This covers the start up mode using Command + R keys.
Note: Recovery Mode takes longer to boot - this is normal.
Things you can do in Recovery Mode:
- Restore from Time Machine back up
- Reinstall the last macOS that was previously installed
- Go to Apple Support help online
- Use Disk Utility to partition, repair, erase, format drives
- Add or remove an EFI password (must know password if removing)
- Troubleshoot network connection
- Open Terminal from Recovery Partition (reset user password, disable/enable SIP, change date, etc.)
- Select a different startup disk
- See the Installer Log
If you cannot startup in Recovery Mode by this startup combination, the recovery partition may be corrupt or non-existent, keyboard may be faulty, or the Mac was running an older OS (10.6 or older). Try a wired keyboard, Internet Recovery, a different startup disk, or bootable installer.