How can a new operating system be created

Reinstall macOS

Use macOS Recovery to reinstall the Mac operating system.

Start the computer with macOS Recovery

Apple chip

Turn on and hold the Mac On / off switch until the startup options window appears. Click the gear icon labeled Options, then click Next.

Intel processor

Make sure your Mac has an internet connection. Then turn on your Mac and stop immediately Command (⌘) -R until you see an Apple logo or other picture.

When prompted to select a user for whom you know the password, select the user, click Next, and enter their administrator password.

Reinstall macOS

In the macOS Recovery Utilities window, select Reinstall macOS. Then click "Next" and follow the on-screen instructions.

Follow these instructions during installation:

  • When the installer asks you to unlock the volume, enter the password that you use to log into your Mac.
  • If the installer doesn't recognize the volume you want, or a message stating that it cannot install on your computer or volume, you may need to erase your volume first.
  • If the installer gives you a choice between installing on Macintosh HD and Macintosh HD-Data, select Macintosh HD.
  • Wait for the installation to complete without hibernating or exiting your Mac. Your Mac may restart, show a progress bar multiple times, and the screen may go blank for several minutes.

After the installation is complete, your Mac may restart using a setup assistant. To sell, trade, or give away your Mac, press Command-Q to exit the wizard without completing setup. Then click on "Turn off". When the new owner starts the Mac, they can set up the device with their data.

Other macOS installation options

If you are installing macOS from recovery, this will be the latest version of the most recently installed macOS, with the following exceptions:

  • On an Intel-based Mac: If at startup Shift-Option-Command-R you will be offered the macOS that came with your Mac or the next available version. When you start Option-Command-R in most cases, you will be offered the latest version of macOS that is compatible with your Mac. Otherwise, you will be offered the version of macOS that your Mac originally came with, or the version closest to the original version that is still available.
  • If your Mac's motherboard has just been replaced, you may only be offered the latest version of macOS that is compatible with your Mac. If you've just erased all of your startup disk, you may only be offered the macOS that came with your Mac or the next available version.

You can also use the following methods to install macOS, if the version of macOS is compatible with your Mac:

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