Follow these instructions to create a bootable USB installer for Apple Mac OS 10.10 Yosemite.
Prepare the USB Flash Drive
Insert a blank USB flash drive of 8GB or larger, but not unnecessarily too large since it would be wasted space. Run the Disk Utility program found under Applications in the Utilities folder. Then follow these steps.
- In Disk Utility, select the USB flash drive.
- Click on Partition.
- Choose Partition Layout of 1 Partition.
- For the Format choose Mac OS Extended (Journaled)
- For the Name, type YosemiteUSB.
- Click the Options button and choose GUID and click the OK button.
- Click the Apply button to make these changes to the USB flash drive.
- When asked if you are sure, click the Partition button.
- Exit the Disk Utility program.
In the following steps, you’ll download the Yosemite files from the App store, but stop before clicking Continue when the installer starts.
- Go to the Yosemite page in the App store on your computer.
- Click Download.
- It will take a while for the download to complete. If you want to view a progress meter, during the download, click on the Updates tab in the App store.
- Once the download is complete, an Installer will run and there will be a Continue button. Don’t click that just yet. Instead, continue to the steps below. Then, once the installer is on a USB, you can store the USB somewhere safe and continue with the guided installation from the App Store installer.
Copy Yosemite to USB
In the following steps, Yosemite will be copied to the USB flash drive and it will be made into a bootable drive.
- Run the Terminal program found under Utilities.
- Select, Copy and then paste the following command into your Terminal window. Although the text wraps here, it will be copied and then pasted as a single command.
sudo ‘/Applications/Install OS X Yosemite.app/Contents/Resources/createinstallmedia’ –volume ‘/Volumes/YosemiteUSB’ –applicationpath ‘/Applications/Install OS X Yosemite.app’ –nointeraction
- Press Enter/Return after pasting in that command.
- You’ll be asked for your password. Enter it to continue. The process of copying the files may take 10 to 15 minutes depending on how fast or slow your computer is.
- The process will complete and you should see something like this in your Terminal window.
ComputerName:~ UserName$ sudo ‘/Applications/Install OS X Yosemite.app/Contents/Resources/createinstallmedia’ –volume ‘/Volumes/YosemiteUSB’ –applicationpath ‘/Applications/Install OS X Yosemite.app’ –nointeraction
Erasing Disk: 0%… 10%… 20%… 30%…100%…
Copying installer files to disk…
Making disk bootable…
Copying boot files…
If everything went okay, then type Exit and press Enter/Return to end your Terminal session. Then quit the Terminal program.
You now have a USB bootable installer for Yosemite. To use this, when starting an Apple computer hold down the Option key and then choose the drive. For now, you can eject it and keep it safe for whenever you need it.
Continue Yosemite Installation
If you’d like to continue the installation of Yosemite that was automatically launched after download from the App Store you can do that now by clicking Continue. Or, you can quit that installer and return later (it’s in your Applications). Once installed, the Yosemite installation files will be automatically deleted. This is why it’s important to create the USB bootable installation drive before you continue with the installation from the App Store.
There were a variety of sources used to create the above non-visual instructions. The most helpful article was on iClarified, and it includes images for those who find that useful.