Safe mode (sometimes called safe boot) is a way to start up your Mac so that it performs certain checks and prevents some software from automatically loading or opening. Starting your Mac in safe mode does the following: Verifies your startup disk and attempts to repair directory issues, if necessary.
Apple recently released a very useful support page to assist Mac users in basic troubleshooting by utilising this special start up mode. If your Mac doesn’t have a keyboard available to start in safe mode, but you have remote access to your Mac, you can configure the Mac to startup in safe mode using the command line.
If you run into macOS Sierra installation problems you may need to try installing in Safe Mode. Some users report that their macOS Sierra installation freezes and requires them to restart the Mac and start over. When this happens you should try uninstalling any antivirus software that you are running. If macOS Sierra installation problems persist, try booting in safe mode. Hold the Shift key while you press the power button and keep holding the shift key. This will start your Mac in Safe Mode. Once in this special mode, try installing macOS Sierra again.
To exit Safe Mode, restart your Mac like you normally would (choose Apple menu > Shut Down) but don’t hold down any keys during startup. You should be back to your desktop in normal mode. Keep in mind that leaving Safe Mode might take longer than it does to boot in normal mode.
If you have macOS Sierra, you must boot to macOS Recovery before you can run this command.
- Access the command line by opening Terminal remotely, or logging into the computer using SSH.
- Use the following Terminal command:
sudo nvram boot-args="-x"If you want to start in verbose mode as well, use this instead:
sudo nvram boot-args="-x -v"
- After using safe mode, use this Terminal command to return to a normal startup:
sudo nvram boot-args=""
See also our useful post on “Startup Problems“