How Create a MacOS Sierra Bootable Installer Drive

In here you'll learn how to make a macOS Sierra 10.12 bootable install drive just by using the current Developer beta preview release and a working USB flash drive.

But before we proceed to the nitty gritty stuff, here's what you need first in creating the MacOS Sierra Bootable Installer Drive:

A 16GB or larger USB Flash Drive
MacOS Sierra 10.12 Beta Installer Application (App Store / Developer Center)

Note: The flash drive could be anything but for easy of use, a flash thumb drive is recommended. Also, the MacOS Sierra installer application must be on the /Applications/ folder. Lastly, you’ll want to run through the bootable installer creation process before installing MacOS Sierra, because the installer application deletes itself once MacOS Sierra has completed installing. If you already ran the installer, you’d need to re-download MacOS Sierra and be sure it’s in /Applications/ folder.

Now let's begin.

Step 1: Connect your USB to your mac. Take note that this USB will be formatted so ensure that nothing is of any important on it.

Step 2: Rename the USB drive to "SierraInstaller" (without spaces).

Step 3: Launch the terminal application which is located in /Applications/Utilities/ folder and input the following command lines:

For MacOS Sierra 10.12 Developer Preview Beta

sudo /Applications/Install\ 10.12\ Developer\ Preview.app/Contents/Resources/createinstallmedia --volume /Volumes/SierraInstaller --applicationpath /Applications/Install\ 10.12\ Developer\ Preview.app --nointeraction &&say Done

Step 4: Check the syntax in Terminal if it's accurate and then, press the Retuen key and input your admin password. This will then start the Sierra boot drive creation process which can take a while to finish.

Step 5: After that, the command line will update with various messages and progress. When you see the "Done" message, it means that the MacOS Sierra Boot installer drive has been successfully created.

“Erasing Disk: 0%… 10%… 20%… 30%…100%…
Copying installer files to disk…
Copy complete.
Making disk bootable…
Copying boot files…
Copy complete.
Done.”

Step 6: Quit the terminal after you finished all the steps above.

Once done, you can now freely update an existing installation to MacOS Sierra using your USB drive or, you can reboot your Mac and hold down the "Option" key to select the macOS Sierra 10.12 installer as your bootable installation volume. Of course, just make sure that the Mac you are trying to update is compatible with the MacOS Sierra.

Lastly, proceed with the installation of macOS Sierra as any other Mac OS X system software installation.

Congratulations! You have finished creating a MacOS Sierra bootable installer drive!