ou can use an external drive or secondary volume as a startup disk from which to install the Mac operating system.
These advanced steps are primarily for system administrators and other experienced users who are familiar with entering commands in Terminal.
You don’t need a bootable installer to upgrade macOS or reinstall macOS, but it can be useful if you want to install macOS on multiple computers without downloading the installer each time, or you’re unable to install a compatible macOS from the Finder or macOS Recovery.
What you need to create a bootable installer
- USB flash drive or other secondary volume with at least 14GB of available storage, formatted as Mac OS Extended.
- Installer for OS X El Capitan or later. To get the full installer, your Mac must be using the latest version of OS X El Capitan, the latest version of macOS Sierra, or any later version of macOS. Download from a Mac that is compatible with the macOS you’re downloading. Enterprise administrators: download from Apple, not a locally hosted update server.
Use Terminal to create the bootable installer
- Plug in the USB flash drive or other volume that you’re using for the bootable installer.
- Open Terminal, which is in the Utilities folder of your Applications folder.
- Type or paste one of the commands below into Terminal, then press Return to enter the command. Each command assumes that the installer is in your Applications folder, and MyVolume is the name of the USB flash drive or other volume you’re using. If the volume has a different name, replace
MyVolumein the command with the name of your volume. - When prompted, type your administrator password. Terminal doesn’t show any characters as you type. Then press Return.
- When prompted, type Y to confirm that you want to erase the volume, then press Return. Terminal shows the progress as the volume is erased.
- After the volume is erased, you may see an alert that Terminal would like to access files on a removable volume. Click OK to allow the copy to proceed.
- When Terminal says that it’s done, the volume will have the same name as the installer you downloaded, such as Install macOS Monterey. You can now quit Terminal and eject the volume.
Commands
Depending on which macOS you downloaded, enter one of the following commands in Terminal as instructed above.
If your Mac is using macOS Sierra or earlier, the command should conclude with --applicationpath followed by the appropriate installer path, as shown in the command below for El Capitan.
Ventura
sudo /Applications/Install\ macOS\ Ventura.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
Monterey
sudo /Applications/Install\ macOS\ Monterey.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
Big Sur
sudo /Applications/Install\ macOS\ Big\ Sur.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
Catalina
sudo /Applications/Install\ macOS\ Catalina.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
Mojave
sudo /Applications/Install\ macOS\ Mojave.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
High Sierra
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume
El Capitan
sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app