MacBook unable to start after update

To resolve a MacBook that fails to start after an update, follow these troubleshooting steps. First, try booting into Safe Mode by holding the Shift key immediately after pressing the power button. This runs a directory check and may allow the update to finish. If Safe Mode does not work, reset the NVRAM or PRAM. Shut down your Mac, then turn it on and immediately press and hold Command, Option, P, and R for about 20 seconds. This can clear corrupted startup settings. You should also try resetting the System Management Controller (SMC) by holding Shift, Control, and Option on the left side of the keyboard while pressing the power button for 10 seconds. If the issue persists, boot into macOS Recovery by holding Command and R during startup. Once the utilities window appears, select Disk Utility and run First Aid on your startup disk to repair potential file system errors. If Disk Utility cannot fix the drive, you may need to choose the Reinstall macOS option from the Recovery menu. This typically installs a fresh copy of the operating system without deleting your personal files. If you are worried about your data, try connecting your MacBook to another Mac using Target Disk Mode. Hold the T key during startup to make your MacBook appear as an external drive on the other computer, allowing you to copy your precious files before performing more invasive repairs.