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How to create a bootable macOS Mojave installer drive

Whenever Apple releases a new version of macOS, I like to create a bootable USB installation drive. I test different Macs, and when I need to upgrade those machines, it’s a lot more efficient to plug in the USB installer drive and run the installer, than to log into the App Store, download the 5GB OS installer, and then run it.

Because it’s so easy to create an external installation drive, it’s my preferred means of installing the OS. I keep it around for those time when I would rather use the drive than rely on booting in Recovery mode.

In this article I’ll go over the different ways you can create a bootable macOS Mojave installation drive. But before I give instructions on how to create the drive, I’ll go over the items you’ll need and how to get them.

Editor’s note: This tutorial was written using the first version of the macOS Mojave Public Beta. It will be updated whenever necessary when new versions of the Public Beta are released.

Macworld also has bootable-install-drive instructions for:

Get an external drive and maybe an adapter

The macOS Mojave Public Beta installer software is over 5GB. So you need a USB external drive that can hold that much data. The drive can be a thumb drive, hard drive, or SSD.

If you want to use a thumb drive, an 8GB drive works perfectly. I used an 8GB Kingston Data Traveler G4 ($9 on Amazon); it’s cheap and it supports USB 3.1, so it’s fast. I’ve also used a VisionTek 120GB USB 3.0 Pocket Solid State Drive ($100 on Amazon) and older USB thumb drives that support USB 2, which is slower, but works.

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A VisionTek USB drive coneccted to a 2017 MacBook Pro via Apple's USB-C VGA Multiport Adapter ($69).

If you have a 2015 or newer MacBook or a 2016 or newer MacBook Pro, you may need Apple’s $19 USB to USB-C adapter. This will allow you to connect a storage device that uses a USB type-A connector. If you don’t have an external drive and you have a USB-C Mac laptop, you could buy the SanDisk Ultra USB Type-C Flash Drive, which has a USB-C connector. You can get a 16GB version for $11 on Amazon.

When creating the boot drive, the storage device is reformatted, so there’s no need to format the drive beforehand.

Get the macOS Mojave installer software

In order to get the Mojave installer, you need to sign up for the Apple Beta Software Program. Once you’re enrolled, Apple will give you access to the the Mojave installer in the App Store. If you launch the App Store app and look for it in the Updates section, you won’t find it.

Note that if you decide to participate in the Beta Software Program, there is a policy that Apple asks you to agree to. And keep in mind that this is beta software, so you could run into problems witht he OS and with the app that you use.

You can read the information to learn more about Mojave. When you’re ready to download the software, click the Download button under the icon on the upper left. (If you’ve already downloaded the installer, the button will say Open instead of Download.)

macos mojave beta app store Apple

Once the download is complete, the installer will launch automatically. But don’t continue with the installation. Instead, press Command-Q on your keyboard to quit the installer.

The Mojave installer app will be in your Applications folder, so you can go there and launch it later to upgrade your Mac to the new operating system.

Make a bootable installer drive: The quick way

I used a free app called Install Disk Creator to make the installation drive. There’s another app called Diskmaker X, but at the time of this writing I wasn’t able to make it work with the Mojave Public Beta installer.

Download Install Disk Creator by clicking on the link above. When the download is done, you can move it over to your Applications folder. Then follow these steps to create your bootable macOS Mojave drive.

1. Connect your drive to your Mac. It’s OK if it’s not formatted as a Mac drive. The app will reformat it.

2. Launch Install Disk Creator.

3. In the main window, you’ll see a pop-up menu under Select the volume to become the installer. Click on the menu and select your drive.

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The main window of Install Disk Creator.

4. Under the pop-up menu, you’ll see Select the OS X installer. (macOS used to be called OS X.) If you have only the Mojave Beta installer on your Mac, Install Disk Creator will automatically select it. If you have other macOS installers, you need to click on Select the OS X installer and select the Mojave installer.

5. When you’re ready, click Create installer. Your Mac may tell you that Install Disk Creator wants to make changes, and you need to enter your user name and password. After you do this, the app will take a few minutes to create the boot drive. A progress bar. appears at the bottom of the Install Disk Create window.

When the app is done, the installer is ready to use.

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Make a bootable installer drive: The longer way using the Terminal

You don’t need to use Install Disk Creator to create a bootable installer. You can do it in the Terminal and it’s easy. Here are the instructions.

1. Connect the external drive to your Mac. In these instructions, I use Untitled as the name of the external drive. If your drive is named something else, you need to change Untitled to the name of your drive.

2. Launch Terminal (/Applications/Utilities/Terminal.app).

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The Terminal. Don’t worry if your screen doesn’t look like this. I changed it in the Terminal settings, and you can too. In Terminal, select Terminal > Preferences > Profiles, click on the one you like, and then click on the Default button. 

3. Select and copy the following:
sudo /Applications/Install\ macOS\ Mojave\ Beta.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled -- /Applications/Install\ macOS\ Mojave\ Beta.app

4. Go back to Terminal and paste the copied code at the prompt. Press Return.

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Paste the code you copied into the Terminal then press Return. You'll be asked about erasing the disk.

5. Terminal will warn you that your external drive needs to be erased. To proceed, type Y at the prompt and press Return.

6. You’ll see that Terminal erases your drive and then copies the installer file to your drive. This will take a few minutes.

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7. After copying, Terminal is done. You should see Terminal display a “Copy complete” and Done notice. You can quit Terminal and your drive is ready for use.

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How to boot from the installer drive

1. Plug your external drive into your Mac.

2. Power up (or restart) your Mac. Press down on the Option key while the Mac boots.

3. After a few moments, your Mac should display the Startup Manager, which will show you the available boot drives. Click on the external drive and press Return. (You don’t need to select a network to proceed.)

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4. Your Mac will display a macOS Utilites window. If you want to install Mojave and leave the data intact, select Install macOS. If you want to start over and wipe out the data, you need to go into Disk Utility to reformat the internal drive first, and then install macOS Mojave.

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What to do when ‘this copy of the install OS X application cannot be verified’ or ‘the installer payload failed signature check’

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