How to Make a Bootable USB on a Mac

A bootable USB drive is a handy tool if you need to reinstall OS X Yosemite on your Mac, or if you're updating other Macs. To create this drive, download the OS X Yosemite installer from the App store and then use a specific command in Terminal to load it onto the USB disk.

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Download the OS X Installation file to create a bootable USB disk.
credit: Image courtesy of Apple.

You need a USB disk that is 8GB or larger. OS X formats the drive as part of the process, so make sure to copy any files that are already on the USB drive.

Step

Launch the App Store app on your Mac computer and download the OS X Yosemite installer. To find the installer, type "Yosemite" in the Search field and click the OS X Yosemite "Download" button.

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Download OS X Yosemite.
credit: Image courtesy of Apple.

Step

When a dialog box opens warning that you already have Yosemite, click "Continue." Enter your Apple ID password if prompted. The download can take an hour or more, depending on your Internet speed.

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Quit the Install OS X utility.
credit: Image courtesy of Apple.

Step

Close the Install OS X utility as soon as it opens by pressing "Command-X" or by selecting "Quit Install X" from the File menu.

Step

Note that the OS X Yosemite installer is located in the Applications folder. Don't move this file until you have finished creating your USB boot disk.

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Launch Terminal.
credit: Image courtesy of Apple.

Step

Insert the USB disk into your Mac and launch Terminal. To launch it quickly, just type "Terminal" in Spotlight search.

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Enter this command in Terminal.
credit: Image courtesy of Apple.

Step

Copy this single line of code and paste it in Terminal:

Step

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

Step

This command creates an installation disk from the USB drive using the Yosemite.app file. The option "--nointeraction" sets Terminal to not to prompt you for action, such as requiring you to press "Y" to continue.

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OS X begins creating a bootable installation disk.
credit: Image courtesy of Apple.

Step

Press the "Enter" key. Note that this command requires that the "Yosemite.app" file be in the Applications folder. To copy the files and configure the drive takes about a half an hour.

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Eject the USB drive.
credit: Image courtesy of Apple.

Step

Close Terminal when it is finished creating the drive and returns you to the command prompt. Click the "Eject" button beside the USB drive in Finder. Turn off the Mac, insert the USB drive and re-power on the Mac. The Mac will boot from the USB drive and prompt you to install OS X Yosemite.