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How to Make a Bootable High Sierra Installer
Storing an emergency backup copy of macOS on an external drive is the thing every Apple user should have. Here’s why: when something goes wrong, an emergency copy can rescue you and help recover your macOS. Forewarned is forearmed.
It’s much faster to use a bootable USB flash drive to install the operating system on several Macs. Creating a bootable drive with High Sierra installer is easy: basically, all you need is 16 GB of available storage space.
Launch the App Store, type High Sierra in the upper right search bar, and download the High Sierra installer. The file named Install macOS High Sierra will appear in the Applications folder once the download is completed. If you’ve already upgraded to High Sierra, the installer is automatically removed from that location. In this case, navigate to Purchased in the App Store and find the installer in the list.
What’s next? Get an external drive you want to save the installer on. While SSD would be a great option, a 16GB USB drive is enough when money is tight. The system will automatically reformat the drive to make it compatible with Mac. Change the name of your drive to HighSierra.
Note: Advanced steps mentioned below are intended for system administrators and experienced macOS users who know how to use the Terminal command line. Find more details on how to make a bootable copy of macOS here.
Create a Bootable High Sierra Installer in the Terminal
Once you have the external drive and the High Sierra installer, use the Terminal app to create a boot disk. Navigate to the Applications folder and open the Terminal from the list of utilities. You can also type Terminal in the Spotlight search and select the top search result.
Connect the HighSierra USB drive to your Mac.
Launch the Terminal (navigate to Applications>Utilities and open the Terminal app).
Paste the following command into the Terminal window
sudo /Applications/Install\ macOS\ High\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/HighSierra
You’ll be prompted to type your login password. Note, the characters you type aren’t displayed in the Terminal window. Enter the password and press Return.
You should receive a warning that your drive will be erased. Press Y to confirm.
The Terminal will erase your drive. Next, your Mac is most likely to ask you if you want to use the HighSierra USB drive for Time Machine backups. Select Don’t use and the Terminal app will copy the installer to the HighSierra drive.
After you see the process is done, quit the Terminal. Now your drive is ready to use.
4 Steps to Boot from the Installer Drive
It’s really easy to boot from the installer drive. Follow these quick step-by-step guide:
Plug the HighSierra drive into your Mac.
Turn on your Mac and hold down the Option key while your Mac boots.
Once you see a Startup Manager window, select the HighSierra drive from the list and press Return.
Select Install macOS in the macOS Utilities window.