Macintosh OSX Troubleshooting

White screen with Apple Logo and then Prohibitory Symbol

When I power on the Mac I see a white screen with an apple logo in the middle. The apple logo then changes to a circle with a diagonal line though it for a few moments, then back to the apple logo. Nothing else happens. Some people call this "The White Screen of Death" or WSOD, but everything is referred to as some sort of screen of death anymore and the catch phrase is nonspecific.

This issue is caused by, typically, that the Mac is unable to find a valid operating system to boot from. Maybe the startup disk has a corrupted macOS installation. There could be some operating system files missing or damaged. Worse is the possibility of a physical problem with the drive, probably a harddrive.

According to Apple: "A circle with a line through it means that your startup disk contains a Mac operating system, but it's not a macOS that your Mac can use." Apple suggests that you will have to use the Disk Utility (Command + R at boot) and reinstall macOS.

People have experienced this problem after an update, and reboot.

Others have suggested this is caused by unsigned kernel extension (KEXT) files on the hard drive.

The presence of more than one bootable partition seems to sometimes cause this issue.

Selecting the Startup Disk at Boot

Under System Preferences > Startup Disk, ensure it is pointing to your new drive.

Sometimes if it is not, it may eventually find it, but it may take a while.

1. Set the default startup disk.

2. Reset the System Management Controller (SMC) on your Mac - Apple Support