start the macOS Mojave installation. When your Mac reboots to continue the installation you see a black screen with a white circle and slash. The installation is dead in its tracks.

Here’s the fix: Connect the drive to a Thunderbolt dock instead. In our tests that consistently fixed the problem and let the macOS Mojave installation complete. It even worked when we switched to a Thunderbolt dock after seeing the No Entry screen. We had to reboot after moving the drive to the Thunderbolt dock, and the installation picked up where it left off.

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