How to access Mac Recovery Mode to Fix Startup Problem and Reinstall macOS

If Mac won’t be able to boot up, follow below steps to access to Mac Recovery Mode that you can use to diagnose and fix startup issues or reinstall macOS completely.

macOS recovery mode utilities
macOS recovery mode utilities

Content Summary

Boot into Standard Recovery Mode
Boot into Internet Recovery Mode
Restore backup from Time Machine in macOS Recovery Mode
Run First Aid From Recovery Partition
Reinstall macOS
Source

Boot into Standard Recovery Mode

Step 1: In the Apple menu, choose Restart or power on Mac.

Step 2: Restart it by holding down Command(⌘) + R immediately upon hearing the startup chime.

Step 3: You’ll see the macOS Utilities window.

Step 4: Recovery Mode provides four service options: Restore from Time Machine Backup, get help online from Apple Support site, fix disk problems with Disk Utility and reinstall macOS.

Boot into Internet Recovery Mode

Step 1: In the Apple menu, choose Restart or power on Mac.

Step 2: Restart it by holding down Command(⌘) + Option(⌥) + R immediately upon hearing the startup chime. Hold the keys until the animated globe appears on the screen with message Starting Internet Recovery. This may take a while.

macOS Internet Recovery Mode
macOS Internet Recovery Mode

Step 3: Wi-Fi menu appears. Internet Recovery needs an Internet connection to load the recovery tools from Apple’s servers. Click the menu to display the available Wi-Fi networks and then select one to connect to.

Step 4: After Mac has connected to the Wi-Fi network, it’ll download a recovery system image from Apple’s servers and start from it, giving you access to the recovery tools.

Step 5: You’ll see the macOS Utilities window.

Step 6: Recovery Mode provides four service options: Restore from Time Machine Backup, get help online from Apple Support site, fix disk problems with Disk Utility and reinstall macOS.

Note: Advantages of booting into Internet Recovery Mode compare with Standard Recovery Mode: Internet Recovery Mode permits you to reinstall the macOS version that was factory-preloaded on your Mac at the time of purchase by downloading the version of macOS that originally came with your Mac, which in most cases won’t be the most up-to-date macOS version available. Additionally, Internet Recovery will automatically run a quick test of the Mac’s memory and disks to check for hardware issues. You should use Internet Recovery Mode if your Mac’s internal disk is damaged or you’ve replaced it with a faster, more capacious model and you’ve forgotten to create a bootable version of El Capitan on USB media.

Restore backup from Time Machine in macOS Recovery Mode

Step 1: Restart your Mac.

Step 2: While the startup disc is waking up, hold down Command(⌘) + R keys simultaneously to boot into macOS Recovery.

Step 3: Select Restore from Time Machine Backup.

Step 4: Click Continue.

Step 5: Click Continue on the Restore Your System page.

Step 6: Select your Time Machine Backup.

Step 7: Click Continue.

Step 8: Select the most recent backup of your Mac’s hard drive.

Step 9: Click Continue. Your mac will restore the Time Machine backup and then restart once it is finished.

Run First Aid From Recovery Partition

Recovery Partition on all macOS comes with Disk Utility which can run First Aid function attempt to fix on a drive that may be corrupted. However, Disk Utility won’t be able to fix a failing disk.

macOS Disk Utility First Aid
macOS Disk Utility First Aid

After First Aid completed successfully, try to boot into macOS again. If Disk Utility wasn’t able to fix all problems, try to run it again. If often can fix more on the second run-through.

Reinstall macOS

Step 1: Enter macOS recovery mode with following option key combination:
Command(⌘) + R: Install the latest macOS that was installed on your Mac. Note that if you’re selling or giving away a Mac that is using OS X El Capitan or earlier you should also use Command(⌘) + R – this will make sure that the installation isn’t associated with your Apple ID.
Option + Command(⌘) + R: Upgrade to the latest macOS compatible with your Mac.
Shift + Option + Command(⌘) + R: Install the macOS that came with your Mac or the closest to that version if it isn’t available as a download.

Step 2: On the Recovery Mode splash screen, select Reinstall macOS which will execute the macOS installer.

Step 3: Agree to the terms of service and choose the drive to which you want to install.

Step 4: The installation process will run.

Step 5: Once the installation process completed, you should boot into a fresh copy of macOS.

Reinstall macOS via recovery mode
Reinstall macOS via recovery mode

Source

Apple Support: About macOS Recovery
Apple Support: How to reinstall macOS from macOS Recovery