Apple announced its latest version of the OS for Macs at this year’s WWDC, and as we all know it is called macOS Sierra. While the final public release of the OS is still a few months away, the beta version of the OS is already up for grabs.
Whether you are a registered Apple developer or someone who is interested in trying out beta versions of the OS, Apple has you covered. You can download the beta version of macOS Sierra from Apple’s website using either your developer account or an account that was enrolled for beta testing. Once you have downloaded the OS, you will want to create a USB installer so that you can have a fresh-install of the OS on your machine.
Creating a bootable macOS Sierra USB installer is as easy as running a few commands through Terminal. Here’s the entire process for downloading and creating a bootable USB installer.
Download the macOS Sierra Public Beta Installer
Apple has made the public beta of the OS available for download on their Apple Beta website, and all you need to do is go there and log in with your account, and then click on the “macOS” tab followed by “Download” to start the OS download.
The OS should be downloaded like an app from the Mac App Store and will take a while to finish downloading as it is sized at around 4GB.
After it has been downloaded on your Mac, it should automatically launch for installation. At this point you need to close it by pressing the “Command + Q” key on your keyboard, as you are not going to install the OS this way. You are going to use a USB installer for the OS installation.
Getting Your USB Drive Ready for the Installer
You need to have a USB drive that has at least 8GB available on it. Also, the drive will be formatted, so make sure you back it up before proceeding.
1. Plug in your USB drive to your Mac.
2. Launch Disk Utility.
3. Select your USB drive in Disk Utility by clicking on it in the left panel and then clicking on the button that says “Erase”. This will erase the content of the drive.
4. A dialog box should appear asking how you would like to erase the drive. Here’s what you need to select in the dialog box:
- Name – enter “macOSInstaller” (without quotes) as the name. If you are going to use other name, you will have to make changes to the commands in the steps below.
- Format – select “OS X Extended (Journaled)” as the drive format.
- Scheme – select “GUID Partition Map” as the scheme type.
Once you have selected these options, click on the “Erase” button to begin erasing the drive.
5. Your Mac should let you know when your drive is erased.
Creating a Bootable macOS Sierra Beta USB Installer
1. Launch Terminal on your Mac.
2. Enter the following command into Terminal and press Space. Do not press Enter just yet.
3. Navigate to the “Applications” folde, right-click on macOS Sierra Beta Installer and select “Show Package Contents.” It should let you see what is inside the installer package.
4. Click on “Contents” followed by “Resources” on the following screen to get to the resources folder in the package.
Inside the Resources folder is a file called “createinstallmedia.” Drag this file and drop it onto the Terminal window that is open. It will add the path of this file after the “sudo” command in Terminal.
5. After adding the path in the above step, add the following into the command and press Space. What you are doing here is specifying the name of the USB drive that should be created as a bootable macOS Sierra Beta installer.
6. Type in the following and press Space.
Then, open the Applications folder and drag and drop the macOS Sierra Beta installer you have downloaded from the App Store onto the Terminal window. The result should look like the following:
7. Finally, add the following into the command so that your Mac does not prompt you for anything.
8. Here’s what the full command looks like:
9. Press Enter on your keyboard to execute the command. Enter in your account password for it to be able to proceed. Your Mac should begin to erase the disk and write bootable OS files on it.
10. It should take anywhere from twenty to thirty minutes for the process to finish.
Your USB drive is now a bootable macOS Sierra Beta installer and you can now use it to boot your Mac for a clean install of the latest version of the OS.
Booting the Mac from the USB Installer
Now that the USB installer is ready, here’s how to do the actual installation:
1. Turn off your Mac by clicking on the Apple logo in the top-left corner of your screen and selecting “Shut Down…”.
2. Wait for your Mac to completely turn off.
3. Press the Power button on your keyboard to turn on your Mac. While your Mac is being turned on, hold down the “Option” key on your keyboard to choose a drive that your Mac should boot from.
4. When the boot menu appears, select your USB installer from the list and the macOS Sierra Beta installation should begin. Follow the on-screen instructions.
If you are one who has access to the public beta of macOS Sierra and would like to create a bootable USB installer of the same, the guide above should help you do exactly that.