Creating a bootable OS X installer

Modified on Fri, 1 Sep, 2017 at 1:18 PM

Things you will need to create this bootable USB flash drive:

at least a 12 GB USB flash drive
a mac that has Mac OS Sierra 10.12 already installed
your school sites apple id and password - this is needed just to download the Mac OS Sierra installer from the app store.

You can create a bootable flash drive to update a Mac's OS without having to log into the app store on each mac you need to update. Instead, this allows you to boot directly to the USB saving you time but also you can create as many of these bootable flash drives as you want. This can help if you have a lab full of Mac's or have multiple teachers that want to upgrade their computers to the most recent Mac OS.

Below you will find steps on how to create the bootable USB flash drive. After you create the USB bootable flash drive by following the first instructions titled "

How to create a bootable flash drive for Mac OS Sierra:" then you can choose to perform the Standard or Advanced options. The standard option includes the OS upgrade only and does not erase the hard drive. The advanced option will erase the hard drive first, when you do not need to save any data, and then complete a fresh install of the Mac OS.

How to create a bootable flash drive for Mac OS Sierra:

Open the App Store on your mac
Search for "Sierra" or "Mac OS"
Click Download
After a minute or so, click your launchpad app and you will see the download progress
When it is done it may automatically open the Installer Wizard but just minimize the window it is not needed
Plug in a USB flash drive at least 12 GB and rename the drive to Untilted - (If you see it appear on the desktop, remember the name of the USB drive as you will need this later. You can use the current name but sometimes different names can cause an issue for some reason. especially names with spaces or longer names. I have a less fail rate when using the name "untitled". So for this example that is what were using.)
Open your terminal app on your mac
Copy and paste the following command but do not hit enter yet:

sudo /Applications/Install\ macOS\ Sierra.app/Contents/Resources/createinstallmedia --volume /Volumes/MyVolume --applicationpath /Applications/Install\ macOS\ Sierra.app

In terminal, use the arrows on your keyboard to navigate through the command until you get to the word "MyVolume". You need to replace this name with the name of your USB drive. You can rename your USB drive to MyVolume if you would like.
Hit enter to exec
You should see the following:
Ready to start.
To continue we need to erase the disk at /Volumes/Untitled.
If you wish to continue type (Y) then press return: y
Erasing Disk: 0%... 10%... 20%... 30%...100%... (<-- This will reformat the flash drive)
Copying installer files to disk...
Copy complete.
Making disk bootable...
Copying boot files...
Copy complete.

Standard Upgrade/Install - this does not erase any data of the hard drive but instead updates the OS to Sierra 10.12

Make sure to eject your USB flash drive properly. (Meaning don't just pull the drive out. You need to either control click the drive icon on the desktop and choose "eject" or drag the drive to the trash which turns into EJECT and then you can pull the drive out.)
Insert the drive into the mac that you would like to update
Restart the mac
Immediately hold down the "option" key on the keyboard
Select your USB drive from the Disk Menu. Probably called by default "Install Mac OS sierra".
Your USB drive will boot your mac and take you to a main menu that looks just like the recovery OS X Utilities main menu (this may take a while as you're booting from a USB flash drive)
At the main menu, choose "reinstall OS"
Follow the onscreen instructions to continue the process until complete

Advanced Upgrade/install - includes erasing the hard drive in order to perform a fresh install of Mac OS Sierra 10.12

Make sure to eject your USB flash drive properly. (Meaning don't just pull the drive out. You need to either control click the drive icon on the desktop and choose "eject" or drag the drive to the trash which turns into EJECT and then you can pull the drive out.)
Insert the drive into the mac that you would like to update
Restart the mac
Immediately hold down the "option" key on the keyboard
Select your USB drive from the Disk Menu. Probably called by default "Install Mac OS sierra".
Your USB drive will boot your mac and take you to a main menu that looks just like the recovery OS X Utilities main menu (this may take a while as your booting from a USB flash drive)
At the main menu, choose "Disk utility"
In Disk utility, on the left side menu, choose your primary drive which by default is called "Macintosh HD"
On the right side menu, choose erase
Enter a name for your primary hard drive. You can use the usual default of Macintosh HD
Choose the Format "Mac OS Extended (Journaled)
Click Erase
Wait for the erase process to finish
Close Disk Utility
Back on the main menu, choose "reinstall OS"
Follow the onscreen instructions to continue the process until complete

For older versions lower than 10.12 Sierra see below.

This applies to OS Mavericks or Higher! The example below is for Yosemite but just replace any "Yosemite" text with "Mavericks" text.

You will need the following:

USB Drive ( at least 8GB)

The OS Yosemite app download from the App Store (If you have currently installed Yosemite, you may need to re-download Yosemite from the App store within the "purchases" section. This is because once you use the Yosemite installer app for the first time, the file needed for this walkthrough will disappear.

Connect to your Mac a properly formatted 8GB (or larger) drive, and rename the drive Untitled. (The Terminal command used here assumes the drive is named Untitled, you can technically call it whatever you would like) Also, make sure the Yosemite installer, called Install OS X Yosemite.app, is in its default location in your main Applications folder (/Applications). This means that if you moved it before installing Yosemite, you need to move it back before making your installer drive.

Select the text of this Terminal command and copy it:

sudo /Applications/Install\ OS\ X\ Yosemite.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ Yosemite.app --nointeraction

Launch Terminal (in /Applications/Utilities).
Warning: This step will erase the destination drive or partition, so make sure that it doesn’t contain any valuable data. Paste the copied command into Terminal and press Return.
Type your admin-level account password when prompted, and then press Return.
The Terminal window displays the progress of the process, in a very Terminal sort of way, by displaying a textual representation of a progress bar: Erasing Disk: 0%... 10 percent...20 percent... and so on. The program then tells you it’s copying the installer files, making the disk bootable, and copying boot files. Wait until you see the text Copy Complete. Done. which could take as long as 20 or 30 minutes, depending on how fast your Mac can copy data to your destination drive.

Note* - In Step #1, if you choose not to use the name "Untitled" for your drive, just make sure you replace the text "Untitled" with the correct name in the Terminal command above.