Learn how to reinstall your Mac operating system to built-in or external media from the macOS Recovery partition, which makes it easy to reinstall your Mac operating system, even if you have to erase your startup disk first.
All that is needed is an Internet connection. If a wireless network is available, you can select it from the Wi-Fi menu in the menu bar.
This menu is also available in macOS Recovery Mode.
ATTENTION! If Find My Mac was activated on your Mac, then after reinstallation the system will ask you to enter the Apple ID to which the device is linked.
Run from the macOS recovery partition
To start from the macOS recovery partition, press and hold one of the following keyboard shortcuts as soon as you turn on your Mac.
In general, Command + R is the recommended keyboard shortcut, especially if you’ve never installed macOS Sierra 10.12.4 or later.
Cmd (⌘) + R – Installs the latest version of macOS that was installed on this Mac.
Cmd + Option (Alt) + R – Update to the latest version of macOS that is compatible with your Mac.
Cmd + Option (Alt) + Shift + R – Install the macOS that came with your Mac or the closest version available (available starting with version 10.12.4).
Release the keys when you see the Apple logo, spinning globe, or prompt for the firmware password.
The appearance of the Utilities window means that the launch from the macOS recovery partition has been completed.
Decide whether to erase (format) the drive.
The usual reinstallation option will keep all user data in place, updating only the OS. By selecting Disk Utility, you can completely erase the boot volume.
If the second system is Windows, the Boot Camp partition can be left unchanged.
Select Disk Utility and click Continue.
Select your startup disk (usually the Macintosh HD, which is located at the very top left) and click on the “Erase” button at the top of the screen.
In the window that appears, specify the name (optional) and APFS format (for computers with macOS Sierra installed and an older version of the OS, select Mac OS Extended).
Click “Erase” at the bottom right of the window.
Install macOS
In the utilities window, select Reinstall macOS (Reinstall OS X).
Click “Continue” and follow the on-screen instructions to select a drive and begin installation.
If the installer asks you to unlock your drive, enter the password you use to sign in to your Mac.
If the installer does not see the disk or reports that it cannot be installed on this computer or volume, you may need to clean disk
Wait for the installation to complete without putting your Mac to sleep or closing the lid.
During the installation process, your Mac may restart several times and display a progress bar, and the screen may remain blank for several minutes.
If Setup Assistant appears after you restart, but you plan to sell or give away your Mac, press Command+Q to exit Setup Assistant without completing the setup process.
Then click “Turn off”. When the new owner starts up their Mac, they can enter their information during setup.
