How to Create A Bootable USB Drive on Mac

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There are times when having a bootable USB drive for Mac is important. There is also an argument to be made to have an Apple backup available at all times. Here, we’ll walk you though why you may want to do so, and how to backup Mac.

What is a Bootable USB or External Drive?

Simply stated, a bootable USB Mac drive is one that has a version (or versions) of macOS available on a disk that isn’t your machine. Whether it’s an external hard drive or a USB ‘thumb’ drive, both are considered bootable drives.

For the sake of clarity, we’ll simply refer to any external drive as a USB drive.

Before you begin, you’ll need to download the macOS version you’d like to use directly from Apple. It will download directly to your Applications folder; if your Mac starts to try to download and install the version of macOS you downloaded, simply quit the installation process.

How to Backup Mac to External Hard Drive

Curious how to create a bootable external drive for Mac? We’ve got you covered. First, you’ll need a USB drive, preferably one that is formatted to macOS Extended for any macOS backup to serve as your startup disk creator. Once you’ve done that, connect the USB drive to your machine, open the Terminal application on your Mac. Depending on the version of macOS you downloaded, enter one of the following commands:

  • 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
  • Sierra: sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ Sierra.app
  • El Capitan: sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app
Note: If your USB drive has a unique name, replace ‘MyVolume’ in the command with the name of your USB drive. If you read the command, you’ll see your Mac is taking the version of macOS you downloaded from your Applications folder and placing it on your USB drive.

After entering the command, do the following:

  • Press ‘Return’ or ‘Enter’ on your keyboard
  • When prompted in Terminal, enter your administrator’s password
  • Press ‘Return’ or ‘Enter’ on your keyboard
  • When prompted in Terminal, type ‘y’ to confirm you’d like to erase the USB drive.

When finished, Terminal will show the volume has the same name as the installer you downloaded. You can now quit terminal and eject your USB Drive.


Create bootable installer with Terminal


How to Boot Your Mac from a USB Drive

Now that you’ve created a bootable installer for your Mac, you can use it to boot a Mac using a fresh install of macOS! Here’s how:

  • Plug the bootable USB drive into your Mac
  • Open Startup Manager (or Startup Disk)
  • Select your USB drive from the list
  • Press ‘Restart’

Your mac will now start up in recovery mode, using the version of macOS you downloaded. From here, it may ask you to choose your language, set up a WiFi network, and other startup functions. When prompted, select ‘Install macOS’ from the Utilities window, then click ‘Continue’ and follow any on-screen directions. This is how you install macOS from a USB.

Don’t Forget to Backup Your Files!

Before starting the process, be sure to back your files and folders up! You can do this manually by digging through your files and loading them onto a separate USB drive, but there’s a better way.

CleanMyMacX is an app that helps optimize your Mac for performance, and also gets rid of duplicate files. We highly suggest running this prior to any installation of macOS from a bootable USB drive.

Clean up storage


Backups are best accomplished using Disk Drill, which both backs up your files and folders (as well as applications) and saves them to an external source. It even checks for lost files so nothing goes missing accidentally.

One of the best backup and cloning apps is Get Backup Pro. It creates backups of your hard drive, complete with files and folders, and saves them to an external USB drive. It’s a lot like Apple’s Time Machine, but allows much better control, and has a better user interface.

Get Backup Pro also compresses your backups, allows for scheduling of automatic backups, and allows you to recover from an external drive onto any computer.

Conclusion

Having a USB drive with a ‘clean’ version of macOS is always a good idea. When things go amiss, it’s nice to have an easy way to start from scratch.

But this doesn’t transfer files, which is why we select Disk Drill and/or Get Backup Pro. Utilizing one (or both) will help your files stay somewhere safe, so you never have to worry. We also advocate for using CleanMyMacX before any backup, which helps ensure your system – and backups – are optimized.

Luckily, all three are available as part of a free seven-day trial of Setapp, along with dozens of other great apps for Mac. Give it a shot!

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