General methodology:

  • Insert a USB flash drive into your computer. Your USB flash drive should plug into one of the rectangular or oval USB or USB-C ports on your computer’s housing. Traditional flash drives only fit one way, so don’t force the drive if it doesn’t fit.
    • If your Mac uses USB-C ports, your USB-C flash drive should fit any way in which you insert it.
    • The USB flash drive should be at least 8 gigabytes in space so that it can accommodate most operating system installation files.
  • Make sure that you have an ISO file. If you want to create a bootable USB drive on a Mac, you’ll need to have an ISO file (or an image file, if you’re backing up your computer’s hard drive) ready to drag and drop into Terminal.

    • This is different than how Windows handles bootable flash drives, since you can make a flash drive bootable and then save it for later when using Windows.
  • Open Spotlight

    . Click the magnifying glass icon in the top-right corner of the screen. A search bar will appear.

  • Type in terminal. This will search your Mac for the Terminal application.
  • Double-click Terminal

    . It’s a black box in the middle of the Spotlight search results. Doing so will open Terminal.

  • Open a list of connected drives. Type diskutil list into Terminal, then press Return.
  • Find your USB drive. Look for the USB drive that you plugged into your computer, then look at the USB drive’s name under the “IDENTIFIER” heading. You’ll usually find your USB drive under the “(external, physical)” heading near the bottom of the Terminal window.

    • Your USB flash drive’s name under the “IDENTIFIER” heading will normally be something like “disk1” or “disk2”.
  • Select the USB drive. Type diskutil unmountDisk /dev/disknumber—making sure to replace “disknumber” with the disk’s “IDENTIFIER” name and number (e.g., disk2)—into Terminal, then press Return.
  • Enter the formatting command. Type in sudo dd if= but don’t press the Return key just yet.
  • Drag the ISO file into the Terminal window. Click and drag the ISO file (or disk image file) that you want to boot into using the USB drive into the Terminal window. This will copy the file’s address into the Terminal command.

    • You can also type in the folder path to the ISO file.
  • Press the Space key. This will put a space at the end of the file’s address, making room for the next command.
  • Enter the rest of the command. Type in of=/dev/disknumber bs=1m, again making sure to replace “disknumber” with the USB flash drive’s number (e.g., disk2), and press Return.
  • Type in your password. This is the password that you use to log into your Mac. As you type, you’ll notice that the letters don’t appear in Terminal; this is normal.
  • Press Return. Doing so submits your password and prompts your Mac to begin creating a bootable USB flash drive with your selected ISO or image file.

    • This process can take several hours to complete, so just leave Terminal open and your Mac plugged in.