In Windows on your Mac, click in the right side of the taskbar, click the Boot Camp icon, then choose Boot Camp Control Panel. If a User Account Control dialog appears, click Yes. Select the startup disk that has the default operating system you want to use. If you want to start up using the default operating system now, click Restart. To restart a Mac computer, you have three choices: Press the power button (or press Control+Eject) and, when a dialog box appears, click the Restart button. Choose the Apple key and then click Restart. Press Control+Command+Eject (or Control+Command+Power button). You can change the startup disk your Mac automatically uses from System Preferences. From the Apple menu choose System Preferences. Click the Startup Disk icon in System Preferences, or choose View Startup Disk. Select your startup disk from the list of available volumes.

If your Mac desktop or Mac laptop is acting sluggish or programs are failing to run, you need to know how to restart your Mac computer. Restarting or rebooting your Mac essentially clears your computer’s memory and starts it up fresh. When you restart your computer, your Mac closes all running programs and offers to save any files you’re working on. After you choose to save any files, your Mac will finally boot up again.

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To restart a Mac computer, you have three choices:

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  • Press the power button (or press Control+Eject) and, when a dialog box appears, click the Restart button.
  • Choose the Apple key and then click Restart.
  • Press Control+Command+Eject (or Control+Command+Power button).

Pressing the Control+Command+Eject/Power button is the most reliable way to restart a Mac because it doesn’t rely on the Mac OS X operating system.

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Restarting a Mac computer isn’t the same as turning the computer on and off, which completely resets it. If you really want to make sure that your computer starts up correctly, turn it off, wait a few seconds, and then turn it on again. If you’re in a hurry, try restarting your Mac, and if that doesn’t fix the problem, you’ll have to turn it off and on again.

If your Mac freezes, restarting might not work. If your Mac is generally acting weird, restarting isn’t your only option. Macs are known not to need a lot of maintenance or troubleshooting, but if restarting (or rebooting) doesn’t work, consider some other basic troubleshooting options for your Mac.

These advanced steps are primarily for system administrators and others who are familiar with the command line. You don't need a bootable installer to upgrade macOS or reinstall macOS, but it can be useful when you want to install on multiple computers without downloading the installer each time.

Download macOS

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Find the appropriate download link in the upgrade instructions for each macOS version:

How to reboot your mac

macOS Catalina, macOS Mojave, ormacOS High Sierra
Installers for each of these macOS versions download directly to your Applications folder as an app named Install macOS Catalina, Install macOS Mojave, or Install macOS High Sierra. If the installer opens after downloading, quit it without continuing installation. Important: To get the correct installer, download from a Mac that is using macOS Sierra 10.12.5 or later, or El Capitan 10.11.6. Enterprise administrators, please download from Apple, not a locally hosted software-update server.

OS X El Capitan
El Capitan downloads as a disk image. On a Mac that is compatible with El Capitan, open the disk image and run the installer within, named InstallMacOSX.pkg. It installs an app named Install OS X El Capitan into your Applications folder. You will create the bootable installer from this app, not from the disk image or .pkg installer.

Use the 'createinstallmedia' command in Terminal

  1. Connect the USB flash drive or other volume that you're using for the bootable installer. Make sure that it has at least 12GB of available storage and is formatted as Mac OS Extended.
  2. Open Terminal, which is in the Utilities folder of your Applications folder.
  3. Type or paste one of the following commands in Terminal. These assume that the installer is still in your Applications folder, and MyVolume is the name of the USB flash drive or other volume you're using. If it has a different name, replace MyVolume in these commands with the name of your volume.
    Catalina:*
    Mojave:*

    High Sierra:*
    El Capitan:
  4. Press Return after typing the command.
  5. When prompted, type your administrator password and press Return again. Terminal doesn't show any characters as you type your password.
  6. When prompted, type Y to confirm that you want to erase the volume, then press Return. Terminal shows the progress as the bootable installer is created.
  7. When Terminal says that it's done, the volume will have the same name as the installer you downloaded, such as Install macOS Catalina. You can now quit Terminal and eject the volume.

* If your Mac is using macOS Sierra or earlier, include the --applicationpath argument, similar to the way this argument is used in the command for El Capitan.

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Use the bootable installer

After creating the bootable installer, follow these steps to use it:

  1. Plug the bootable installer into a compatible Mac.
  2. Use Startup Manager or Startup Disk preferences to select the bootable installer as the startup disk, then start up from it. Your Mac will start up to macOS Recovery.
    Learn about selecting a startup disk, including what to do if your Mac doesn't start up from it.
  3. Choose your language, if prompted.
  4. A bootable installer doesn't download macOS from the Internet, but it does require the Internet to get information specific to your Mac model, such as firmware updates. If you need to connect to a Wi-Fi network, use the Wi-Fi menu in the menu bar.
  5. Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.

Learn more

How To Reboot A Mac

For more information about the createinstallmedia command and the arguments that you can use with it, make sure that the macOS installer is in your Applications folder, then enter this path in Terminal:

Catalina:

Mojave:

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High Sierra:

El Capitan: