How to boot a Mac from USB media Insert the USB boot media into an open USB slot. Press the Power button to turn on your Mac (or Restart your Mac if it's already on). When you hear the startup chime, press and hold the Option key. Holding that key gives you access to OS X's Startup. 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. The next time you start up or restart your computer, your Mac starts up using the operating system on the selected volume. Restart (or start) your Mac and hold down the option key. This will allow you to pick the USB drive to boot into. Once booted you can use the options to restore from a Time Machine backup, use Disk Utility to repair your hard drive, reinstall the OS, and get help online.
If you're still using a Mac OS X the time will come when your computer won't boot, or a problem may arise where you can't take control of the device, and booting from an OS X installation media will be required.
This is why it's recommended that you make a Mac OS X bootable USB when your Mac is in working conditions. However, if you find yourself on a scenario where your device (iMac, MacBook Pro, Air, Mac Pro or Mini) is not responding and you happen to have a Windows 10 device, then you can still be able to make a USB bootable installation media for your Mac OS X to reinstall the operating system using the Recovery Assistant.
These instructions will also work for Windows users who are running Mac OS X on a virtual machine and need to upgrade to the latest version. For instance, to OS X Yosemite.
Requirements
Before you dive into this guide, you'll need a few things:
- A broken Mac computer with Mac OS X.
- A trial copy of the TransMac software.
- One high quality USB flash drive with 16GB of storage.
- A copy of Apple's macOS (DMG file).
Now that you have all the necessary ingredients, you're ready to make a Mac OS X bootable USB using the DMG file of the operating system with the steps below.
Create Mac OS X bootable USB installation media
Before you can use TransMac, you first need to partition your USB flash drive with a GPT partition, as a normal MBR partition may not work. To do this, you'll need to use the Diskpart command-line utility on Windows 10.
Setting up GPT partition
Use these steps to set up a USB drive with a GPT partition:
Open Start on Windows 10.
Search for Command Prompt, right-click the top result and select the Run as Administrator option.
Type the following command to open Diskpart and press Enter:
Type the following command to determine the USB flash drive and press Enter:
Type the following command to select the storage and press Enter:
Quick tip: Theselect disk 1command as an example, but you have to replace 1 with the number of the flash drive you want to use.Type the following commands to delete everything from the USB thumb drive and press Enter: Remove mac spyware and adware.
Type the following command to convert the drive into a GPT partition and press Enter:
Type the following command to select the new partition and press Enter:
After you complete the steps, the USB flash drive from MBR to GPT format, you can use the steps below to create a bootable USB installation media to install Mac OS X.
Create USB install media
Use these steps to create a bootable media to install Mac OS X:
Download and install a copy of TransMac.
Quick note: TransMac is a paid software, but it has a 15-day trial solution, that give us more than enough time to move the DMG files to the USB drive from Windows. (If you want to support the developer, you can purchase the full version.)Insert the USB drive that you'll use to fix your installation of OS X. (Remember that all the data in the USB will be erased. Make sure you take off any important documents.)
Right-click the TransMac software icon and Run as administrator. (You'll be prompted to Enter Key or Run, because we'll be using it once, click the Run option.)
On the left pane, you'll see all the Windows PC drives listed, right-click the USB drive that you're intending to use to reinstall Apple's OS X and select the Restore with Disk Image option.
In the warning dialog box, click the Yes button.
Use the Restore Disk Image to Drive dialog box to browse for the DMG file with the installation files for Mac OS X Yosemite in this case, and click the OK button to create a bootable USB of the operating system.
Now, you'll have to wait a long time. No kidding. It could take one or two hours to complete the process depending on your computer and other variables.
Once your bootable USB installation media is ready, remove it and insert it into your Mac, power it on, holding down the Option key, and select the USB you just created to reinstall Mac OS X.
If you're having issues trying to create a bootable media, you can get a USB flash drive that comes with Mac OSX ready to install.
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
Find the appropriate download link in the upgrade instructions for each macOS version:
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
- 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.
- Open Terminal, which is in the Utilities folder of your Applications folder.
- 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
MyVolumein these commands with the name of your volume.
Catalina:*
Mojave:*
High Sierra:*
El Capitan: - Press Return after typing the command.
- When prompted, type your administrator password and press Return again. Terminal doesn't show any characters as you type your password.
- When prompted, type
Yto confirm that you want to erase the volume, then press Return. Terminal shows the progress as the bootable installer is created. - 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.
Use the bootable installer
After creating the bootable installer, follow these steps to use it:
- Plug the bootable installer into a compatible Mac.
- 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. - Choose your language, if prompted.
- 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.
- Select Install macOS (or Install OS X) from the Utilities window, then click Continue and follow the onscreen instructions.
Learn more
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:
Start Mac From Usb
Mojave:
High Sierra:
Start Mac From Bootable Usb
El Capitan:
